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• WLS MBeans

  - by Jani Rautiainen

  WLS provides a set of Managed Beans (MBeans) to configure, monitor and manage WLS resources. We can use the WLS MBeans to automate some of the tasks related to the configuration and maintenance of the WLS instance. The MBeans can be accessed a number of ways; using various UIs and programmatically using Java or WLST Python scripts.For customization development we can use the features to e.g. manage the deployed customization in MDS, control logging levels, automate deployment of dependent libraries etc. This article is an introduction on how to access and use the WLS MBeans. The goal is to illustrate the various access methods in a single article; the details of the features are left to the linked documentation.This article covers Windows based environment, steps for Linux would be similar however there would be some differences e.g. on how the file paths are defined. MBeansThe WLS MBeans can be categorized to runtime and configuration MBeans.The Runtime MBeans can be used to access the runtime information about the server and its resources. The data from runtime beans is only available while the server is running. The runtime beans can be used to e.g. check the state of the server or deployment.The Configuration MBeans contain information about the configuration of servers and resources. The configuration of the domain is stored in the config.xml file and the configuration MBeans can be used to access and modify the configuration data. For more information on the WLS MBeans refer to: Understanding WebLogic Server MBeans WLS MBean reference Java Management Extensions (JMX)We can use JMX APIs to access the WLS MBeans. This allows us to create Java programs to configure, monitor, and manage WLS resources. In order to use the WLS MBeans we need to add the following library into the class-path: WL_HOME\lib\wljmxclient.jar Connecting to a WLS MBean server The WLS MBeans are contained in a Mbean server, depending on the requirement we can connect to (MBean Server / JNDI Name): Domain Runtime MBean Server weblogic.management.mbeanservers.domainruntime Runtime MBean Server weblogic.management.mbeanservers.runtime Edit MBean Server weblogic.management.mbeanservers.edit To connect to the WLS MBean server first we need to create a map containing the credentials; Hashtable<String, String> param = new Hashtable<String, String>(); param.put(Context.SECURITY_PRINCIPAL, "weblogic");        param.put(Context.SECURITY_CREDENTIALS, "weblogic1");        param.put(JMXConnectorFactory.PROTOCOL_PROVIDER_PACKAGES, "weblogic.management.remote"); These define the user, password and package containing the protocol. Next we create the connection: JMXServiceURL serviceURL =     new JMXServiceURL("t3","127.0.0.1",7101,     "/jndi/weblogic.management.mbeanservers.domainruntime"); JMXConnector connector = JMXConnectorFactory.connect(serviceURL, param); MBeanServerConnection connection = connector.getMBeanServerConnection(); With the connection we can now access the MBeans for the WLS instance. For a complete example see Appendix A of this post. For more details refer to Accessing WebLogic Server MBeans with JMX Accessing WLS MBeans The WLS MBeans are structured hierarchically; in order to access content we need to know the path to the MBean we are interested in. The MBean is accessed using “MBeanServerConnection. getAttribute” API.  WLS provides entry points to the hierarchy allowing us to navigate all the WLS MBeans in the hierarchy (MBean Server / JMX object name): Domain Runtime MBean Server com.bea:Name=DomainRuntimeService,Type=weblogic.management.mbeanservers.domainruntime.DomainRuntimeServiceMBean Runtime MBean Servers com.bea:Name=RuntimeService,Type=weblogic.management.mbeanservers.runtime.RuntimeServiceMBean Edit MBean Server com.bea:Name=EditService,Type=weblogic.management.mbeanservers.edit.EditServiceMBean For example we can access the Domain Runtime MBean using: ObjectName service = new ObjectName( "com.bea:Name=DomainRuntimeService," + "Type=weblogic.management.mbeanservers.domainruntime.DomainRuntimeServiceMBean"); Same syntax works for any “child” WLS MBeans e.g. to find out all application deployments we can: ObjectName domainConfig = (ObjectName)connection.getAttribute(service,"DomainConfiguration"); ObjectName[] appDeployments = (ObjectName[])connection.getAttribute(domainConfig,"AppDeployments"); Alternatively we could access the same MBean using the full syntax: ObjectName domainConfig = new ObjectName("com.bea:Location=DefaultDomain,Name=DefaultDomain,Type=Domain"); ObjectName[] appDeployments = (ObjectName[])connection.getAttribute(domainConfig,"AppDeployments"); For more details refer to Accessing WebLogic Server MBeans with JMX Invoking operations on WLS MBeans The WLS MBean operations can be invoked with MBeanServerConnection. invoke API; in the following example we query the state of “AppsLoggerService” application: ObjectName appRuntimeStateRuntime = new ObjectName("com.bea:Name=AppRuntimeStateRuntime,Type=AppRuntimeStateRuntime"); Object[] parameters = { "AppsLoggerService", "DefaultServer" }; String[] signature = { "java.lang.String", "java.lang.String" }; String result = (String)connection.invoke(appRuntimeStateRuntime,"getCurrentState",parameters, signature); The result returned should be "STATE_ACTIVE" assuming the "AppsLoggerService" application is up and running. WebLogic Scripting Tool (WLST) The WebLogic Scripting Tool (WLST) is a command-line scripting environment that we can access the same WLS MBeans. The tool is located under: $MW_HOME\oracle_common\common\bin\wlst.bat Do note that there are several instances of the wlst script under the $MW_HOME, each of them works, however the commands available vary, so we want to use the one under “oracle_common”. The tool is started in offline mode. In offline mode we can access and manipulate the domain configuration. In online mode we can access the runtime information. We connect to the Administration Server : connect("weblogic","weblogic1", "t3://127.0.0.1:7101") In both online and offline modes we can navigate the WLS MBean using commands like "ls" to print content and "cd" to navigate between objects, for example: All the commands available can be obtained with: help('all') For details of the tool refer to WebLogic Scripting Tool and for the commands available WLST Command and Variable Reference. Also do note that the WLST tool can be invoked from Java code in Embedded Mode. Running Scripts The WLST tool allows us to automate tasks using Python scripts in Script Mode. The script can be manually created or recorded by the WLST tool. Example commands of recording a script: startRecording("c:/temp/recording.py") <commands that we want to record> stopRecording() We can run the script from WLST: execfile("c:/temp/recording.py") We can also run the script from the command line: C:\apps\Oracle\Middleware\oracle_common\common\bin\wlst.cmd c:/temp/recording.py There are various sample scripts are provided with the WLS instance. UI to Access the WLS MBeans There are various UIs through which we can access the WLS MBeans. Oracle Enterprise Manager Fusion Middleware Control Oracle WebLogic Server Administration Console Fusion Middleware Control MBean Browser In the integrated JDeveloper environment only the Oracle WebLogic Server Administration Console is available to us. For more information refer to the documentation, one noteworthy feature in the console is the ability to record WLST scripts based on the navigation. In addition to the UIs above the JConsole included in the JDK can be used to access the WLS MBeans. The JConsole needs to be started with specific parameter to force WLS objects to be used and jar files in the classpath: "C:\apps\Oracle\Middleware\jdk160_24\bin\jconsole" -J-Djava.class.path=C:\apps\Oracle\Middleware\jdk160_24\lib\jconsole.jar;C:\apps\Oracle\Middleware\jdk160_24\lib\tools.jar;C:\apps\Oracle\Middleware\wlserver_10.3\server\lib\wljmxclient.jar -J-Djmx.remote.protocol.provider.pkgs=weblogic.management.remote For more details refer to the Accessing Custom MBeans from JConsole. Summary In this article we have covered various ways we can access and use the WLS MBeans in context of integrated WLS in JDeveloper to be used for Fusion Application customization development. References Developing Custom Management Utilities With JMX for Oracle WebLogic Server Accessing WebLogic Server MBeans with JMX WebLogic Server MBean Reference WebLogic Scripting Tool WLST Command and Variable Reference Appendix A package oracle.apps.test; import java.io.IOException;import java.net.MalformedURLException;import java.util.Hashtable;import javax.management.MBeanServerConnection;import javax.management.MalformedObjectNameException;import javax.management.ObjectName;import javax.management.remote.JMXConnector;import javax.management.remote.JMXConnectorFactory;import javax.management.remote.JMXServiceURL;import javax.naming.Context;/** * This class contains simple examples on how to access WLS MBeans using JMX. */public class BlogExample {    /**     * Connection to the WLS MBeans     */    private MBeanServerConnection connection;    /**     * Constructor that takes in the connection information for the      * domain and obtains the resources from WLS MBeans using JMX.     * @param hostName host name to connect to for the WLS server     * @param port port to connect to for the WLS server     * @param userName user name to connect to for the WLS server     * @param password password to connect to for the WLS server     */    public BlogExample(String hostName, String port, String userName,                       String password) {        super();        try {            initConnection(hostName, port, userName, password);        } catch (Exception e) {            throw new RuntimeException("Unable to connect to the domain " +                                       hostName + ":" + port);        }    }    /**     * Default constructor.     * Tries to create connection with default values. Runtime exception will be     * thrown if the default values are not used in the local instance.     */    public BlogExample() {        this("127.0.0.1", "7101", "weblogic", "weblogic1");    }    /**     * Initializes the JMX connection to the WLS Beans     * @param hostName host name to connect to for the WLS server     * @param port port to connect to for the WLS server     * @param userName user name to connect to for the WLS server     * @param password password to connect to for the WLS server     * @throws IOException error connecting to the WLS MBeans     * @throws MalformedURLException error connecting to the WLS MBeans     * @throws MalformedObjectNameException error connecting to the WLS MBeans     */    private void initConnection(String hostName, String port, String userName,                                String password)                                 throws IOException, MalformedURLException,                                        MalformedObjectNameException {        String protocol = "t3";        String jndiroot = "/jndi/";        String mserver = "weblogic.management.mbeanservers.domainruntime";        JMXServiceURL serviceURL =            new JMXServiceURL(protocol, hostName, Integer.valueOf(port),                              jndiroot + mserver);        Hashtable<String, String> h = new Hashtable<String, String>();        h.put(Context.SECURITY_PRINCIPAL, userName);        h.put(Context.SECURITY_CREDENTIALS, password);        h.put(JMXConnectorFactory.PROTOCOL_PROVIDER_PACKAGES,              "weblogic.management.remote");        JMXConnector connector = JMXConnectorFactory.connect(serviceURL, h);        connection = connector.getMBeanServerConnection();    }    /**     * Main method used to invoke the logic for testing     * @param args arguments passed to the program     */    public static void main(String[] args) {        BlogExample blogExample = new BlogExample();        blogExample.testEntryPoint();        blogExample.testDirectAccess();        blogExample.testInvokeOperation();    }    /**     * Example of using an entry point to navigate the WLS MBean hierarchy.     */    public void testEntryPoint() {        try {            System.out.println("testEntryPoint");            ObjectName service =             new ObjectName("com.bea:Name=DomainRuntimeService,Type=" +"weblogic.management.mbeanservers.domainruntime.DomainRuntimeServiceMBean");            ObjectName domainConfig =                (ObjectName)connection.getAttribute(service,                                                    "DomainConfiguration");            ObjectName[] appDeployments =                (ObjectName[])connection.getAttribute(domainConfig,                                                      "AppDeployments");            for (ObjectName appDeployment : appDeployments) {                String resourceIdentifier =                    (String)connection.getAttribute(appDeployment,                                                    "SourcePath");                System.out.println(resourceIdentifier);            }        } catch (Exception e) {            throw new RuntimeException(e);        }    }    /**     * Example of accessing WLS MBean directly with a full reference.     * This does the same thing as testEntryPoint in slightly difference way.     */    public void testDirectAccess() {        try {            System.out.println("testDirectAccess");            ObjectName appDeployment =                new ObjectName("com.bea:Location=DefaultDomain,"+                               "Name=AppsLoggerService,Type=AppDeployment");            String resourceIdentifier =                (String)connection.getAttribute(appDeployment, "SourcePath");            System.out.println(resourceIdentifier);        } catch (Exception e) {            throw new RuntimeException(e);        }    }    /**     * Example of invoking operation on a WLS MBean.     */    public void testInvokeOperation() {        try {            System.out.println("testInvokeOperation");            ObjectName appRuntimeStateRuntime =                new ObjectName("com.bea:Name=AppRuntimeStateRuntime,"+                               "Type=AppRuntimeStateRuntime");            String identifier = "AppsLoggerService";            String serverName = "DefaultServer";            Object[] parameters = { identifier, serverName };            String[] signature = { "java.lang.String", "java.lang.String" };            String result =                (String)connection.invoke(appRuntimeStateRuntime, "getCurrentState",                                          parameters, signature);            System.out.println("State of " + identifier + " = " + result);        } catch (Exception e) {            throw new RuntimeException(e);        }    }}

