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• Integrating WIF with WCF Data Services

  - by cibrax

  A time ago I discussed how a custom REST Starter kit interceptor could be used to parse a SAML token in the Http Authorization header and wrap that into a ClaimsPrincipal that the WCF services could use. The thing is that code was initially created for Geneva framework, so it got deprecated quickly. I recently needed that piece of code for one of projects where I am currently working on so I decided to update it for WIF. As this interceptor can be injected in any host for WCF REST services, also represents an excellent solution for integrating claim-based security into WCF Data Services (previously known as ADO.NET Data Services). The interceptor basically expects a SAML token in the Authorization header. If a token is found, it is parsed and a new ClaimsPrincipal is initialized and injected in the WCF authorization context. public class SamlAuthenticationInterceptor : RequestInterceptor {   SecurityTokenHandlerCollection handlers;   public SamlAuthenticationInterceptor()     : base(false)   {     this.handlers = FederatedAuthentication.ServiceConfiguration.SecurityTokenHandlers;   }   public override void ProcessRequest(ref RequestContext requestContext)   {     SecurityToken token = ExtractCredentials(requestContext.RequestMessage);     if (token != null)     {       ClaimsIdentityCollection claims = handlers.ValidateToken(token);       var principal = new ClaimsPrincipal(claims);       InitializeSecurityContext(requestContext.RequestMessage, principal);     }     else     {       DenyAccess(ref requestContext);     }   }   private void DenyAccess(ref RequestContext requestContext)   {     Message reply = Message.CreateMessage(MessageVersion.None, null);     HttpResponseMessageProperty responseProperty = new HttpResponseMessageProperty() { StatusCode = HttpStatusCode.Unauthorized };     responseProperty.Headers.Add("WWW-Authenticate",           String.Format("Basic realm=\"{0}\"", ""));     reply.Properties[HttpResponseMessageProperty.Name] = responseProperty;     requestContext.Reply(reply);     requestContext = null;   }   private SecurityToken ExtractCredentials(Message requestMessage)   {     HttpRequestMessageProperty request = (HttpRequestMessageProperty)  requestMessage.Properties[HttpRequestMessageProperty.Name];     string authHeader = request.Headers["Authorization"];     if (authHeader != null && authHeader.Contains("<saml"))     {       XmlTextReader xmlReader = new XmlTextReader(new StringReader(authHeader));       var col = SecurityTokenHandlerCollection.CreateDefaultSecurityTokenHandlerCollection();       SecurityToken token = col.ReadToken(xmlReader);                                        return token;     }     return null;   }   private void InitializeSecurityContext(Message request, IPrincipal principal)   {     List<IAuthorizationPolicy> policies = new List<IAuthorizationPolicy>();     policies.Add(new PrincipalAuthorizationPolicy(principal));     ServiceSecurityContext securityContext = new ServiceSecurityContext(policies.AsReadOnly());     if (request.Properties.Security != null)     {       request.Properties.Security.ServiceSecurityContext = securityContext;     }     else     {       request.Properties.Security = new SecurityMessageProperty() { ServiceSecurityContext = securityContext };      }    }    class PrincipalAuthorizationPolicy : IAuthorizationPolicy    {      string id = Guid.NewGuid().ToString();      IPrincipal user;      public PrincipalAuthorizationPolicy(IPrincipal user)      {        this.user = user;      }      public ClaimSet Issuer      {        get { return ClaimSet.System; }      }      public string Id      {        get { return this.id; }      }      public bool Evaluate(EvaluationContext evaluationContext, ref object state)      {        evaluationContext.AddClaimSet(this, new DefaultClaimSet(System.IdentityModel.Claims.Claim.CreateNameClaim(user.Identity.Name)));        evaluationContext.Properties["Identities"] = new List<IIdentity>(new IIdentity[] { user.Identity });        evaluationContext.Properties["Principal"] = user;        return true;      }    } A WCF Data Service, as any other WCF Service, contains a service host where this interceptor can be injected. The following code illustrates how that can be done in the “svc” file. <%@ ServiceHost Language="C#" Debug="true" Service="ContactsDataService"                 Factory="AppServiceHostFactory" %> using System; using System.ServiceModel; using System.ServiceModel.Activation; using Microsoft.ServiceModel.Web; class AppServiceHostFactory : ServiceHostFactory {    protected override ServiceHost CreateServiceHost(Type serviceType, Uri[] baseAddresses)   {     WebServiceHost2 result = new WebServiceHost2(serviceType, true, baseAddresses);     result.Interceptors.Add(new SamlAuthenticationInterceptor());                 return result;   } } WCF Data Services includes an specific WCF host of out the box (DataServiceHost). However, the service is not affected at all if you replace it with a custom one as I am doing in the code above (WebServiceHost2 is part of the REST Starter kit). Finally, the client application needs to pass the SAML token somehow to the data service. In case you are using any Http client library for consuming the data service, that’s easy to do, you only need to include the SAML token as part of the “Authorization” header. If you are using the auto-generated data service proxy, a little piece of code is needed to inject a SAML token into the DataServiceContext instance. That class provides an event “SendingRequest” that any client application can leverage to include custom code that modified the Http request before it is sent to the service. So, you can easily create an extension method for the DataServiceContext that negotiates the SAML token with an existing STS, and adds that token as part of the “Authorization” header. public static class DataServiceContextExtensions {        public static void ConfigureFederatedCredentials(this DataServiceContext context, string baseStsAddress, string realm)   {     string address = string.Format(STSAddressFormat, baseStsAddress, realm);                  string token = NegotiateSecurityToken(address);     context.SendingRequest += (source, args) =>     {       args.RequestHeaders.Add("Authorization", token);     };   } private string NegotiateSecurityToken(string address) { } } I left the NegociateSecurityToken method empty for this extension as it depends pretty much on how you are negotiating tokens from an existing STS. In case you want to end-to-end REST solution that involves an Http endpoint for the STS, you should definitely take a look at the Thinktecture starter STS project in codeplex.

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• Implementing a generic repository for WCF data services

  - by cibrax

  The repository implementation I am going to discuss here is not exactly what someone would call repository in terms of DDD, but it is an abstraction layer that becomes handy at the moment of unit testing the code around this repository. In other words, you can easily create a mock to replace the real repository implementation. The WCF Data Services update for .NET 3.5 introduced a nice feature to support two way data bindings, which is very helpful for developing WPF or Silverlight based application but also for implementing the repository I am going to talk about. As part of this feature, the WCF Data Services Client library introduced a new collection DataServiceCollection<T> that implements INotifyPropertyChanged to notify the data context (DataServiceContext) about any change in the association links. This means that it is not longer necessary to manually set or remove the links in the data context when an item is added or removed from a collection. Before having this new collection, you basically used the following code to add a new item to a collection. Order order = new Order {   Name = "Foo" }; OrderItem item = new OrderItem {   Name = "bar",   UnitPrice = 10,   Qty = 1 }; var context = new OrderContext(); context.AddToOrders(order); context.AddToOrderItems(item); context.SetLink(item, "Order", order); context.SaveChanges(); Now, thanks to this new collection, everything is much simpler and similar to what you have in other ORMs like Entity Framework or L2S. Order order = new Order {   Name = "Foo" }; OrderItem item = new OrderItem {   Name = "bar",   UnitPrice = 10,   Qty = 1 }; order.Items.Add(item); var context = new OrderContext(); context.AddToOrders(order); context.SaveChanges(); In order to use this new feature, you first need to enable V2 in the data service, and then use some specific arguments in the datasvcutil tool (You can find more information about this new feature and how to use it in this post). DataSvcUtil /uri:"http://localhost:3655/MyDataService.svc/" /out:Reference.cs /dataservicecollection /version:2.0 Once you use those two arguments, the generated proxy classes will use DataServiceCollection<T> rather than a simple ObjectCollection<T>, which was the default collection in V1. There are some aspects that you need to know to use this feature correctly. 1. All the entities retrieved directly from the data context with a query track the changes and report those to the data context automatically. 2. A entity created with “new” does not track any change in the properties or associations. In order to enable change tracking in this entity, you need to do the following trick. public Order CreateOrder() {   var collection = new DataServiceCollection<Order>(this.context);   var order = new Order();   collection.Add(order);   return order; } You basically need to create a collection, and add the entity to that collection with the “Add” method to enable change tracking on that entity. 3. If you need to attach an existing entity (For example, if you created the entity with the “new” operator rather than retrieving it from the data context with a query) to a data context for tracking changes, you can use the “Load” method in the DataServiceCollection. var order = new Order {   Id = 1 }; var collection = new DataServiceCollection<Order>(this.context); collection.Load(order); In this case, the order with Id = 1 must exist on the data source exposed by the Data service. Otherwise, you will get an error because the entity did not exist. These cool extensions methods discussed by Stuart Leeks in this post to replace all the magic strings in the “Expand” operation with Expression Trees represent another feature I am going to use to implement this generic repository. Thanks to these extension methods, you could replace the following query with magic strings by a piece of code that only uses expressions. Magic strings, var customers = dataContext.Customers .Expand("Orders")         .Expand("Orders/Items") Expressions, var customers = dataContext.Customers .Expand(c => c.Orders.SubExpand(o => o.Items)) That query basically returns all the customers with their orders and order items. Ok, now that we have the automatic change tracking support and the expression support for explicitly loading entity associations, we are ready to create the repository. The interface for this repository looks like this,public interface IRepository { T Create<T>() where T : new(); void Update<T>(T entity); void Delete<T>(T entity); IQueryable<T> RetrieveAll<T>(params Expression<Func<T, object>>[] eagerProperties); IQueryable<T> Retrieve<T>(Expression<Func<T, bool>> predicate, params Expression<Func<T, object>>[] eagerProperties); void Attach<T>(T entity); void SaveChanges(); } The Retrieve and RetrieveAll methods are used to execute queries against the data service context. While both methods receive an array of expressions to load associations explicitly, only the Retrieve method receives a predicate representing the “where” clause. The following code represents the final implementation of this repository.public class DataServiceRepository: IRepository { ResourceRepositoryContext context; public DataServiceRepository() : this (new DataServiceContext()) { } public DataServiceRepository(DataServiceContext context) { this.context = context; } private static string ResolveEntitySet(Type type) { var entitySetAttribute = (EntitySetAttribute)type.GetCustomAttributes(typeof(EntitySetAttribute), true).FirstOrDefault(); if (entitySetAttribute != null) return entitySetAttribute.EntitySet; return null; } public T Create<T>() where T : new() { var collection = new DataServiceCollection<T>(this.context); var entity = new T(); collection.Add(entity); return entity; } public void Update<T>(T entity) { this.context.UpdateObject(entity); } public void Delete<T>(T entity) { this.context.DeleteObject(entity); } public void Attach<T>(T entity) { var collection = new DataServiceCollection<T>(this.context); collection.Load(entity); } public IQueryable<T> Retrieve<T>(Expression<Func<T, bool>> predicate, params Expression<Func<T, object>>[] eagerProperties) { var entitySet = ResolveEntitySet(typeof(T)); var query = context.CreateQuery<T>(entitySet); foreach (var e in eagerProperties) { query = query.Expand(e); } return query.Where(predicate); } public IQueryable<T> RetrieveAll<T>(params Expression<Func<T, object>>[] eagerProperties) { var entitySet = ResolveEntitySet(typeof(T)); var query = context.CreateQuery<T>(entitySet); foreach (var e in eagerProperties) { query = query.Expand(e); } return query; } public void SaveChanges() { this.context.SaveChanges(SaveChangesOptions.Batch); } } For instance, you can use the following code to retrieve customers with First name equal to “John”, and all their orders in a single call. repository.Retrieve<Customer>(    c => c.FirstName == “John”, //Where    c => c.Orders.SubExpand(o => o.Items)); In case, you want to have some pre-defined queries that you are going to use across several places, you can put them in an specific class. public static class CustomerQueries {   public static Expression<Func<Customer, bool>> LastNameEqualsTo(string lastName)   {     return c => c.LastName == lastName;   } } And then, use it with the repository. repository.Retrieve<Customer>(    CustomerQueries.LastNameEqualsTo("foo"),    c => c.Orders.SubExpand(o => o.Items));