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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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• ASP.NET and Silverlight Conference with Scott Guthrie and Visual Studio 2010 Launch!

  Hear Scott Guthrie and key speakers talk about Silverlight 4, ASP.NET 4.0, MVC, AJAX etc - and see how it’s all supported in Visual Studio 2010! We'll even throw in the global Launch of Visual Studio 2010! Early bird ends March 8!

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• ASP.NET Localization: Enabling resource expressions with an external resource assembly

  - by Brian Schroer

  I have several related projects that need the same localized text, so my global resources files are in a shared assembly that’s referenced by each of those projects. It took an embarrassingly long time to figure out how to have my .resx files generate “public” properties instead of “internal” so I could have a shared resources assembly (apparently it was pretty tricky pre-VS2008, and my “googling” bogged me down some out-of-date instructions). It’s easy though – Just change the “Custom Tool” to “PublicResXFileCodeGenerator”:    …which can be done via the “Access Modifier” dropdown of the resource file designer window:   A reference to my shared resources DLL gives me the ability to use the resources in code, but by default, the ASP.NET resource expression syntax: <asp:Button ID="BeerButton" runat="server" Text="<%$ Resources:MyResources, Beer %>" />   …assumes that your resources are in your web site project.   To make resource expressions work with my shared resources assembly, I added two classes to the resources assembly: 1) a custom IResourceProvider implementation:   1: using System; 2: using System.Web.Compilation; 3: using System.Globalization; 4:   5: namespace DuffBeer 6: { 7: public class CustomResourceProvider : IResourceProvider 8: { 9: public object GetObject(string resourceKey, CultureInfo culture) 10: { 11: return MyResources.ResourceManager.GetObject(resourceKey, culture); 12: } 13:   14: public System.Resources.IResourceReader ResourceReader 15: { 16: get { throw new NotSupportedException(); } 17: } 18: } 19: }   2) and a custom factory class inheriting from the ResourceProviderFactory base class:   1: using System; 2: using System.Web.Compilation; 3:   4: namespace DuffBeer 5: { 6: public class CustomResourceProviderFactory : ResourceProviderFactory 7: { 8: public override IResourceProvider CreateGlobalResourceProvider(string classKey) 9: { 10: return new CustomResourceProvider(); 11: } 12:   13: public override IResourceProvider CreateLocalResourceProvider(string virtualPath) 14: { 15: throw new NotSupportedException(String.Format( 16: "{0} does not support local resources.", 17: this.GetType().Name)); 18: } 19: } 20: }   In the “system.web / globalization” section of my web.config file, I point the “resourceProviderFactoryType" property to my custom factory:   <system.web> <globalization culture="auto:en-US" uiCulture="auto:en-US" resourceProviderFactoryType="DuffBeer.CustomResourceProviderFactory, DuffBeer" />   This simple approach met my needs for these projects , but if you want to create reusable resource provider and factory classes that allow you to specify the assembly in the resource expression, the instructions are here.