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• ActAs and OnBehalfOf support in WIF

  - by cibrax

  I discussed a time ago how WIF supported a new WS-Trust 1.4 element, “ActAs”, and how that element could be used for authentication delegation.  The thing is that there is another feature in WS-Trust 1.4 that also becomes handy for this kind of scenario, and I did not mention in that last post, “OnBehalfOf”. Shiung Yong wrote an excellent summary about the difference of these two new features in this forum thread. He basically commented the following, “An ActAs RST element indicates that the requestor wants a token that contains claims about two distinct entities: the requestor, and an external entity represented by the token in the ActAs element. An OnBehalfOf RST element indicates that the requestor wants a token that contains claims only about one entity: the external entity represented by the token in the OnBehalfOf element. In short, ActAs feature is typically used in scenarios that require composite delegation, where the final recipient of the issued token can inspect the entire delegation chain and see not just the client, but all intermediaries to perform access control, auditing and other related activities based on the whole identity delegation chain. The ActAs feature is commonly used in multi-tiered systems to authenticate and pass information about identities between the tiers without having to pass this information at the application/business logic layer. OnBehalfOf feature is used in scenarios where only the identity of the original client is important and is effectively the same as identity impersonation feature available in the Windows OS today. When the OnBehalfOf is used the final recipient of the issued token can only see claims about the original client, and the information about intermediaries is not preserved. One common pattern where OnBehalfOf feature is used is the proxy pattern where the client cannot access the STS directly but is instead communicating through a proxy gateway. The proxy gateway authenticates the caller and puts information about him into the OnBehalfOf element of the RST message that it then sends to the real STS for processing. The resulting token is going to contain only claims related to the client of the proxy, making the proxy completely transparent and not visible to the receiver of the issued token.” Going back to WIF, “ActAs” and “OnBehalfOf” are both supported as extensions methods in the WCF client channel. public static class ChannelFactoryOperations {   public static T CreateChannelActingAs<T>(this ChannelFactory<T> factory,     SecurityToken actAs);     public static T CreateChannelOnBehalfOf<T>(this ChannelFactory<T> factory,     SecurityToken onBehalfOf); } Both methods receive the security token with the identity of the original caller.

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• AppFabric OutputCaching for ASP.NET Web API

  - by cibrax

  ASP.NET Web API does not provide any output caching capabilities out of the box other than the ones you would traditionally find in the ASP.NET caching module. Fortunately, Filip wrote a very nice library that you can use to decorate your Web API controller methods with an [OutputCaching] attribute, which is similar to the one you can find in ASP.NET MVC. This library provides a way to configure different persistence storages for the cached data, which uses memory by default. As part of this post, I will show how you can implement your own persistence provider for AppFabric in order to support distributed caching on web applications running on premises. Read more here  

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• Getting WCF Bindings and Behaviors from any config source

  - by cibrax

  The need of loading WCF bindings or behaviors from different sources such as files in a disk or databases is a common requirement when dealing with configuration either on the client side or the service side. The traditional way to accomplish this in WCF is loading everything from the standard configuration section (serviceModel section) or creating all the bindings and behaviors by hand in code. However, there is a solution in the middle that becomes handy when more flexibility is needed. This solution involves getting the configuration from any place, and use that configuration to automatically configure any existing binding or behavior instance created with code.  In order to configure a binding instance (System.ServiceModel.Channels.Binding) that you later inject in any endpoint on the client channel or the service host, you first need to get a binding configuration section from any configuration file (you can generate a temp file on the fly if you are using any other source for storing the configuration).  private BindingsSection GetBindingsSection(string path) { System.Configuration.Configuration config = System.Configuration.ConfigurationManager.OpenMappedExeConfiguration( new System.Configuration.ExeConfigurationFileMap() { ExeConfigFilename = path }, System.Configuration.ConfigurationUserLevel.None); var serviceModel = ServiceModelSectionGroup.GetSectionGroup(config); return serviceModel.Bindings; }   The BindingsSection contains a list of all the configured bindings in the serviceModel configuration section, so you can iterate through all the configured binding that get the one you need (You don’t need to have a complete serviceModel section, a section with the bindings only works).  public Binding ResolveBinding(string name) { BindingsSection section = GetBindingsSection(path); foreach (var bindingCollection in section.BindingCollections) { if (bindingCollection.ConfiguredBindings.Count > 0 && bindingCollection.ConfiguredBindings[0].Name == name) { var bindingElement = bindingCollection.ConfiguredBindings[0]; var binding = (Binding)Activator.CreateInstance(bindingCollection.BindingType); binding.Name = bindingElement.Name; bindingElement.ApplyConfiguration(binding); return binding; } } return null; }   The code above does just that, and also instantiates and configures the Binding object (System.ServiceModel.Channels.Binding) you are looking for. As you can see, the binding configuration element contains a method “ApplyConfiguration” that receives the binding instance that needs to be configured. A similar thing can be done for instance with the “Endpoint” behaviors. You first get the BehaviorsSection, and then, the behavior you want to use.  private BehaviorsSection GetBehaviorsSection(string path) { System.Configuration.Configuration config = System.Configuration.ConfigurationManager.OpenMappedExeConfiguration( new System.Configuration.ExeConfigurationFileMap() { ExeConfigFilename = path }, System.Configuration.ConfigurationUserLevel.None); var serviceModel = ServiceModelSectionGroup.GetSectionGroup(config); return serviceModel.Behaviors; }public List<IEndpointBehavior> ResolveEndpointBehavior(string name) { BehaviorsSection section = GetBehaviorsSection(path); List<IEndpointBehavior> endpointBehaviors = new List<IEndpointBehavior>(); if (section.EndpointBehaviors.Count > 0 && section.EndpointBehaviors[0].Name == name) { var behaviorCollectionElement = section.EndpointBehaviors[0]; foreach (BehaviorExtensionElement behaviorExtension in behaviorCollectionElement) { object extension = behaviorExtension.GetType().InvokeMember("CreateBehavior", BindingFlags.InvokeMethod | BindingFlags.NonPublic | BindingFlags.Instance, null, behaviorExtension, null); endpointBehaviors.Add((IEndpointBehavior)extension); } return endpointBehaviors; } return null; }   In this case, the code for creating the behavior instance is more tricky. First of all, a behavior in the configuration section actually represents a set of “IEndpoint” behaviors, and the behavior element you get from the configuration does not have any public method to configure an existing behavior instance. This last one only contains a protected method “CreateBehavior” that you can use for that purpose. Once you get this code implemented, a client channel can be easily configured as follows  var binding = resolver.ResolveBinding("MyBinding"); var behaviors = resolver.ResolveEndpointBehavior("MyBehavior"); SampleServiceClient client = new SampleServiceClient(binding, new EndpointAddress(new Uri("http://localhost:13749/SampleService.svc"), new DnsEndpointIdentity("localhost"))); foreach (var behavior in behaviors) { if(client.Endpoint.Behaviors.Contains(behavior.GetType())) { client.Endpoint.Behaviors.Remove(behavior.GetType()); } client.Endpoint.Behaviors.Add(behavior); }   The code above assumes that a configuration file (in any place) with a binding “MyBinding” and a behavior “MyBehavior” exists. That file can look like this,  <system.serviceModel> <bindings> <basicHttpBinding> <binding name="MyBinding"> <security mode="Transport"></security> </binding> </basicHttpBinding> </bindings> <behaviors> <endpointBehaviors> <behavior name="MyBehavior"> <clientCredentials> <windows/> </clientCredentials> </behavior> </endpointBehaviors> </behaviors> </system.serviceModel>   The same thing can be done of course in the service host if you want to manually configure the bindings and behaviors.  