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• Shortcomings of using dynamic types in C#

  - by Karthik Sreenivasan

  I have been recently studying more on the dynamic types in C#. With some examples I understood once the code is compiled, it does not need to be recompiled again but can be executed directly. I feel the flexibility provided by the keyword to actually be able to change data type at will is a great advantage. Question, Are there any specific shortcomings apart from wrong dynamic method calls which throw run time exceptions which developers must know before starting the implementation.

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• Microsoft Semantic Search

  - by sqlartist

  This is something I really get excitied about - Microsoft Semantic Search. There is an excellent PDC demo and presentation here - http://microsoftpdc.com/Sessions/SVR32 . Intially I didn't think this was SQL related but I read that it may be included in future versions of SQL Server. For many years I have written linguistic, semantic, text extraction & clustering code in SQL Server for fun - now finally I can throw that all away and use this tool :) It reminds me of the Microsoft Research...(read more)

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• Deselect first row on gridview onload

  - by Suresh Behera

  I had situation to deselect the first gridview row on load and came to know IsSynchronizedWithCurrentItem on Gridview should able to that but some how i missed on gridview. Mean while below one should work void gvMain_RowLoaded( object sender, RowLoadedEventArgs e) { try { GridViewRow row = e.Row as GridViewRow; if (row != null && !firstItemExpanded) { row.DetailsVisibility = Visibility.Collapsed; firstItemExpanded = false ; } } catch (Exception ex) { throw ex; } } .csharpcode, .csharpcode...(read more)

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• Test interface implementation

  - by Michael

  I have a interface in our code base that I would like to be able to mock out for unit testing. I am writing a test implementation to allow the individual tests to be able to override the specific methods they are concerned with rather than implementing every method. I've run into a quandary over how the test implementation should behave if the test fails to override a method used by the method under test. Should I return a "non-value" (0, null) in the test implementation or throw a UnsupportedOperationException to explicitly fail the test?

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• Extending the ADF Controller exception handler

  - by frank.nimphius

  The Oracle ADF controller provides a declarative option for developers to define a view activity, method activity or router activity to handle exceptions in bounded or unbounded task flows. Exception handling however is for exceptions only and not handling all types of Throwable. Furthermore, exceptions that occur during the JSF RENDER RESPONSE phase are not looked at either as it is considered too late in the cycle. For developers to try themselves to handle unhandled exceptions in ADF Controller, it is possible to extend the default exception handling, while still leveraging the declarative configuration. To add your own exception handler: · Create a Java class that extends ExceptionHandler · Create a textfile with the name “oracle.adf.view.rich.context.Exceptionhandler” (without the quotes) and store it in .adf\META-INF\services (you need to create the “services” folder) · In the file, add the absolute name of your custom exception handler class (package name and class name without the “.class” extension) For any exception you don't handle in your custom exception handler, just re-throw it for the default handler to give it a try … import oracle.adf.view.rich.context.ExceptionHandler; public class MyCustomExceptionHandler extends ExceptionHandler { public MyCustomExceptionHandler() {      super(); } public void handleException(FacesContext facesContext,                              Throwable throwable, PhaseId phaseId)                              throws Throwable {    String error_message;    error_message = throwable.getMessage();    //check error message and handle it if you can    if( … ){          //handle exception        …    }    else{       //delegate to the default ADFc exception handler        throw throwable;}    } } Note however, that it is recommended to first try and handle exceptions with the ADF Controller default exception handling mechanism. In the past, I've seen attempts on OTN to handle regular application use cases with custom exception handlers for where there was no need to override the exception handler. So don't go for this solution to quickly and always think of alternative solutions. Sometimes a try-catch-final block does it better than sophisticated web exception handling.

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• Dynamically loading Assemblies to reduce Runtime Depencies