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• Using the Katana Authentication handlers with NancyFx

  - by cibrax

  Once you write an OWIN Middleware service, it can be reused everywhere as long as OWIN is supported. In my last post, I discussed how you could write an Authentication Handler in Katana for Hawk (HMAC Authentication). Good news is NancyFx can be run as an OWIN handler, so you can use many of existing middleware services, including the ones that are ship with Katana. Running NancyFx as a OWIN handler is pretty straightforward, and discussed in detail as part of the NancyFx documentation here. After run the steps described there and you have the application working, only a few more steps are required to register the additional middleware services. The example bellow shows how the Startup class is modified to include Hawk authentication. public class Startup { public void Configuration(IAppBuilder app) { app.UseHawkAuthentication(new HawkAuthenticationOptions { Credentials = (id) => { return new HawkCredential { Id = "dh37fgj492je", Key = "werxhqb98rpaxn39848xrunpaw3489ruxnpa98w4rxn", Algorithm = "hmacsha256", User = "steve" }; } }); app.UseNancy(); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This code registers the Hawk Authentication Handler on top of the OWIN pipeline, so it will try to authenticate the calls before the request messages are passed over to NancyFx. The authentication handlers in Katana set the user principal in the OWIN environment using the key “server.User”. The following code shows how you can get that principal in a NancyFx module, public class HomeModule : NancyModule { public HomeModule() { Get["/"] = x => { var env = (IDictionary<string, object>)Context.Items[NancyOwinHost.RequestEnvironmentKey]; if (!env.ContainsKey("server.User") || env["server.User"] == null) { return HttpStatusCode.Unauthorized; } var identity = (ClaimsPrincipal)env["server.User"]; return "Hello " + identity.Identity.Name; }; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Thanks to OWIN, you don’t know any details of how these cross cutting concerns can be implemented in every possible web application framework.

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• OData to the rescue. Exposing the eventlog as a data feed

  - by cibrax

  In one of the project where I was working one, we used the Microsoft Enterprise Library Exception Application Block integration with WCF for logging all the technical issues on the services/backend in Windows Event Log. This application block worked like a charm, all the errors were correctly logged on the Event Log without even needing to modify the service code. However, we also needed to provide a quick way to expose all those events to the different system users so they could get access to all the them remotely. In just a couple of minutes I came up with a simple solution based on ADO.NET Data Services. ADO.NET data services is very powerful in this sense, you only need to provide a IQueryable implementation, and that’s all. You get a RESTful service with rich query support for free. In this sample, I used Linq to Objects to get the latest entries from the Event Log, and I also filter the entries by the category used by the Application Block to avoid loading unnecessary entries in memory. public class LogDataSource     {         string source;         public LogDataSource(string source)         {             this.source = source;         }         public LogDataSource()         {         }         public IQueryable<LogEntry> LogEntries         {             get { return GetEntries().AsQueryable().OrderBy(e => e.TimeGenerated); }         }         private IEnumerable<LogEntry> GetEntries()         {             var applicationLog = System.Diagnostics.EventLog.GetEventLogs().Where(e => e.Log == "Application")                 .FirstOrDefault();             var entries = new List<LogEntry>();             if (applicationLog != null)             {                 foreach (EventLogEntry entry in applicationLog.Entries)                 {                     if (source == null || entry.Source.Equals(source, StringComparison.InvariantCultureIgnoreCase))                     {                         entries.Add(new LogEntry                         {                             Category = entry.Category,                             EventID = entry.InstanceId,                             Message = entry.Message,                             TimeGenerated = entry.TimeGenerated,                             Source = entry.Source,                         });                     }                 }             }             return entries.OrderByDescending(e => e.TimeGenerated)                         .Take(200);         }     } LogEntry is class I created for this service to expose an Event Log Entry.     [EntityPropertyMappingAttribute("Source",         SyndicationItemProperty.Title,         SyndicationTextContentKind.Plaintext, true)]     [EntityPropertyMapping("Message",         SyndicationItemProperty.Summary,         SyndicationTextContentKind.Plaintext, true)]     [EntityPropertyMapping("TimeGenerated",         SyndicationItemProperty.Updated,         SyndicationTextContentKind.Plaintext, true)]     [DataServiceKey("EventID")]     public class LogEntry     {         public long EventID         {             get;             set;         }         public string Category         {             get;             set;         }         public string Message         {             get;             set;         }         public DateTime TimeGenerated         {             get;             set;         }         public string Source         {             get;             set;         }     } As you can see, I used the new feature “Friendly feeds” to map several properties in the entries with standard ATOM elements. The “DataServiceKey” is only necessary because I am using the Reflection Provider (the exposed IQueryable implementation is just Linq to Objects) rather than the default Entity Framework Provider. The data service implementation is also quite simple, just a couple of lines were needed to expose the data source created previously. public class LogDataService : DataService<LogDataSource>     {         public static void InitializeService(IDataServiceConfiguration config)         {             config.SetEntitySetAccessRule("*", EntitySetRights.AllRead);         }         protected override LogDataSource CreateDataSource()         {             string source = ConfigurationManager.AppSettings["EventLogSource"];             if (source == null)             {                 throw new ApplicationException("The EventLogSource appsetting is missing in the configuration file");             }             return new LogDataSource(source);         }     } With this implementation in place, the final users not only get a feed with all the latest errors in the event log, but also support for performing queries against that data. This is one of the great things about ADO.NET Data services.

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• Using MAC Authentication for simple Web API’s consumption

  - by cibrax

  For simple scenarios of Web API consumption where identity delegation is not required, traditional http authentication schemas such as basic, certificates or digest are the most used nowadays. All these schemas rely on sending the caller credentials or some representation of it in every request message as part of the Authorization header, so they are prone to suffer phishing attacks if they are not correctly secured at transport level with https. In addition, most client applications typically authenticate two different things, the caller application and the user consuming the API on behalf of that application. For most cases, the schema is simplified by using a single set of username and password for authenticating both, making necessary to store those credentials temporally somewhere in memory. The true is that you can use two different identities, one for the user running the application, which you might authenticate just once during the first call when the application is initialized, and another identity for the application itself that you use on every call. Some cloud vendors like Windows Azure or Amazon Web Services have adopted an schema to authenticate the caller application based on a Message Authentication Code (MAC) generated with a symmetric algorithm using a key known by the two parties, the caller and the Web API. The caller must include a MAC as part of the Authorization header created from different pieces of information in the request message such as the address, the host, and some other headers. The Web API can authenticate the caller by using the key associated to it and validating the attached MAC in the request message. In that way, no credentials are sent as part of the request message, so there is no way an attacker to intercept the message and get access to those credentials. Anyways, this schema also suffers from some deficiencies that can generate attacks. For example, brute force can be still used to infer the key used for generating the MAC, and impersonate the original caller. This can be mitigated by renewing keys in a relative short period of time. This schema as any other can be complemented with transport security. Eran Rammer, one of the brains behind OAuth, has recently published an specification of a protocol based on MAC for Http authentication called Hawk. The initial version of the spec is available here. A curious fact is that the specification per se does not exist, and the specification itself is the code that Eran initially wrote using node.js. In that implementation, you can associate a key to an user, so once the MAC has been verified on the Web API, the user can be inferred from that key. Also a timestamp is used to avoid replay attacks. As a pet project, I decided to port that code to .NET using ASP.NET Web API, which is available also in github under https://github.com/pcibraro/hawknet Enjoy!.

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• Authenticating clients in the new WCF Http stack

  - by cibrax

  About this time last year, I wrote a couple of posts about how to use the “Interceptors” from the REST starker kit for implementing several authentication mechanisms like “SAML”, “Basic Authentication” or “OAuth” in the WCF Web programming model. The things have changed a lot since then, and Glenn finally put on our hands a new version of the Web programming model that deserves some attention and I believe will help us a lot to build more Http oriented services in the .NET stack. What you can get today from wcf.codeplex.com is a preview with some cool features like Http Processors (which I already discussed here), a new and improved version of the HttpClient library, Dependency injection and better TDD support among others. However, the framework still does not support an standard way of doing client authentication on the services (This is something planned for the upcoming releases I believe). For that reason, moving the existing authentication interceptors to this new programming model was one of the things I did in the last few days. In order to make authentication simple and easy to extend,  I first came up with a model based on what I called “Authentication Interceptors”. An authentication interceptor maps to an existing Http authentication mechanism and implements the following interface, public interface IAuthenticationInterceptor{ string Scheme { get; } bool DoAuthentication(HttpRequestMessage request, HttpResponseMessage response, out IPrincipal principal);} An authentication interceptors basically needs to returns the http authentication schema that implements in the property “Scheme”, and implements the authentication mechanism in the method “DoAuthentication”. As you can see, this last method “DoAuthentication” only relies on the HttpRequestMessage and HttpResponseMessage classes, making the testing of this interceptor very simple (There is no need to do some black magic with the WCF context or messages). After this, I implemented a couple of interceptors for supporting basic authentication and brokered authentication with SAML (using WIF) in my services. The following code illustrates how the basic authentication interceptors looks like. public class BasicAuthenticationInterceptor : IAuthenticationInterceptor{ Func<UsernameAndPassword, bool> userValidation; string realm;  public BasicAuthenticationInterceptor(Func<UsernameAndPassword, bool> userValidation, string realm) { if (userValidation == null) throw new ArgumentNullException("userValidation");  if (string.IsNullOrEmpty(realm)) throw new ArgumentNullException("realm");  this.userValidation = userValidation; this.realm = realm; }  public string Scheme { get { return "Basic"; } }  public bool DoAuthentication(HttpRequestMessage request, HttpResponseMessage response, out IPrincipal principal) { string[] credentials = ExtractCredentials(request); if (credentials.Length == 0 || !AuthenticateUser(credentials[0], credentials[1])) { response.StatusCode = HttpStatusCode.Unauthorized; response.Content = new StringContent("Access denied"); response.Headers.WwwAuthenticate.Add(new AuthenticationHeaderValue("Basic", "realm=" + this.realm));  principal = null;  return false; } else { principal = new GenericPrincipal(new GenericIdentity(credentials[0]), new string[] {});  return true; } }  private string[] ExtractCredentials(HttpRequestMessage request) { if (request.Headers.Authorization != null && request.Headers.Authorization.Scheme.StartsWith("Basic")) { string encodedUserPass = request.Headers.Authorization.Parameter.Trim();  Encoding encoding = Encoding.GetEncoding("iso-8859-1"); string userPass = encoding.GetString(Convert.FromBase64String(encodedUserPass)); int separator = userPass.IndexOf(':');  string[] credentials = new string[2]; credentials[0] = userPass.Substring(0, separator); credentials[1] = userPass.Substring(separator + 1);  return credentials; }  return new string[] { }; }  private bool AuthenticateUser(string username, string password) { var usernameAndPassword = new UsernameAndPassword { Username = username, Password = password };  if (this.userValidation(usernameAndPassword)) { return true; }  return false; }} This interceptor receives in the constructor a callback in the form of a Func delegate for authenticating the user and the “realm”, which is required as part of the implementation. The rest is a general implementation of the basic authentication mechanism using standard http request and response messages. I also implemented another interceptor for authenticating a SAML token with WIF. public class SamlAuthenticationInterceptor : IAuthenticationInterceptor{ SecurityTokenHandlerCollection handlers = null;  public SamlAuthenticationInterceptor(SecurityTokenHandlerCollection handlers) { if (handlers == null) throw new ArgumentNullException("handlers");  this.handlers = handlers; }  public string Scheme { get { return "saml"; } }  public bool DoAuthentication(HttpRequestMessage request, HttpResponseMessage response, out IPrincipal principal) { SecurityToken token = ExtractCredentials(request);  if (token != null) { ClaimsIdentityCollection claims = handlers.ValidateToken(token);  principal = new ClaimsPrincipal(claims);  return true; } else { response.StatusCode = HttpStatusCode.Unauthorized; response.Content = new StringContent("Access denied");  principal = null;  return false; } }  private SecurityToken ExtractCredentials(HttpRequestMessage request) { if (request.Headers.Authorization != null && request.Headers.Authorization.Scheme == "saml") { XmlTextReader xmlReader = new XmlTextReader(new StringReader(request.Headers.Authorization.Parameter));  var col = SecurityTokenHandlerCollection.CreateDefaultSecurityTokenHandlerCollection(); SecurityToken token = col.ReadToken(xmlReader);  return token; }  return null; }}This implementation receives a “SecurityTokenHandlerCollection” instance as part of the constructor. This class is part of WIF, and basically represents a collection of token managers to know how to handle specific xml authentication tokens (SAML is one of them). I also created a set of extension methods for injecting these interceptors as part of a service route when the service is initialized. var basicAuthentication = new BasicAuthenticationInterceptor((u) => true, "ContactManager");var samlAuthentication = new SamlAuthenticationInterceptor(serviceConfiguration.SecurityTokenHandlers); // use MEF for providing instancesvar catalog = new AssemblyCatalog(typeof(Global).Assembly);var container = new CompositionContainer(catalog);var configuration = new ContactManagerConfiguration(container); RouteTable.Routes.AddServiceRoute<ContactResource>("contact", configuration, basicAuthentication, samlAuthentication);RouteTable.Routes.AddServiceRoute<ContactsResource>("contacts", configuration, basicAuthentication, samlAuthentication); In the code above, I am injecting the basic authentication and saml authentication interceptors in the “contact” and “contacts” resource implementations that come as samples in the code preview. I will use another post to discuss more in detail how the brokered authentication with SAML model works with this new WCF Http bits. The code is available to download in this location.

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• Workarounds for supporting MVVM in the Silverlight TreeView Control

  - by cibrax

  MVVM (Model-View-ViewModel) is the pattern that you will typically choose for building testable user interfaces either in WPF or Silverlight. This pattern basically relies on the data binding support in those two technologies for mapping an existing model class (the view model) to the different parts of the UI or view. Unfortunately, MVVM was not threated as first citizen for some of controls released out of the box in the Silverlight runtime or the Silverlight toolkit. That means that using data binding for implementing MVVM is not always something trivial and usually requires some customization in the existing controls. In ran into different problems myself trying to fully support data binding in controls like the tree view or the context menu or things like drag & drop.  For that reason, I decided to write this post to show how the tree view control or the tree view items can be customized to support data binding in many of its properties. In first place, you will typically use a tree view for showing hierarchical data so the view model somehow must reflect that hierarchy. An easy way to implement hierarchy in a model is to use a base item element like this one, public abstract class TreeItemModel { public abstract IEnumerable<TreeItemModel> Children; } You can later derive your concrete model classes from that base class. For example, public class CustomerModel { public string FullName { get; set; } public string Address { get; set; } public IEnumerable<OrderModel> Orders { get; set; } }   public class CustomerTreeItemModel : TreeItemModel { public CustomerTreeItemModel(CustomerModel customer) { }   public override IEnumerable<TreeItemModel> Children { get { // Return orders } } } The Children property in the CustomerTreeItem model implementation can return for instance an ObservableCollection<TreeItemModel> with the orders, so the tree view will automatically subscribe to all the changes in the collection. You can bind this model to the tree view control in the UI by using a Hierarchical data template. <e:TreeView x:Name="TreeView" ItemsSource="{Binding Customers}"> <e:TreeView.ItemTemplate> <sdk:HierarchicalDataTemplate ItemsSource="{Binding Children}"> <!-- TEMPLATE --> </sdk:HierarchicalDataTemplate> </e:TreeView.ItemTemplate> </e:TreeView> An interesting behavior with the Children property and the Hierarchical data template is that the Children property is only invoked before the expansion, so you can use lazy load at this point (The tree view control will not expand the whole tree in the first expansion). The problem with using MVVM in this control is that you can not bind properties in model with specific properties of the TreeView item such as IsSelected or IsExpanded. Here is where you need to customize the existing tree view control to support data binding in tree items. public class CustomTreeView : TreeView { public CustomTreeView() { }   protected override DependencyObject GetContainerForItemOverride() { CustomTreeViewItem tvi = new CustomTreeViewItem(); Binding expandedBinding = new Binding("IsExpanded"); expandedBinding.Mode = BindingMode.TwoWay; tvi.SetBinding(CustomTreeViewItem.IsExpandedProperty, expandedBinding); Binding selectedBinding = new Binding("IsSelected"); selectedBinding.Mode = BindingMode.TwoWay; tvi.SetBinding(CustomTreeViewItem.IsSelectedProperty, selectedBinding); return tvi; } }   public class CustomTreeViewItem : TreeViewItem { public CustomTreeViewItem() { }   protected override DependencyObject GetContainerForItemOverride() { CustomTreeViewItem tvi = new CustomTreeViewItem(); Binding expandedBinding = new Binding("IsExpanded"); expandedBinding.Mode = BindingMode.TwoWay; tvi.SetBinding(CustomTreeViewItem.IsExpandedProperty, expandedBinding); Binding selectedBinding = new Binding("IsSelected"); selectedBinding.Mode = BindingMode.TwoWay; tvi.SetBinding(CustomTreeViewItem.IsSelectedProperty, selectedBinding); return tvi; } } You basically need to derive the TreeView and TreeViewItem controls to manually add a binding for the properties you need. In the example above, I am adding a binding for the “IsExpanded” and “IsSelected” properties in the items. The model for the tree items now needs to be extended to support those properties as well, public abstract class TreeItemModel : INotifyPropertyChanged { bool isExpanded = false; bool isSelected = false;   public abstract IEnumerable<TreeItemModel> Children { get; }   public bool IsExpanded { get { return isExpanded; } set { isExpanded = value; if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("IsExpanded")); } }   public bool IsSelected { get { return isSelected; } set { isSelected = value; if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("IsSelected")); } }   public event PropertyChangedEventHandler PropertyChanged; } However, as soon as you use this custom tree view control, you lose all the automatic styles from the built-in toolkit themes because they are tied to the control type (TreeView in this case).  The only ugly workaround I found so far for this problem is to copy the styles from the Toolkit source code and reuse them in the application.

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• Enabling Service Availability in WCF Services