  - by Rick Strahl

  I've been working on a request to the West Wind Application Configuration library to add JSON support. The config library is a very easy to use code-first approach to configuration: You create a class that holds the configuration data that inherits from a base configuration class, and then assign a persistence provider at runtime that determines where and how the configuration data is store. Currently the library supports .NET Configuration stores (web.config/app.config), XML files, SQL records and string storage.About once a week somebody asks me about JSON support and I've deflected this question for the longest time because frankly I think that JSON as a configuration store doesn't really buy a heck of a lot over XML. Both formats require the user to perform some fixup of the plain configuration data - in XML into XML tags, with JSON using JSON delimiters for properties and property formatting rules. Sure JSON is a little less verbose and maybe a little easier to read if you have hierarchical data, but overall the differences are pretty minor in my opinion. And yet - the requests keep rolling in.Hard Link Issues in a Component LibraryAnother reason I've been hesitant is that I really didn't want to pull in a dependency on an external JSON library - in this case JSON.NET - into the core library. If you're not using JSON.NET elsewhere I don't want a user to have to require a hard dependency on JSON.NET unless they want to use the JSON feature. JSON.NET is also sensitive to versions and doesn't play nice with multiple versions when hard linked. For example, when you have a reference to V4.4 in your project but the host application has a reference to version 4.5 you can run into assembly load problems. NuGet's Update-Package can solve some of this *if* you can recompile, but that's not ideal for a component that's supposed to be just plug and play. This is no criticism of JSON.NET - this really applies to any dependency that might change.  So hard linking the DLL can be problematic for a number reasons, but the primary reason is to not force loading of JSON.NET unless you actually need it when you use the JSON configuration features of the library.Enter Dynamic LoadingSo rather than adding an assembly reference to the project, I decided that it would be better to dynamically load the DLL at runtime and then use dynamic typing to access various classes. This allows me to run without a hard assembly reference and allows more flexibility with version number differences now and in the future.But there are also a couple of downsides:No assembly reference means only dynamic access - no compiler type checking or IntellisenseRequirement for the host application to have reference to JSON.NET or else get runtime errorsThe former is minor, but the latter can be problematic. Runtime errors are always painful, but in this case I'm willing to live with this. If you want to use JSON configuration settings JSON.NET needs to be loaded in the project. If this is a Web project, it'll likely be there already.So there are a few things that are needed to make this work:Dynamically create an instance and optionally attempt to load an Assembly (if not loaded)Load types into dynamic variablesUse Reflection for a few tasks like statics/enumsThe dynamic keyword in C# makes the formerly most difficult Reflection part - method calls and property assignments - fairly painless. But as cool as dynamic is it doesn't handle all aspects of Reflection. Specifically it doesn't deal with object activation, truly dynamic (string based) member activation or accessing of non instance members, so there's still a little bit of work left to do with Reflection.Dynamic Object InstantiationThe first step in getting the process rolling is to instantiate the type you need to work with. This might be a two step process - loading the instance from a string value, since we don't have a hard type reference and potentially having to load the assembly. Although the host project might have a reference to JSON.NET, that instance might have not been loaded yet since it hasn't been accessed yet. In ASP.NET this won't be a problem, since ASP.NET preloads all referenced assemblies on AppDomain startup, but in other executable project, assemblies are just in time loaded only when they are accessed.Instantiating a type is a two step process: Finding the type reference and then activating it. Here's the generic code out of my ReflectionUtils library I use for this:/// <summary> /// Creates an instance of a type based on a string. Assumes that the type's /// </summary> /// <param name="typeName">Common name of the type</param> /// <param name="args">Any constructor parameters</param> /// <returns></returns> public static object CreateInstanceFromString(string typeName, params object[] args) { object instance = null; Type type = null; try { type = GetTypeFromName(typeName); if (type == null) return null; instance = Activator.CreateInstance(type, args); } catch { return null; } return instance; } /// <summary> /// Helper routine that looks up a type name and tries to retrieve the /// full type reference in the actively executing assemblies. /// </summary> /// <param name="typeName"></param> /// <returns></returns> public static Type GetTypeFromName(string typeName) { Type type = null; // Let default name binding find it type = Type.GetType(typeName, false); if (type != null) return type; // look through assembly list var assemblies = AppDomain.CurrentDomain.GetAssemblies(); // try to find manually foreach (Assembly asm in assemblies) { type = asm.GetType(typeName, false); if (type != null) break; } return type; } To use this for loading JSON.NET I have a small factory function that instantiates JSON.NET and sets a bunch of configuration settings on the generated object. The startup code also looks for failure and tries loading up the assembly when it fails since that's the main reason the load would fail. Finally it also caches the loaded instance for reuse (according to James the JSON.NET instance is thread safe and quite a bit faster when cached). Here's what the factory function looks like in JsonSerializationUtils:/// <summary> /// Dynamically creates an instance of JSON.NET /// </summary> /// <param name="throwExceptions">If true throws exceptions otherwise returns null</param> /// <returns>Dynamic JsonSerializer instance</returns> public static dynamic CreateJsonNet(bool throwExceptions = true) { if (JsonNet != null) return JsonNet; lock (SyncLock) { if (JsonNet != null) return JsonNet; // Try to create instance dynamic json = ReflectionUtils.CreateInstanceFromString("Newtonsoft.Json.JsonSerializer"); if (json == null) { try { var ass = AppDomain.CurrentDomain.Load("Newtonsoft.Json"); json = ReflectionUtils.CreateInstanceFromString("Newtonsoft.Json.JsonSerializer"); } catch (Exception ex) { if (throwExceptions) throw; return null; } } if (json == null) return null; json.ReferenceLoopHandling = (dynamic) ReflectionUtils.GetStaticProperty("Newtonsoft.Json.ReferenceLoopHandling", "Ignore"); // Enums as strings in JSON dynamic enumConverter = ReflectionUtils.CreateInstanceFromString("Newtonsoft.Json.Converters.StringEnumConverter"); json.Converters.Add(enumConverter); JsonNet = json; } return JsonNet; }This code's purpose is to return a fully configured JsonSerializer instance. As you can see the code tries to create an instance and when it fails tries to load the assembly, and then re-tries loading.Once the instance is loaded some configuration occurs on it. Specifically I set the ReferenceLoopHandling option to not blow up immediately when circular references are encountered. There are a host of other small config setting that might be useful to set, but the default seem to be good enough in recent versions. Note that I'm setting ReferenceLoopHandling which requires an Enum value to be set. There's no real easy way (short of using the cardinal numeric value) to set a property or pass parameters from static values or enums. This means I still need to use Reflection to make this work. I'm using the same ReflectionUtils class I previously used to handle this for me. The function looks up the type and then uses Type.InvokeMember() to read the static property.Another feature I need is have Enum values serialized as strings rather than numeric values which is the default. To do this I can use the StringEnumConverter to convert enums to strings by adding it to the Converters collection.As you can see there's still a bit of Reflection to be done even in C# 4+ with dynamic, but with a few helpers this process is relatively painless.Doing the actual JSON ConversionFinally I need to actually do my JSON conversions. For the Utility class I need serialization that works for both strings and files so I created four methods that handle these tasks two each for serialization and deserialization for string and file.Here's what the File Serialization looks like:/// <summary> /// Serializes an object instance to a JSON file. /// </summary> /// <param name="value">the value to serialize</param> /// <param name="fileName">Full path to the file to write out with JSON.</param> /// <param name="throwExceptions">Determines whether exceptions are thrown or false is returned</param> /// <param name="formatJsonOutput">if true pretty-formats the JSON with line breaks</param> /// <returns>true or false</returns> public static bool SerializeToFile(object value, string fileName, bool throwExceptions = false, bool formatJsonOutput = false) { dynamic writer = null; FileStream fs = null; try { Type type = value.GetType(); var json = CreateJsonNet(throwExceptions); if (json == null) return false; fs = new FileStream(fileName, FileMode.Create); var sw = new StreamWriter(fs, Encoding.UTF8); writer = Activator.CreateInstance(JsonTextWriterType, sw); if (formatJsonOutput) writer.Formatting = (dynamic)Enum.Parse(FormattingType, "Indented"); writer.QuoteChar = '"'; json.Serialize(writer, value); } catch (Exception ex) { Debug.WriteLine("JsonSerializer Serialize error: " + ex.Message); if (throwExceptions) throw; return false; } finally { if (writer != null) writer.Close(); if (fs != null) fs.Close(); } return true; }You can see more of the dynamic invocation in this code. First I grab the dynamic JsonSerializer instance using the CreateJsonNet() method shown earlier which returns a dynamic. I then create a JsonTextWriter and configure a couple of enum settings on it, and then call Serialize() on the serializer instance with the JsonTextWriter that writes the output to disk. Although this code is dynamic it's still fairly short and readable.For full circle operation here's the DeserializeFromFile() version:/// <summary> /// Deserializes an object from file and returns a reference. /// </summary> /// <param name="fileName">name of the file to serialize to</param> /// <param name="objectType">The Type of the object. Use typeof(yourobject class)</param> /// <param name="binarySerialization">determines whether we use Xml or Binary serialization</param> /// <param name="throwExceptions">determines whether failure will throw rather than return null on failure</param> /// <returns>Instance of the deserialized object or null. Must be cast to your object type</returns> public static object DeserializeFromFile(string fileName, Type objectType, bool throwExceptions = false) { dynamic json = CreateJsonNet(throwExceptions); if (json == null) return null; object result = null; dynamic reader = null; FileStream fs = null; try { fs = new FileStream(fileName, FileMode.Open, FileAccess.Read); var sr = new StreamReader(fs, Encoding.UTF8); reader = Activator.CreateInstance(JsonTextReaderType, sr); result = json.Deserialize(reader, objectType); reader.Close(); } catch (Exception ex) { Debug.WriteLine("JsonNetSerialization Deserialization Error: " + ex.Message); if (throwExceptions) throw; return null; } finally { if (reader != null) reader.Close(); if (fs != null) fs.Close(); } return result; }This code is a little more compact since there are no prettifying options to set. Here JsonTextReader is created dynamically and it receives the output from the Deserialize() operation on the serializer.You can take a look at the full JsonSerializationUtils.cs file on GitHub to see the rest of the operations, but the string operations are very similar - the code is fairly repetitive.These generic serialization utilities isolate the dynamic serialization logic that has to deal with the dynamic nature of JSON.NET, and any code that uses these functions is none the wiser that JSON.NET is dynamically loaded.Using the JsonSerializationUtils WrapperThe final consumer of the SerializationUtils wrapper is an actual ConfigurationProvider, that is responsible for handling reading and writing JSON values to and from files. The provider is simple a small wrapper around the SerializationUtils component and there's very little code to make this work now:The whole provider looks like this:/// <summary> /// Reads and Writes configuration settings in .NET config files and /// sections. Allows reading and writing to default or external files /// and specification of the configuration section that settings are /// applied to. /// </summary> public class JsonFileConfigurationProvider<TAppConfiguration> : ConfigurationProviderBase<TAppConfiguration> where TAppConfiguration: AppConfiguration, new() { /// <summary> /// Optional - the Configuration file where configuration settings are /// stored in. If not specified uses the default Configuration Manager /// and its default store. /// </summary> public string JsonConfigurationFile { get { return _JsonConfigurationFile; } set { _JsonConfigurationFile = value; } } private string _JsonConfigurationFile = string.Empty; public override bool Read(AppConfiguration config) { var newConfig = JsonSerializationUtils.DeserializeFromFile(JsonConfigurationFile, typeof(TAppConfiguration)) as TAppConfiguration; if (newConfig == null) { if(Write(config)) return true; return false; } DecryptFields(newConfig); DataUtils.CopyObjectData(newConfig, config, "Provider,ErrorMessage"); return true; } /// <summary> /// Return /// </summary> /// <typeparam name="TAppConfig"></typeparam> /// <returns></returns> public override TAppConfig Read<TAppConfig>() { var result = JsonSerializationUtils.DeserializeFromFile(JsonConfigurationFile, typeof(TAppConfig)) as TAppConfig; if (result != null) DecryptFields(result); return result; } /// <summary> /// Write configuration to XmlConfigurationFile location /// </summary> /// <param name="config"></param> /// <returns></returns> public override bool Write(AppConfiguration config) { EncryptFields(config); bool result = JsonSerializationUtils.SerializeToFile(config, JsonConfigurationFile,false,true); // Have to decrypt again to make sure the properties are readable afterwards DecryptFields(config); return result; } }This incidentally demonstrates how easy it is to create a new provider for the West Wind Application Configuration component. Simply implementing 3 methods will do in most cases.Note this code doesn't have any dynamic dependencies - all that's abstracted away in the JsonSerializationUtils(). From here on, serializing JSON is just a matter of calling the static methods on the SerializationUtils class.Already, there are several other places in some other tools where I use JSON serialization this is coming in very handy. With a couple of lines of code I was able to add JSON.NET support to an older AJAX library that I use replacing quite a bit of code that was previously in use. And for any other manual JSON operations (in a couple of apps I use JSON Serialization for 'blob' like document storage) this is also going to be handy.Performance?Some of you might be thinking that using dynamic and Reflection can't be good for performance. And you'd be right… In performing some informal testing it looks like the performance of the native code is nearly twice as fast as the dynamic code. Most of the slowness is attributable to type lookups. To test I created a native class that uses an actual reference to JSON.NET and performance was consistently around 85-90% faster with the referenced code. That being said though - I serialized 10,000 objects in 80ms vs. 45ms so this isn't hardly slouchy. For the configuration component speed is not that important because both read and write operations typically happen once on first access and then every once in a while. But for other operations - say a serializer trying to handle AJAX requests on a Web Server one would be well served to create a hard dependency.Dynamic Loading - Worth it?On occasion dynamic loading makes sense. But there's a price to be paid in added code complexity and a performance hit. But for some operations that are not pivotal to a component or application and only used under certain circumstances dynamic loading can be beneficial to avoid having to ship extra files and loading down distributions. These days when you create new projects in Visual Studio with 30 assemblies before you even add your own code, trying to keep file counts under control seems a good idea. It's not the kind of thing you do on a regular basis, but when needed it can be a useful tool. Hopefully some of you find this information useful…© Rick Strahl, West Wind Technologies, 2005-2013Posted in .NET  C#   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• The Brother DCP 8085DN Printer Is a good Small Business Asset