  - by cibrax

  It is very important for the enterprise to know which services are operational at any given point. There are many factors that can affect the availability of the services, some of them are external like a database not responding or any dependant service not working. However, in some cases, you only want to know whether a service is up or down, so a simple heart-beat mechanism with “Ping” messages would do the trick. Unfortunately, WCF does not provide a built-in mechanism to support this functionality, and you probably don’t to implement a “Ping” operation in any service that you have out there. For solving this in a generic way, there is a WCF extensibility point that comes to help us, the “Operation Invokers”. In a nutshell, an operation invoker is the class responsible invoking the service method with a set of parameters and generate the output parameters with the return value. What I am going to do here is to implement a custom operation invoker that intercepts any call to the service, and detects whether a “Ping” header was attached to the message. If the “Ping” header is detected, the operation invoker returns a new header to tell the client that the service is alive, and the real operation execution is omitted. In that way, we have a simple heart beat mechanism based on the messages that include a "Ping” header, so the client application can determine at any point whether the service is up or down. My operation invoker wraps the default implementation attached by default to any operation by WCF. internal class PingOperationInvoker : IOperationInvoker { IOperationInvoker innerInvoker; object[] outputs = null; object returnValue = null; public const string PingHeaderName = "Ping"; public const string PingHeaderNamespace = "http://tellago.serviceModel"; public PingOperationInvoker(IOperationInvoker innerInvoker, OperationDescription description) { this.innerInvoker = innerInvoker; outputs = description.SyncMethod.GetParameters() .Where(p => p.IsOut) .Select(p => DefaultForType(p.ParameterType)).ToArray(); var returnValue = DefaultForType(description.SyncMethod.ReturnType); } private static object DefaultForType(Type targetType) { return targetType.IsValueType ? Activator.CreateInstance(targetType) : null; } public object Invoke(object instance, object[] inputs, out object[] outputs) { object returnValue; if (Invoke(out returnValue, out outputs)) { return returnValue; } else { return this.innerInvoker.Invoke(instance, inputs, out outputs); } } private bool Invoke(out object returnValue, out object[] outputs) { object untypedProperty = null; if (OperationContext.Current .IncomingMessageProperties.TryGetValue(HttpRequestMessageProperty.Name, out untypedProperty)) { var httpRequestProperty = untypedProperty as HttpRequestMessageProperty; if (httpRequestProperty != null) { if (httpRequestProperty.Headers[PingHeaderName] != null) { outputs = this.outputs; if (OperationContext.Current .IncomingMessageProperties.TryGetValue(HttpRequestMessageProperty.Name, out untypedProperty)) { var httpResponseProperty = untypedProperty as HttpResponseMessageProperty; httpResponseProperty.Headers.Add(PingHeaderName, "Ok"); } returnValue = this.returnValue; return true; } } } var headers = OperationContext.Current.IncomingMessageHeaders; if (headers.FindHeader(PingHeaderName, PingHeaderNamespace) > -1) { outputs = this.outputs; MessageHeader<string> header = new MessageHeader<string>("Ok"); var untyped = header.GetUntypedHeader(PingHeaderName, PingHeaderNamespace); OperationContext.Current.OutgoingMessageHeaders.Add(untyped); returnValue = this.returnValue; return true; } returnValue = null; outputs = null; return false; } } The implementation above looks for the “Ping” header either in the Http Request or the Soap message. The next step is to implement a behavior for attaching this operation invoker to the services we want to monitor. [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, AllowMultiple = false, Inherited = true)] public class PingBehavior : Attribute, IServiceBehavior, IOperationBehavior { public void AddBindingParameters(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints, BindingParameterCollection bindingParameters) { } public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) { } public void Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) { foreach (var endpoint in serviceDescription.Endpoints) { foreach (var operation in endpoint.Contract.Operations) { if (operation.Behaviors.Find<PingBehavior>() == null) operation.Behaviors.Add(this); } } } public void AddBindingParameters(OperationDescription operationDescription, BindingParameterCollection bindingParameters) { } public void ApplyClientBehavior(OperationDescription operationDescription, ClientOperation clientOperation) { } public void ApplyDispatchBehavior(OperationDescription operationDescription, DispatchOperation dispatchOperation) { dispatchOperation.Invoker = new PingOperationInvoker(dispatchOperation.Invoker, operationDescription); } public void Validate(OperationDescription operationDescription) { } } As an operation invoker can only be added in an “operation behavior”, a trick I learned in the past is that you can implement a service behavior as well and use the “Validate” method to inject it in all the operations, so the final configuration is much easier and cleaner. You only need to decorate the service with a simple attribute to enable the “Ping” functionality. [PingBehavior] public class HelloWorldService : IHelloWorld { public string Hello(string name) { return "Hello " + name; } } On the other hand, the client application needs to send a dummy message with a “Ping” header to detect whether the service is available or not. In order to simplify this task, I created a extension method in the WCF client channel to do this work. public static class ClientChannelExtensions { const string PingNamespace = "http://tellago.serviceModel"; const string PingName = "Ping"; public static bool IsAvailable<TChannel>(this IClientChannel channel, Action<TChannel> operation) { try { using (OperationContextScope scope = new OperationContextScope(channel)) { MessageHeader<string> header = new MessageHeader<string>(PingName); var untyped = header.GetUntypedHeader(PingName, PingNamespace); OperationContext.Current.OutgoingMessageHeaders.Add(untyped); try { operation((TChannel)channel); var headers = OperationContext.Current.IncomingMessageHeaders; if (headers.Any(h => h.Name == PingName && h.Namespace == PingNamespace)) { return true; } else { return false; } } catch (CommunicationException) { return false; } } } catch (Exception) { return false; } } } This extension method basically adds a “Ping” header to the request message, executes the operation passed as argument (Action<TChannel> operation), and looks for the corresponding “Ping” header in the response to see the results. The client application can use this extension with a single line of code, var client = new ServiceReference.HelloWorldClient(); var isAvailable = client.InnerChannel.IsAvailable<IHelloWorld>((c) => c.Hello(null)); The “isAvailable” variable will tell the client application whether the service is available or not. You can download the complete implementation from this location.    

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• Professional WCF 4.0: Windows Communication Foundation with .NET 4.0

  - by cibrax

  The book in which I been working on since last year finally went to the light this week. It has been the result of hard work between me and three other Connected Systems MVP, my friend Fabio Cozzolino, Kurt Claeys and Johann Grabner. If you are interested in learning the new features in WCF 4.0, but also WCF in general and how to apply in real world scenarios, this book is for you. I dedicated three chapters of this book to one of my favorites topics, Security, from the basics to more complicated scenarios with Claim-Based security and Federated authentication using WCF services with Windows Identity Foundation. You can find more information about the book and the table of contents in the Wrox web site here.

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• Doing unit and integration tests with the Web API HttpClient

  - by cibrax

  One of the nice things about the new HttpClient in System.Net.Http is the support for mocking responses or handling requests in a http server hosted in-memory. While the first option is useful for scenarios in which we want to test our client code in isolation (unit tests for example), the second one enables more complete integration testing scenarios that could include some more components in the stack such as model binders or message handlers for example.   The HttpClient can receive a HttpMessageHandler as argument in one of its constructors. public class HttpClient : HttpMessageInvoker { public HttpClient(); public HttpClient(HttpMessageHandler handler); public HttpClient(HttpMessageHandler handler, bool disposeHandler); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } For the first scenario, you can create a new HttpMessageHandler that fakes the response, which you can use in your unit test. The only requirement is that you somehow inject an HttpClient with this custom handler in the client code. public class FakeHttpMessageHandler : HttpMessageHandler { HttpResponseMessage response; public FakeHttpMessageHandler(HttpResponseMessage response) { this.response = response; } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } In an unit test, you can do something like this. var fakeResponse = new HttpResponse(); var fakeHandler = new FakeHttpMessageHandler(fakeResponse); var httpClient = new HttpClient(fakeHandler); var customerService = new CustomerService(httpClient); // Do something // Asserts .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } CustomerService in this case is the class under test, and the one that receives an HttpClient initialized with our fake handler. For the second scenario in integration tests, there is a In-Memory host “System.Web.Http.HttpServer” that also derives from HttpMessageHandler and you can use with a HttpClient instance in your test. This has been discussed already in these two great posts from Pedro and Filip. 

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• Making your WCF Web Apis to speak in multiple languages

  - by cibrax

  One of the key aspects of how the web works today is content negotiation. The idea of content negotiation is based on the fact that a single resource can have multiple representations, so user agents (or clients) and servers can work together to chose one of them. The http specification defines several “Accept” headers that a client can use to negotiate content with a server, and among all those, there is one for restricting the set of natural languages that are preferred as a response to a request, “Accept-Language”. For example, a client can specify “es” in this header for specifying that he prefers to receive the content in spanish or “en” in english. However, there are certain scenarios where the “Accept-Language” header is just not enough, and you might want to have a way to pass the “accepted” language as part of the resource url as an extension. For example, http://localhost/ProductCatalog/Products/1.es” returns all the descriptions for the product with id “1” in spanish. This is useful for scenarios in which you want to embed the link somewhere, such a document, an email or a page.  Supporting both scenarios, the header and the url extension, is really simple in the new WCF programming model. You only need to provide a processor implementation for any of them. Let’s say I have a resource implementation as part of a product catalog I want to expose with the WCF web apis. [ServiceContract][Export]public class ProductResource{ IProductRepository repository;  [ImportingConstructor] public ProductResource(IProductRepository repository) { this.repository = repository; }  [WebGet(UriTemplate = "{id}")] public Product Get(string id, HttpResponseMessage response) { var product = repository.GetById(int.Parse(id)); if (product == null) { response.StatusCode = HttpStatusCode.NotFound; response.Content = new StringContent(Messages.OrderNotFound); }  return product; }} The Get method implementation in this resource assumes the desired culture will be attached to the current thread (Thread.CurrentThread.Culture). Another option is to pass the desired culture as an additional argument in the method, so my processor implementation will handle both options. This method is also using an auto-generated class for handling string resources, Messages, which is available in the different cultures that the service implementation supports. For example, Messages.resx contains “OrderNotFound”: “Order Not Found” Messages.es.resx contains “OrderNotFound”: “No se encontro orden” The processor implementation bellow tackles the first scenario, in which the desired language is passed as part of the “Accept-Language” header. public class CultureProcessor : Processor<HttpRequestMessage, CultureInfo>{ string defaultLanguage = null;  public CultureProcessor(string defaultLanguage = "en") { this.defaultLanguage = defaultLanguage; this.InArguments[0].Name = HttpPipelineFormatter.ArgumentHttpRequestMessage; this.OutArguments[0].Name = "culture"; }  public override ProcessorResult<CultureInfo> OnExecute(HttpRequestMessage request) { CultureInfo culture = null; if (request.Headers.AcceptLanguage.Count > 0) { var language = request.Headers.AcceptLanguage.First().Value; culture = new CultureInfo(language); } else { culture = new CultureInfo(defaultLanguage); }  Thread.CurrentThread.CurrentCulture = culture; Messages.Culture = culture;  return new ProcessorResult<CultureInfo> { Output = culture }; }}   As you can see, the processor initializes a new CultureInfo instance with the value provided in the “Accept-Language” header, and set that instance to the current thread and the auto-generated resource class with all the messages. In addition, the CultureInfo instance is returned as an output argument called “culture”, making possible to receive that argument in any method implementation   The following code shows the implementation of the processor for handling languages as url extensions.   public class CultureExtensionProcessor : Processor<HttpRequestMessage, Uri>{ public CultureExtensionProcessor() { this.OutArguments[0].Name = HttpPipelineFormatter.ArgumentUri; }  public override ProcessorResult<Uri> OnExecute(HttpRequestMessage httpRequestMessage) { var requestUri = httpRequestMessage.RequestUri.OriginalString;  var extensionPosition = requestUri.LastIndexOf(".");  if (extensionPosition > -1) { var extension = requestUri.Substring(extensionPosition + 1);  var query = httpRequestMessage.RequestUri.Query;  requestUri = string.Format("{0}?{1}", requestUri.Substring(0, extensionPosition), query); ;  var uri = new Uri(requestUri);  httpRequestMessage.Headers.AcceptLanguage.Clear();  httpRequestMessage.Headers.AcceptLanguage.Add(new StringWithQualityHeaderValue(extension));  var result = new ProcessorResult<Uri>();  result.Output = uri;  return result; }  return new ProcessorResult<Uri>(); }} The last step is to inject both processors as part of the service configuration as it is shown bellow, public void RegisterRequestProcessorsForOperation(HttpOperationDescription operation, IList<Processor> processors, MediaTypeProcessorMode mode){ processors.Insert(0, new CultureExtensionProcessor()); processors.Add(new CultureProcessor());} Once you configured the two processors in the pipeline, your service will start speaking different languages :). Note: Url extensions don’t seem to be working in the current bits when you are using Url extensions in a base address. As far as I could see, ASP.NET intercepts the request first and tries to route the request to a registered ASP.NET Http Handler with that extension. For example, “http://localhost/ProductCatalog/products.es” does not work, but “http://localhost/ProductCatalog/products/1.es” does.

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• Monitoring your WCF Web Apis with AppFabric

  - by cibrax

  The other day, Ron Jacobs made public a template in the Visual Studio Gallery for enabling monitoring capabilities to any existing WCF Http service hosted in Windows AppFabric. I thought it would be a cool idea to reuse some of that for doing the same thing on the new WCF Web Http stack. Windows AppFabric provides a dashboard that you can use to dig into some metrics about the services usage, such as number of calls, errors or information about different events during a service call. Those events not only include information about the WCF pipeline, but also custom events that any developer can inject and make sense for troubleshooting issues.      This monitoring capabilities can be enabled on any specific IIS virtual directory by using the AppFabric configuration tool or adding the following configuration sections to your existing web app, <system.serviceModel> <serviceHostingEnvironment aspNetCompatibilityEnabled="true" multipleSiteBindingsEnabled="true" /> <diagnostics etwProviderId="3e99c707-3503-4f33-a62d-2289dfa40d41"> <endToEndTracing propagateActivity="true" messageFlowTracing="true" /> </diagnostics> <behaviors> <serviceBehaviors> <behavior name=""> <etwTracking profileName="EndToEndMonitoring Tracking Profile" /> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel>   <microsoft.applicationServer> <monitoring> <default enabled="true" connectionStringName="ApplicationServerMonitoringConnectionString" monitoringLevel="EndToEndMonitoring" /> </monitoring> </microsoft.applicationServer> Bad news is that none of the configuration above can be easily set on code by using the new configuration model for WCF Web stack.  A good thing is that you easily disable it in the configuration when you no longer need it, and also uses ETW, a general-purpose and high-speed tracing facility provided by the operating system (it’s part of the windows kernel). By adding that configuration section, AppFabric will start monitoring your service automatically and providing some basic event information about the service calls. You need some custom code for injecting custom events in the monitoring data. What I did here is to copy and refactor the “WCFUserEventProvider” class provided as sample in the Ron’s template to make it more TDD friendly when using IoC. I created a simple interface “ILogger” that any service (or resource) can use to inject custom events or monitoring information in the AppFabric database. public interface ILogger { bool WriteError(string name, string format, params object[] args); bool WriteWarning(string name, string format, params object[] args); bool WriteInformation(string name, string format, params object[] args); } The “WCFUserEventProvider” class implements this interface by making possible to send the events to the AppFabric monitoring database. The service or resource implementation can receive an “ILogger” as part of the constructor. [ServiceContract] [Export] public class OrderResource { IOrderRepository repository; ILogger logger;   [ImportingConstructor] public OrderResource(IOrderRepository repository, ILogger logger) { this.repository = repository; this.logger = logger; }   [WebGet(UriTemplate = "{id}")] public Order Get(string id, HttpResponseMessage response) { var order = this.repository.All.FirstOrDefault(o => o.OrderId == int.Parse(id, CultureInfo.InvariantCulture)); if (order == null) { response.StatusCode = HttpStatusCode.NotFound; response.Content = new StringContent("Order not found"); }   this.logger.WriteInformation("Order Requested", "Order Id {0}", id);   return order; } } The example above uses “MEF” as IoC for injecting a repository and the logger implementation into the service. You can also see how the logger is used to write an information event in the monitoring database. The following image illustrates how the custom event is injected and the information becomes available for any user in the dashboard. An issue that you might run into and I hope the WCF and AppFabric teams fixed soon is that any WCF service that uses friendly URLs with ASP.NET routing does not get listed as a available service in the WCF services tab in the AppFabric console. The complete example is available to download from here.

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• Unit testing ASP.NET Web API controllers that rely on the UrlHelper

  - by cibrax

  UrlHelper is the class you can use in ASP.NET Web API to automatically infer links from the routing table without hardcoding anything. For example, the following code uses the helper to infer the location url for a new resource,public HttpResponseMessage Post(User model) { var response = Request.CreateResponse(HttpStatusCode.Created, user); var link = Url.Link("DefaultApi", new { id = id, controller = "Users" }); response.Headers.Location = new Uri(link); return response; } That code uses a previously defined route “DefaultApi”, which you might configure in the HttpConfiguration object (This is the route generated by default when you create a new Web API project). The problem with UrlHelper is that it requires from some initialization code before you can invoking it from a unit test (for testing the Post method in this example). If you don’t initialize the HttpConfiguration and Request instances associated to the controller from the unit test, it will fail miserably. After digging into the ASP.NET Web API source code a little bit, I could figure out what the requirements for using the UrlHelper are. It relies on the routing table configuration, and a few properties you need to add to the HttpRequestMessage. The following code illustrates what’s needed,var controller = new UserController(); controller.Configuration = new HttpConfiguration(); var route = controller.Configuration.Routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional } ); var routeData = new HttpRouteData(route, new HttpRouteValueDictionary { { "id", "1" }, { "controller", "Users" } } ); controller.Request = new HttpRequestMessage(HttpMethod.Post, "http://localhost:9091/"); controller.Request.Properties.Add(HttpPropertyKeys.HttpConfigurationKey, controller.Configuration); controller.Request.Properties.Add(HttpPropertyKeys.HttpRouteDataKey, routeData);  The HttpRouteData instance should be initialized with the route values you will use in the controller method (“id” and “controller” in this example). Once you have correctly setup all those properties, you shouldn’t have any problem to use the UrlHelper. There is no need to mock anything else. Enjoy!!.

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• Implementing synchronous MediaTypeFormatters in ASP.NET Web API

  - by cibrax

  One of main characteristics of MediaTypeFormatter’s in ASP.NET Web API is that they leverage the Task Parallel Library (TPL) for reading or writing an model into an stream. When you derive your class from the base class MediaTypeFormatter, you have to either implement the WriteToStreamAsync or ReadFromStreamAsync methods for writing or reading a model from a stream respectively. These two methods return a Task, which internally does all the serialization work, as it is illustrated bellow. public abstract class MediaTypeFormatter { public virtual Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content, TransportContext transportContext); public virtual Task<object> ReadFromStreamAsync(Type type, Stream readStream, HttpContent content, IFormatterLogger formatterLogger); }   .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } However, most of the times, serialization is a safe operation that can be done synchronously. In fact, many of the serializer classes you will find in the .NET framework only provide sync methods. So the question is, how you can transform that synchronous work into a Task ?. Creating a new task using the method Task.Factory.StartNew for doing all the serialization work would be probably the typical answer. That would work, as a new task is going to be scheduled. However, that might involve some unnecessary context switches, which are out of our control and might be affect performance on server code specially.   If you take a look at the source code of the MediaTypeFormatters shipped as part of the framework, you will notice that they actually using another pattern, which uses a TaskCompletionSource class. public Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content, TransportContext transportContext) {   var tsc = new TaskCompletionSource<AsyncVoid>(); tsc.SetResult(default(AsyncVoid));   //Do all the serialization work here synchronously   return tsc.Task; }   /// <summary> /// Used as the T in a "conversion" of a Task into a Task{T} /// </summary> private struct AsyncVoid { } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } They are basically doing all the serialization work synchronously and using a TaskCompletionSource for returning a task already done. To conclude this post, this is another approach you might want to consider when using serializers that are not compatible with an async model. Update: Henrik Nielsen from the ASP.NET team pointed out the existence of a built-in media type formatter for writing sync formatters. BufferedMediaTypeFormatter http://t.co/FxOfeI5x

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• Consuming the Amazon S3 service from a Win8 Metro Application