  The Brother DCP 8085DN printer can handle any printing task a small business can throw at it plus a whole lot more. By using the original Brother DCP 8085DN toner (http://www.qtoner.us/Brother-DCP-80... [Author: Ben Pate - Computers and Internet - March 25, 2010]

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• Subterranean IL: Exception handler semantics

  - by Simon Cooper

  In my blog posts on fault and filter exception handlers, I said that the same behaviour could be replicated using normal catch blocks. Well, that isn't entirely true... Changing the handler semantics Consider the following: .try { .try { .try { newobj instance void [mscorlib]System.Exception::.ctor() // IL for: // e.Data.Add("DictKey", true) throw } fault { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) endfault } } filter { ldstr "2a: Filter logic" call void [mscorlib]System.Console::WriteLine(string) // IL for: // (bool)((Exception)e).Data["DictKey"] endfilter }{ ldstr "2b: Filter handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } } catch object { ldstr "3: Catch handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } Return: // rest of method If the filter handler is engaged (true is inserted into the exception dictionary) then the filter handler gets engaged, and the following gets printed to the console: 2a: Filter logic 1: Fault handler 2b: Filter handler and if the filter handler isn't engaged, then the following is printed: 2a:Filter logic 1: Fault handler 3: Catch handler Filter handler execution The filter handler is executed first. Hmm, ok. Well, what happens if we replaced the fault block with the C# equivalent (with the exception dictionary value set to false)? .try { // throw exception } catch object { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) rethrow } we get this: 1: Fault handler 2a: Filter logic 3: Catch handler The fault handler is executed first, instead of the filter block. Eh? This change in behaviour is due to the way the CLR searches for exception handlers. When an exception is thrown, the CLR stops execution of the thread, and searches up the stack for an exception handler that can handle the exception and stop it propagating further - catch or filter handlers. It checks the type clause of catch clauses, and executes the code in filter blocks to see if the filter can handle the exception. When the CLR finds a valid handler, it saves the handler's location, then goes back to where the exception was thrown and executes fault and finally blocks between there and the handler location, discarding stack frames in the process, until it reaches the handler. So? By replacing a fault with a catch, we have changed the semantics of when the filter code is executed; by using a rethrow instruction, we've split up the exception handler search into two - one search to find the first catch, then a second when the rethrow instruction is encountered. This is only really obvious when mixing C# exception handlers with fault or filter handlers, so this doesn't affect code written only in C#. However it could cause some subtle and hard-to-debug effects with object initialization and ordering when using and calling code written in a language that can compile fault and filter handlers.