  - by cibrax

  As many of the existing Http APIs for Cloud Services, AWS also provides a set of different platform SDKs for hiding many of complexities present in the APIs. While there is a platform SDK for .NET, which is open source and available in C#, that SDK does not work in Win8 Metro Applications for the changes introduced in WinRT. WinRT offers a complete different set of APIs for doing I/O operations such as doing http calls or using cryptography for signing or encrypting data, two aspects that are absolutely necessary for consuming AWS. All the I/O APIs available as part of WinRT are asynchronous, and uses the TPL model for .NET applications (HTML and JavaScript Metro applications use a model based in promises, which is similar concept).  In the case of S3, the http Authorization header is used for two purposes, authenticating clients and make sure the messages were not altered while they were in transit. For doing that, it uses a signature or hash of the message content and some of the headers using a symmetric key (That's just one of the available mechanisms). Windows Azure for example also uses the same mechanism in many of its APIs. There are three challenges that any developer working for first time in Metro will have to face to consume S3, the new WinRT APIs, the asynchronous nature of them and the complexity introduced for generating the Authorization header. Having said that, I decided to write this post with some of the gotchas I found myself trying to consume this Amazon service. 1. Generating the signature for the Authorization header All the cryptography APIs in WinRT are available under Windows.Security.Cryptography namespace. Many of operations available in these APIs uses the concept of buffers (IBuffer) for representing a chunk of binary data. As you will see in the example below, these buffers are mainly generated with the use of static methods in a WinRT class CryptographicBuffer available as part of the namespace previously mentioned. private string DeriveAuthToken(string resource, string httpMethod, string timestamp) { var stringToSign = string.Format("{0}\n" + "\n" + "\n" + "\n" + "x-amz-date:{1}\n" + "/{2}/", httpMethod, timestamp, resource); var algorithm = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1"); var keyMaterial = CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(this.secret)); var hmacKey = algorithm.CreateKey(keyMaterial); var signature = CryptographicEngine.Sign( hmacKey, CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(stringToSign)) ); return CryptographicBuffer.EncodeToBase64String(signature); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The algorithm that determines the information or content you need to use for generating the signature is very well described as part of the AWS documentation. In this case, this method is generating a signature required for creating a new bucket. A HmacSha1 hash is computed using a secret or symetric key provided by AWS in the management console. 2. Sending an Http Request to the S3 service WinRT also ships with the System.Net.Http.HttpClient that was first introduced some months ago with ASP.NET Web API. This client provides a rich interface on top the traditional WebHttpRequest class, and also solves some of limitations found in this last one. There are a few things that don't work with a raw WebHttpRequest such as setting the Host header, which is something absolutely required for consuming S3. Also, HttpClient is more friendly for doing unit tests, as it receives a HttpMessageHandler as part of the constructor that can fake to emulate a real http call. This is how the code for consuming the service with HttpClient looks like, public async Task<S3Response> CreateBucket(string name, string region = null, params string[] acl) { var timestamp = string.Format("{0:r}", DateTime.UtcNow); var auth = DeriveAuthToken(name, "PUT", timestamp); var request = new HttpRequestMessage(HttpMethod.Put, "http://s3.amazonaws.com/"); request.Headers.Host = string.Format("{0}.s3.amazonaws.com", name); request.Headers.TryAddWithoutValidation("Authorization", "AWS " + this.key + ":" + auth); request.Headers.Add("x-amz-date", timestamp); var client = new HttpClient(); var response = await client.SendAsync(request); return new S3Response { Succeed = response.StatusCode == HttpStatusCode.OK, Message = (response.Content != null) ? await response.Content.ReadAsStringAsync() : null }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You will notice a few additional things in this code. By default, HttpClient validates the values for some well-know headers, and Authorization is one of them. It won't allow you to set a value with ":" on it, which is something that S3 expects. However, that's not a problem at all, as you can skip the validation by using the TryAddWithoutValidation method. Also, the code is heavily relying on the new async and await keywords to transform all the asynchronous calls into synchronous ones. In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, public class FakeHttpMessageHandler : HttpMessageHandler { HttpResponseMessage response; public FakeHttpMessageHandler(HttpResponseMessage response) { this.response = response; } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can use this handler for injecting any response while you are unit testing the code.

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• Consuming the Amazon S3 service from a Win8 Metro Application

  - by cibrax

  As many of the existing Http APIs for Cloud Services, AWS also provides a set of different platform SDKs for hiding many of complexities present in the APIs. While there is a platform SDK for .NET, which is open source and available in C#, that SDK does not work in Win8 Metro Applications for the changes introduced in WinRT. WinRT offers a complete different set of APIs for doing I/O operations such as doing http calls or using cryptography for signing or encrypting data, two aspects that are absolutely necessary for consuming AWS. All the I/O APIs available as part of WinRT are asynchronous, and uses the TPL model for .NET applications (HTML and JavaScript Metro applications use a model based in promises, which is similar concept).  In the case of S3, the http Authorization header is used for two purposes, authenticating clients and make sure the messages were not altered while they were in transit. For doing that, it uses a signature or hash of the message content and some of the headers using a symmetric key (That's just one of the available mechanisms). Windows Azure for example also uses the same mechanism in many of its APIs. There are three challenges that any developer working for first time in Metro will have to face to consume S3, the new WinRT APIs, the asynchronous nature of them and the complexity introduced for generating the Authorization header. Having said that, I decided to write this post with some of the gotchas I found myself trying to consume this Amazon service. 1. Generating the signature for the Authorization header All the cryptography APIs in WinRT are available under Windows.Security.Cryptography namespace. Many of operations available in these APIs uses the concept of buffers (IBuffer) for representing a chunk of binary data. As you will see in the example below, these buffers are mainly generated with the use of static methods in a WinRT class CryptographicBuffer available as part of the namespace previously mentioned. private string DeriveAuthToken(string resource, string httpMethod, string timestamp) { var stringToSign = string.Format("{0}\n" + "\n" + "\n" + "\n" + "x-amz-date:{1}\n" + "/{2}/", httpMethod, timestamp, resource); var algorithm = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1"); var keyMaterial = CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(this.secret)); var hmacKey = algorithm.CreateKey(keyMaterial); var signature = CryptographicEngine.Sign( hmacKey, CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(stringToSign)) ); return CryptographicBuffer.EncodeToBase64String(signature); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The algorithm that determines the information or content you need to use for generating the signature is very well described as part of the AWS documentation. In this case, this method is generating a signature required for creating a new bucket. A HmacSha1 hash is computed using a secret or symetric key provided by AWS in the management console. 2. Sending an Http Request to the S3 service WinRT also ships with the System.Net.Http.HttpClient that was first introduced some months ago with ASP.NET Web API. This client provides a rich interface on top the traditional WebHttpRequest class, and also solves some of limitations found in this last one. There are a few things that don't work with a raw WebHttpRequest such as setting the Host header, which is something absolutely required for consuming S3. Also, HttpClient is more friendly for doing unit tests, as it receives a HttpMessageHandler as part of the constructor that can fake to emulate a real http call. This is how the code for consuming the service with HttpClient looks like, public async Task<S3Response> CreateBucket(string name, string region = null, params string[] acl) { var timestamp = string.Format("{0:r}", DateTime.UtcNow); var auth = DeriveAuthToken(name, "PUT", timestamp); var request = new HttpRequestMessage(HttpMethod.Put, "http://s3.amazonaws.com/"); request.Headers.Host = string.Format("{0}.s3.amazonaws.com", name); request.Headers.TryAddWithoutValidation("Authorization", "AWS " + this.key + ":" + auth); request.Headers.Add("x-amz-date", timestamp); var client = new HttpClient(); var response = await client.SendAsync(request); return new S3Response { Succeed = response.StatusCode == HttpStatusCode.OK, Message = (response.Content != null) ? await response.Content.ReadAsStringAsync() : null }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You will notice a few additional things in this code. By default, HttpClient validates the values for some well-know headers, and Authorization is one of them. It won't allow you to set a value with ":" on it, which is something that S3 expects. However, that's not a problem at all, as you can skip the validation by using the TryAddWithoutValidation method. Also, the code is heavily relying on the new async and await keywords to transform all the asynchronous calls into synchronous ones. In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, public class FakeHttpMessageHandler : HttpMessageHandler { HttpResponseMessage response; public FakeHttpMessageHandler(HttpResponseMessage response) { this.response = response; } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can use this handler for injecting any response while you are unit testing the code.

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• Debugging Node.js applications for Windows Azure

  - by cibrax

  In case you are developing a new web application with Node.js for Windows Azure, you might notice there is no easy way to debug the application unless you are developing in an integrated IDE like Cloud9. For those that develop applications locally using a text editor (or WebMatrix) and Windows Azure Powershell for Node.js, it requires some steps not documented anywhere for the moment. I spent a few hours on this the other day I practically got nowhere until I received some help from Tomek and the rest of them. The IISNode version that currently ships with the Windows Azure for Node.js SDK does not support debugging by default, so you need to install the IISNode full version available in the github repository.  Once you have installed the full version, you need to enable debugging for the web application by modifying the web.config file <iisnode debuggingEnabled="true" loggingEnabled="true" devErrorsEnabled="true" /> The xml above needs to be inserted within the existing “<system.webServer/>” section. The last step is to open a WebKit browser (e.g. Chrome) and navigate to the URL where your application is hosted but adding the segment “/debug” to  the end. The full URL to the node.js application must be used, for example, http://localhost:81/myserver.js/debug That should open a new instance of Node inspector on the browser, so you can debug the application from there. Enjoy!!

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• Authenticating your windows domain users in the cloud

  - by cibrax

  Moving to the cloud can represent a big challenge for many organizations when it comes to reusing existing infrastructure. For applications that drive existing business processes in the organization, reusing IT assets like active directory represent good part of that challenge. For example, a new web mobile application that sales representatives can use for interacting with an existing CRM system in the organization. In the case of Windows Azure, the Access Control Service (ACS) already provides some integration with ADFS through WS-Federation. That means any organization can create a new trust relationship between the STS running in the ACS and the STS running in ADFS. As the following image illustrates, the ADFS running in the organization should be somehow exposed out of network boundaries to talk to the ACS. This is usually accomplish through an ADFS proxy running in a DMZ. This is the official story for authenticating existing domain users with the ACS.  Getting an ADFS up and running in the organization, which talks to a proxy and also trust the ACS could represent a painful experience. It basically requires  advance knowledge of ADSF and exhaustive testing to get everything right.  However, if you want to get an infrastructure ready for authenticating your domain users in the cloud in a matter of minutes, you will probably want to take a look at the sample I wrote for talking to an existing Active Directory using a regular WCF service through the Service Bus Relay Binding. You can use the WCF ability for self hosting the authentication service within a any program running in the domain (a Windows service typically). The service will not require opening any port as it is opening an outbound connection to the cloud through the Relay Service. In addition, the service will be protected from being invoked by any unauthorized party with the ACS, which will act as a firewall between any client and the service. In that way, we can get a very safe solution up and running almost immediately. To make the solution even more convenient, I implemented an STS in the cloud that internally invokes the service running on premises for authenticating the users. Any existing web application in the cloud can just establish a trust relationship with this STS, and authenticate the users via WS-Federation passive profile with regular http calls, which makes this very attractive for web mobile for example. This is how the WCF service running on premises looks like, [ServiceBehavior(Namespace = "http://agilesight.com/active_directory/agent")] public class ProxyService : IAuthenticationService { IUserFinder userFinder; IUserAuthenticator userAuthenticator;   public ProxyService() : this(new UserFinder(), new UserAuthenticator()) { }   public ProxyService(IUserFinder userFinder, IUserAuthenticator userAuthenticator) { this.userFinder = userFinder; this.userAuthenticator = userAuthenticator; }   public AuthenticationResponse Authenticate(AuthenticationRequest request) { if (userAuthenticator.Authenticate(request.Username, request.Password)) { return new AuthenticationResponse { Result = true, Attributes = this.userFinder.GetAttributes(request.Username) }; }   return new AuthenticationResponse { Result = false }; } } Two external dependencies are used by this service for authenticating users (IUserAuthenticator) and for retrieving user attributes from the user’s directory (IUserFinder). The UserAuthenticator implementation is just a wrapper around the LogonUser Win Api. The UserFinder implementation relies on Directory Services in .NET for searching the user attributes in an existing directory service like Active Directory or the local user store. public UserAttribute[] GetAttributes(string username) { var attributes = new List<UserAttribute>();   var identity = UserPrincipal.FindByIdentity(new PrincipalContext(this.contextType, this.server, this.container), IdentityType.SamAccountName, username); if (identity != null) { var groups = identity.GetGroups(); foreach(var group in groups) { attributes.Add(new UserAttribute { Name = "Group", Value = group.Name }); } if(!string.IsNullOrEmpty(identity.DisplayName)) attributes.Add(new UserAttribute { Name = "DisplayName", Value = identity.DisplayName }); if(!string.IsNullOrEmpty(identity.EmailAddress)) attributes.Add(new UserAttribute { Name = "EmailAddress", Value = identity.EmailAddress }); }   return attributes.ToArray(); } As you can see, the code is simple and uses all the existing infrastructure in Azure to simplify a problem that looks very complex at first glance with ADFS. All the source code for this sample is available to download (or change) in this GitHub repository, https://github.com/AgileSight/ActiveDirectoryForCloud

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• Telesharp – An Application Repository for .NET applications

  - by cibrax

  A year ago, we released SO-Aware as our first product in Tellago Studios. SO-Aware represented a new way to manage web services and all the related artifacts like configuration, tests or monitoring data in the Microsoft stack. It was based on the idea of using a lightweight SOA governance approach with a central repository exposed through RESTful services. At that point, we thought the same idea could be extended to enterprise applications in general by providing a generic repository for many of the runtime or design time artifacts generated during the development like configuration, application description or topology (a high level view of the components that made up a system), logging information or binaries. It took us several months to give a form to that idea and implement it as a product, but it is finally here and I am very proud to announce the release today under the name of “TeleSharp”. Telesharp provides in a nutshell the following features, 1. Configure your application topology in a central repository. Application topology in this context means that you can decompose your application and describe it in terms of components and how they interact each other. For example, you can tell that the CRM system is made up of a couple of WCF services and a ASP.NET MVC front end. 2. Centralize configuration for your applications and components.  You can import existing .NET configuration sections into the repository and associate them to the different components. In addition, environment overrides are supported for the configuration sections. We provide tooling and extensions in Visual Studio for managing all the configuration, and a set of powershell commands for automating the configuration deployment. 3. Browse all the assemblies and types remotely in your application servers in a web browser using an interface similar to any of the existing .NET reflection tools. You can easily determine this way whether the server is running the correct version of your applications. 4. Centralize logging and exception management into the repository. You get different reports and a pivot viewer experience for browsing all the different logging information generated by your applications. In addition, TeleSharp provides different providers for pushing the logging information to the central repository using well-known frameworks like ELMAH, Log4Net, EntLib or even Windows ETW.  The central repository itself is implemented as a set of OData services that any application can easily consume using regular Http. You can read more details in this introductory post If you think this product can be a good fit in your organization, you can request a trial version in our Tellago Studios website.

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• Service Testing made easy with SO-Aware Test Workbench

  - by cibrax

  I happy to announce today a new addition to our SO-Aware service repository toolset, SO-Aware Test Workbench, a WPF desktop application for doing functional and load testing against existing WCF Services. This tool is completely integrated to the SO-Aware service repository, which makes configuring new load and functional tests for WCF Soap and REST services a breeze. From now on, the service repository can play a very important role in an organization by facilitating collaboration between developers and testers. Developers can create and register new services in the repository with all the related artifacts like configuration. On the other hand, Testers can just pick one of the existing services in the repository and create functional or load tests from there, with no need to deal with specific details of the service implementation, location or configuration settings. Developers and Testers can later use the result of those tests to modify the services or adjust different settings on the tests or service configuration. Gustavo Machado, one of the developers behind this project, has written an excellent post describing all the functionality that can find today in the tool. You can also see the tool in action in this Endpoint Tv episode with Jesus and Ron Jacobs.

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• await, WhenAll, WaitAll, oh my!!

  - by cibrax

  If you are dealing with asynchronous work in .NET, you might know that the Task class has become the main driver for wrapping asynchronous calls. Although this class was officially introduced in .NET 4.0, the programming model for consuming tasks was much more simplified in C# 5.0 in .NET 4.5 with the addition of the new async/await keywords. In a nutshell, you can use these keywords to make asynchronous calls as if they were sequential, and avoiding in that way any fork or callback in the code. The compiler takes care of the rest. I was yesterday writing some code for making multiple asynchronous calls to backend services in parallel. The code looked as follow, var allResults = new List<Result>(); foreach(var provider in providers) { var results = await provider.GetResults(); allResults.AddRange(results); } return allResults; You see, I was using the await keyword to make multiple calls in parallel. Something I did not consider was the overhead this code implied after being compiled. I started an interesting discussion with some smart folks in twitter. One of them, Tugberk Ugurlu, had the brilliant idea of actually write some code to make a performance comparison with another approach using Task.WhenAll. There are two additional methods you can use to wait for the results of multiple calls in parallel, WhenAll and WaitAll. WhenAll creates a new task and waits for results in that new task, so it does not block the calling thread. WaitAll, on the other hand, blocks the calling thread. This is the code Tugberk initially wrote, and I modified afterwards to also show the results of WaitAll. class Program { private static Func<Stopwatch, Task>[] funcs = new Func<Stopwatch, Task>[] { async (watch) => { watch.Start(); await Task.Delay(1000); Console.WriteLine("1000 one has been completed."); }, async (watch) => { await Task.Delay(1500); Console.WriteLine("1500 one has been completed."); }, async (watch) => { await Task.Delay(2000); Console.WriteLine("2000 one has been completed."); watch.Stop(); Console.WriteLine(watch.ElapsedMilliseconds + "ms has been elapsed."); } }; static void Main(string[] args) { Console.WriteLine("Await in loop work starts..."); DoWorkAsync().ContinueWith(task => { Console.WriteLine("Parallel work starts..."); DoWorkInParallelAsync().ContinueWith(t => { Console.WriteLine("WaitAll work starts..."); WaitForAll(); }); }); Console.ReadLine(); } static async Task DoWorkAsync() { Stopwatch watch = new Stopwatch(); foreach (var func in funcs) { await func(watch); } } static async Task DoWorkInParallelAsync() { Stopwatch watch = new Stopwatch(); await Task.WhenAll(funcs[0](watch), funcs[1](watch), funcs[2](watch)); } static void WaitForAll() { Stopwatch watch = new Stopwatch(); Task.WaitAll(funcs[0](watch), funcs[1](watch), funcs[2](watch)); } } After running this code, the results were very concluding. Await in loop work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 4532ms has been elapsed. Parallel work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 2007ms has been elapsed. WaitAll work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 2009ms has been elapsed. The await keyword in a loop does not really make the calls in parallel.

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• SO-Aware Service Explorer – Configure and Export your services from VS 2010 into the repository

  - by cibrax

  We have introduced a new Visual Studio tool called “Service Explorer” as part of the new SO-Aware SDK version 1.3 to help developers to configure and export any regular WCF service into the SO-Aware service repository. This new tool is a regular Visual Studio Tool Window that can be opened from “View –> Other Windows –> Services Explorer”. Once you open the Services Explorer, you will able to see all the available WCF services in the Visual Studio Solution. In the image above, you can see that a “HelloWorld” service was found in the solution and listed under the Tool window on the left. There are two things you can do for a new service in tool, you can either export it to SO-Aware repository or associate it to an existing service version in the repository. Exporting the service to SO-Aware means that you want to create a new service version in the repository and associate the WCF service WSDL to that version. Associating the service means that you want to use a version already created in SO-Aware with the only purpose of managing and centralizing the service configuration in SO-Aware. The option for exporting a service will popup a dialog like the one bellow in which you can enter some basic information about the service version you want to create and the repository location. The option for associating a service will popup a dialog in which you can pick any existing service version repository and the application configuration file that you want to keep in sync for the service configuration. Two options are available for configuring a service, WCF Configuration or SO-Aware. The WCF Configuration option just tells the tool that the service will use the standard WCF configuration section “system.serviceModel” but that section must be updated and kept in sync with the configuration selected for the service in the repository. The SO-Aware configuration option will tell the tool that the service configuration will be resolved at runtime from the repository. For example, selecting SO-Aware will generate the following configuration in the selected application configuration file, <configuration> <configSections> <section name="serviceRepository" type="Tellago.ServiceModel.Governance.ServiceConfiguration.ServiceRepositoryConfigurationSection, Tellago.ServiceModel.Governance.ServiceConfiguration" /> </configSections> <serviceRepository url="http://localhost/soaware/servicerepository.svc"> <services> <service name="ref:HelloWorldService(1.0)@dev" type="SOAwareSampleService.HelloWorldService" /> </services> </serviceRepository> </configuration> As you can see the tool represents a great addition to the toolset that any developer can use to manage and centralize configuration for WCF services. In addition, it can be combined with other useful tools like WSCF.Blue (Web Service Contract First) for generating the service artifacts like schemas, service code or the service WSDL itself.

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