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• Pluggable Rules for Entity Framework Code First

  - by Ricardo Peres

  Suppose you want a system that lets you plug custom validation rules on your Entity Framework context. The rules would control whether an entity can be saved, updated or deleted, and would be implemented in plain .NET. Yes, I know I already talked about plugable validation in Entity Framework Code First, but this is a different approach. An example API is in order, first, a ruleset, which will hold the collection of rules: 1: public interface IRuleset : IDisposable 2: { 3: void AddRule<T>(IRule<T> rule); 4: IEnumerable<IRule<T>> GetRules<T>(); 5: } Next, a rule: 1: public interface IRule<T> 2: { 3: Boolean CanSave(T entity, DbContext ctx); 4: Boolean CanUpdate(T entity, DbContext ctx); 5: Boolean CanDelete(T entity, DbContext ctx); 6: String Name 7: { 8: get; 9: } 10: } Let’s analyze what we have, starting with the ruleset: Only has methods for adding a rule, specific to an entity type, and to list all rules of this entity type; By implementing IDisposable, we allow it to be cancelled, by disposing of it when we no longer want its rules to be applied. A rule, on the other hand: Has discrete methods for checking if a given entity can be saved, updated or deleted, which receive as parameters the entity itself and a pointer to the DbContext to which the ruleset was applied; Has a name property for helping us identifying what failed. A ruleset really doesn’t need a public implementation, all we need is its interface. The private (internal) implementation might look like this: 1: sealed class Ruleset : IRuleset 2: { 3: private readonly IDictionary<Type, HashSet<Object>> rules = new Dictionary<Type, HashSet<Object>>(); 4: private ObjectContext octx = null; 5:  6: internal Ruleset(ObjectContext octx) 7: { 8: this.octx = octx; 9: } 10:  11: public void AddRule<T>(IRule<T> rule) 12: { 13: if (this.rules.ContainsKey(typeof(T)) == false) 14: { 15: this.rules[typeof(T)] = new HashSet<Object>(); 16: } 17:  18: this.rules[typeof(T)].Add(rule); 19: } 20:  21: public IEnumerable<IRule<T>> GetRules<T>() 22: { 23: if (this.rules.ContainsKey(typeof(T)) == true) 24: { 25: foreach (IRule<T> rule in this.rules[typeof(T)]) 26: { 27: yield return (rule); 28: } 29: } 30: } 31:  32: public void Dispose() 33: { 34: this.octx.SavingChanges -= RulesExtensions.OnSaving; 35: RulesExtensions.rulesets.Remove(this.octx); 36: this.octx = null; 37:  38: this.rules.Clear(); 39: } 40: } Basically, this implementation: Stores the ObjectContext of the DbContext to which it was created for, this is so that later we can remove the association; Has a collection - a set, actually, which does not allow duplication - of rules indexed by the real Type of an entity (because of proxying, an entity may be of a type that inherits from the class that we declared); Has generic methods for adding and enumerating rules of a given type; Has a Dispose method for cancelling the enforcement of the rules. A (really dumb) rule applied to Product might look like this: 1: class ProductRule : IRule<Product> 2: { 3: #region IRule<Product> Members 4:  5: public String Name 6: { 7: get 8: { 9: return ("Rule 1"); 10: } 11: } 12:  13: public Boolean CanSave(Product entity, DbContext ctx) 14: { 15: return (entity.Price > 10000); 16: } 17:  18: public Boolean CanUpdate(Product entity, DbContext ctx) 19: { 20: return (true); 21: } 22:  23: public Boolean CanDelete(Product entity, DbContext ctx) 24: { 25: return (true); 26: } 27:  28: #endregion 29: } The DbContext is there because we may need to check something else in the database before deciding whether to allow an operation or not. And here’s how to apply this mechanism to any DbContext, without requiring the usage of a subclass, by means of an extension method: 1: public static class RulesExtensions 2: { 3: private static readonly MethodInfo getRulesMethod = typeof(IRuleset).GetMethod("GetRules"); 4: internal static readonly IDictionary<ObjectContext, Tuple<IRuleset, DbContext>> rulesets = new Dictionary<ObjectContext, Tuple<IRuleset, DbContext>>(); 5:  6: private static Type GetRealType(Object entity) 7: { 8: return (entity.GetType().Assembly.IsDynamic == true ? entity.GetType().BaseType : entity.GetType()); 9: } 10:  11: internal static void OnSaving(Object sender, EventArgs e) 12: { 13: ObjectContext octx = sender as ObjectContext; 14: IRuleset ruleset = rulesets[octx].Item1; 15: DbContext ctx = rulesets[octx].Item2; 16:  17: foreach (ObjectStateEntry entry in octx.ObjectStateManager.GetObjectStateEntries(EntityState.Added)) 18: { 19: Object entity = entry.Entity; 20: Type realType = GetRealType(entity); 21:  22: foreach (dynamic rule in (getRulesMethod.MakeGenericMethod(realType).Invoke(ruleset, null) as IEnumerable)) 23: { 24: if (rule.CanSave(entity, ctx) == false) 25: { 26: throw (new Exception(String.Format("Cannot save entity {0} due to rule {1}", entity, rule.Name))); 27: } 28: } 29: } 30:  31: foreach (ObjectStateEntry entry in octx.ObjectStateManager.GetObjectStateEntries(EntityState.Deleted)) 32: { 33: Object entity = entry.Entity; 34: Type realType = GetRealType(entity); 35:  36: foreach (dynamic rule in (getRulesMethod.MakeGenericMethod(realType).Invoke(ruleset, null) as IEnumerable)) 37: { 38: if (rule.CanDelete(entity, ctx) == false) 39: { 40: throw (new Exception(String.Format("Cannot delete entity {0} due to rule {1}", entity, rule.Name))); 41: } 42: } 43: } 44:  45: foreach (ObjectStateEntry entry in octx.ObjectStateManager.GetObjectStateEntries(EntityState.Modified)) 46: { 47: Object entity = entry.Entity; 48: Type realType = GetRealType(entity); 49:  50: foreach (dynamic rule in (getRulesMethod.MakeGenericMethod(realType).Invoke(ruleset, null) as IEnumerable)) 51: { 52: if (rule.CanUpdate(entity, ctx) == false) 53: { 54: throw (new Exception(String.Format("Cannot update entity {0} due to rule {1}", entity, rule.Name))); 55: } 56: } 57: } 58: } 59:  60: public static IRuleset CreateRuleset(this DbContext context) 61: { 62: Tuple<IRuleset, DbContext> ruleset = null; 63: ObjectContext octx = (context as IObjectContextAdapter).ObjectContext; 64:  65: if (rulesets.TryGetValue(octx, out ruleset) == false) 66: { 67: ruleset = rulesets[octx] = new Tuple<IRuleset, DbContext>(new Ruleset(octx), context); 68: 69: octx.SavingChanges += OnSaving; 70: } 71:  72: return (ruleset.Item1); 73: } 74: } It relies on the SavingChanges event of the ObjectContext to intercept the saving operations before they are actually issued. Yes, it uses a bit of dynamic magic! Very handy, by the way! So, let’s put it all together: 1: using (MyContext ctx = new MyContext()) 2: { 3: IRuleset rules = ctx.CreateRuleset(); 4: rules.AddRule(new ProductRule()); 5:  6: ctx.Products.Add(new Product() { Name = "xyz", Price = 50000 }); 7:  8: ctx.SaveChanges(); //an exception is fired here 9:  10: //when we no longer need to apply the rules 11: rules.Dispose(); 12: } Feel free to use it and extend it any way you like, and do give me your feedback! As a final note, this can be easily changed to support plain old Entity Framework (not Code First, that is), if that is what you are using.

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• Absolute statements in IT that are wrong

  - by Dan McGrath

  I was recently in a discussion about the absolute statement "It costs more in programming time to optimise software than it costs to throw hardware at a problem". The general thought (of which I agree with) is that as an absolute statement this is wrong. There are too many variables to ever generalise in such a way. What other statements do you hear about software/programming that simply do not work as an absolute and why?

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• Dynamically loading Assemblies to reduce Runtime Dependencies

  - by Rick Strahl

  I've been working on a request to the West Wind Application Configuration library to add JSON support. The config library is a very easy to use code-first approach to configuration: You create a class that holds the configuration data that inherits from a base configuration class, and then assign a persistence provider at runtime that determines where and how the configuration data is store. Currently the library supports .NET Configuration stores (web.config/app.config), XML files, SQL records and string storage.About once a week somebody asks me about JSON support and I've deflected this question for the longest time because frankly I think that JSON as a configuration store doesn't really buy a heck of a lot over XML. Both formats require the user to perform some fixup of the plain configuration data - in XML into XML tags, with JSON using JSON delimiters for properties and property formatting rules. Sure JSON is a little less verbose and maybe a little easier to read if you have hierarchical data, but overall the differences are pretty minor in my opinion. And yet - the requests keep rolling in.Hard Link Issues in a Component LibraryAnother reason I've been hesitant is that I really didn't want to pull in a dependency on an external JSON library - in this case JSON.NET - into the core library. If you're not using JSON.NET elsewhere I don't want a user to have to require a hard dependency on JSON.NET unless they want to use the JSON feature. JSON.NET is also sensitive to versions and doesn't play nice with multiple versions when hard linked. For example, when you have a reference to V4.4 in your project but the host application has a reference to version 4.5 you can run into assembly load problems. NuGet's Update-Package can solve some of this *if* you can recompile, but that's not ideal for a component that's supposed to be just plug and play. This is no criticism of JSON.NET - this really applies to any dependency that might change.  So hard linking the DLL can be problematic for a number reasons, but the primary reason is to not force loading of JSON.NET unless you actually need it when you use the JSON configuration features of the library.Enter Dynamic LoadingSo rather than adding an assembly reference to the project, I decided that it would be better to dynamically load the DLL at runtime and then use dynamic typing to access various classes. This allows me to run without a hard assembly reference and allows more flexibility with version number differences now and in the future.But there are also a couple of downsides:No assembly reference means only dynamic access - no compiler type checking or IntellisenseRequirement for the host application to have reference to JSON.NET or else get runtime errorsThe former is minor, but the latter can be problematic. Runtime errors are always painful, but in this case I'm willing to live with this. If you want to use JSON configuration settings JSON.NET needs to be loaded in the project. If this is a Web project, it'll likely be there already.So there are a few things that are needed to make this work:Dynamically create an instance and optionally attempt to load an Assembly (if not loaded)Load types into dynamic variablesUse Reflection for a few tasks like statics/enumsThe dynamic keyword in C# makes the formerly most difficult Reflection part - method calls and property assignments - fairly painless. But as cool as dynamic is it doesn't handle all aspects of Reflection. Specifically it doesn't deal with object activation, truly dynamic (string based) member activation or accessing of non instance members, so there's still a little bit of work left to do with Reflection.Dynamic Object InstantiationThe first step in getting the process rolling is to instantiate the type you need to work with. This might be a two step process - loading the instance from a string value, since we don't have a hard type reference and potentially having to load the assembly. Although the host project might have a reference to JSON.NET, that instance might have not been loaded yet since it hasn't been accessed yet. In ASP.NET this won't be a problem, since ASP.NET preloads all referenced assemblies on AppDomain startup, but in other executable project, assemblies are just in time loaded only when they are accessed.Instantiating a type is a two step process: Finding the type reference and then activating it. Here's the generic code out of my ReflectionUtils library I use for this:/// <summary> /// Creates an instance of a type based on a string. Assumes that the type's /// </summary> /// <param name="typeName">Common name of the type</param> /// <param name="args">Any constructor parameters</param> /// <returns></returns> public static object CreateInstanceFromString(string typeName, params object[] args) { object instance = null; Type type = null; try { type = GetTypeFromName(typeName); if (type == null) return null; instance = Activator.CreateInstance(type, args); } catch { return null; } return instance; } /// <summary> /// Helper routine that looks up a type name and tries to retrieve the /// full type reference in the actively executing assemblies. /// </summary> /// <param name="typeName"></param> /// <returns></returns> public static Type GetTypeFromName(string typeName) { Type type = null; // Let default name binding find it type = Type.GetType(typeName, false); if (type != null) return type; // look through assembly list var assemblies = AppDomain.CurrentDomain.GetAssemblies(); // try to find manually foreach (Assembly asm in assemblies) { type = asm.GetType(typeName, false); if (type != null) break; } return type; } To use this for loading JSON.NET I have a small factory function that instantiates JSON.NET and sets a bunch of configuration settings on the generated object. The startup code also looks for failure and tries loading up the assembly when it fails since that's the main reason the load would fail. Finally it also caches the loaded instance for reuse (according to James the JSON.NET instance is thread safe and quite a bit faster when cached). Here's what the factory function looks like in JsonSerializationUtils:/// <summary> /// Dynamically creates an instance of JSON.NET /// </summary> /// <param name="throwExceptions">If true throws exceptions otherwise returns null</param> /// <returns>Dynamic JsonSerializer instance</returns> public static dynamic CreateJsonNet(bool throwExceptions = true) { if (JsonNet != null) return JsonNet; lock (SyncLock) { if (JsonNet != null) return JsonNet; // Try to create instance dynamic json = ReflectionUtils.CreateInstanceFromString("Newtonsoft.Json.JsonSerializer"); if (json == null) { try { var ass = AppDomain.CurrentDomain.Load("Newtonsoft.Json"); json = ReflectionUtils.CreateInstanceFromString("Newtonsoft.Json.JsonSerializer"); } catch (Exception ex) { if (throwExceptions) throw; return null; } } if (json == null) return null; json.ReferenceLoopHandling = (dynamic) ReflectionUtils.GetStaticProperty("Newtonsoft.Json.ReferenceLoopHandling", "Ignore"); // Enums as strings in JSON dynamic enumConverter = ReflectionUtils.CreateInstanceFromString("Newtonsoft.Json.Converters.StringEnumConverter"); json.Converters.Add(enumConverter); JsonNet = json; } return JsonNet; }This code's purpose is to return a fully configured JsonSerializer instance. As you can see the code tries to create an instance and when it fails tries to load the assembly, and then re-tries loading.Once the instance is loaded some configuration occurs on it. Specifically I set the ReferenceLoopHandling option to not blow up immediately when circular references are encountered. There are a host of other small config setting that might be useful to set, but the default seem to be good enough in recent versions. Note that I'm setting ReferenceLoopHandling which requires an Enum value to be set. There's no real easy way (short of using the cardinal numeric value) to set a property or pass parameters from static values or enums. This means I still need to use Reflection to make this work. I'm using the same ReflectionUtils class I previously used to handle this for me. The function looks up the type and then uses Type.InvokeMember() to read the static property.Another feature I need is have Enum values serialized as strings rather than numeric values which is the default. To do this I can use the StringEnumConverter to convert enums to strings by adding it to the Converters collection.As you can see there's still a bit of Reflection to be done even in C# 4+ with dynamic, but with a few helpers this process is relatively painless.Doing the actual JSON ConversionFinally I need to actually do my JSON conversions. For the Utility class I need serialization that works for both strings and files so I created four methods that handle these tasks two each for serialization and deserialization for string and file.Here's what the File Serialization looks like:/// <summary> /// Serializes an object instance to a JSON file. /// </summary> /// <param name="value">the value to serialize</param> /// <param name="fileName">Full path to the file to write out with JSON.</param> /// <param name="throwExceptions">Determines whether exceptions are thrown or false is returned</param> /// <param name="formatJsonOutput">if true pretty-formats the JSON with line breaks</param> /// <returns>true or false</returns> public static bool SerializeToFile(object value, string fileName, bool throwExceptions = false, bool formatJsonOutput = false) { dynamic writer = null; FileStream fs = null; try { Type type = value.GetType(); var json = CreateJsonNet(throwExceptions); if (json == null) return false; fs = new FileStream(fileName, FileMode.Create); var sw = new StreamWriter(fs, Encoding.UTF8); writer = Activator.CreateInstance(JsonTextWriterType, sw); if (formatJsonOutput) writer.Formatting = (dynamic)Enum.Parse(FormattingType, "Indented"); writer.QuoteChar = '"'; json.Serialize(writer, value); } catch (Exception ex) { Debug.WriteLine("JsonSerializer Serialize error: " + ex.Message); if (throwExceptions) throw; return false; } finally { if (writer != null) writer.Close(); if (fs != null) fs.Close(); } return true; }You can see more of the dynamic invocation in this code. First I grab the dynamic JsonSerializer instance using the CreateJsonNet() method shown earlier which returns a dynamic. I then create a JsonTextWriter and configure a couple of enum settings on it, and then call Serialize() on the serializer instance with the JsonTextWriter that writes the output to disk. Although this code is dynamic it's still fairly short and readable.For full circle operation here's the DeserializeFromFile() version:/// <summary> /// Deserializes an object from file and returns a reference. /// </summary> /// <param name="fileName">name of the file to serialize to</param> /// <param name="objectType">The Type of the object. Use typeof(yourobject class)</param> /// <param name="binarySerialization">determines whether we use Xml or Binary serialization</param> /// <param name="throwExceptions">determines whether failure will throw rather than return null on failure</param> /// <returns>Instance of the deserialized object or null. Must be cast to your object type</returns> public static object DeserializeFromFile(string fileName, Type objectType, bool throwExceptions = false) { dynamic json = CreateJsonNet(throwExceptions); if (json == null) return null; object result = null; dynamic reader = null; FileStream fs = null; try { fs = new FileStream(fileName, FileMode.Open, FileAccess.Read); var sr = new StreamReader(fs, Encoding.UTF8); reader = Activator.CreateInstance(JsonTextReaderType, sr); result = json.Deserialize(reader, objectType); reader.Close(); } catch (Exception ex) { Debug.WriteLine("JsonNetSerialization Deserialization Error: " + ex.Message); if (throwExceptions) throw; return null; } finally { if (reader != null) reader.Close(); if (fs != null) fs.Close(); } return result; }This code is a little more compact since there are no prettifying options to set. Here JsonTextReader is created dynamically and it receives the output from the Deserialize() operation on the serializer.You can take a look at the full JsonSerializationUtils.cs file on GitHub to see the rest of the operations, but the string operations are very similar - the code is fairly repetitive.These generic serialization utilities isolate the dynamic serialization logic that has to deal with the dynamic nature of JSON.NET, and any code that uses these functions is none the wiser that JSON.NET is dynamically loaded.Using the JsonSerializationUtils WrapperThe final consumer of the SerializationUtils wrapper is an actual ConfigurationProvider, that is responsible for handling reading and writing JSON values to and from files. The provider is simple a small wrapper around the SerializationUtils component and there's very little code to make this work now:The whole provider looks like this:/// <summary> /// Reads and Writes configuration settings in .NET config files and /// sections. Allows reading and writing to default or external files /// and specification of the configuration section that settings are /// applied to. /// </summary> public class JsonFileConfigurationProvider<TAppConfiguration> : ConfigurationProviderBase<TAppConfiguration> where TAppConfiguration: AppConfiguration, new() { /// <summary> /// Optional - the Configuration file where configuration settings are /// stored in. If not specified uses the default Configuration Manager /// and its default store. /// </summary> public string JsonConfigurationFile { get { return _JsonConfigurationFile; } set { _JsonConfigurationFile = value; } } private string _JsonConfigurationFile = string.Empty; public override bool Read(AppConfiguration config) { var newConfig = JsonSerializationUtils.DeserializeFromFile(JsonConfigurationFile, typeof(TAppConfiguration)) as TAppConfiguration; if (newConfig == null) { if(Write(config)) return true; return false; } DecryptFields(newConfig); DataUtils.CopyObjectData(newConfig, config, "Provider,ErrorMessage"); return true; } /// <summary> /// Return /// </summary> /// <typeparam name="TAppConfig"></typeparam> /// <returns></returns> public override TAppConfig Read<TAppConfig>() { var result = JsonSerializationUtils.DeserializeFromFile(JsonConfigurationFile, typeof(TAppConfig)) as TAppConfig; if (result != null) DecryptFields(result); return result; } /// <summary> /// Write configuration to XmlConfigurationFile location /// </summary> /// <param name="config"></param> /// <returns></returns> public override bool Write(AppConfiguration config) { EncryptFields(config); bool result = JsonSerializationUtils.SerializeToFile(config, JsonConfigurationFile,false,true); // Have to decrypt again to make sure the properties are readable afterwards DecryptFields(config); return result; } }This incidentally demonstrates how easy it is to create a new provider for the West Wind Application Configuration component. Simply implementing 3 methods will do in most cases.Note this code doesn't have any dynamic dependencies - all that's abstracted away in the JsonSerializationUtils(). From here on, serializing JSON is just a matter of calling the static methods on the SerializationUtils class.Already, there are several other places in some other tools where I use JSON serialization this is coming in very handy. With a couple of lines of code I was able to add JSON.NET support to an older AJAX library that I use replacing quite a bit of code that was previously in use. And for any other manual JSON operations (in a couple of apps I use JSON Serialization for 'blob' like document storage) this is also going to be handy.Performance?Some of you might be thinking that using dynamic and Reflection can't be good for performance. And you'd be right… In performing some informal testing it looks like the performance of the native code is nearly twice as fast as the dynamic code. Most of the slowness is attributable to type lookups. To test I created a native class that uses an actual reference to JSON.NET and performance was consistently around 85-90% faster with the referenced code. This will change though depending on the size of objects serialized - the larger the object the more processing time is spent inside the actual dynamically activated components and the less difference there will be. Dynamic code is always slower, but how much it really affects your application primarily depends on how frequently the dynamic code is called in relation to the non-dynamic code executing. In most situations where dynamic code is used 'to get the process rolling' as I do here the overhead is small enough to not matter.All that being said though - I serialized 10,000 objects in 80ms vs. 45ms so this is hardly slouchy performance. For the configuration component speed is not that important because both read and write operations typically happen once on first access and then every once in a while. But for other operations - say a serializer trying to handle AJAX requests on a Web Server one would be well served to create a hard dependency.Dynamic Loading - Worth it?Dynamic loading is not something you need to worry about but on occasion dynamic loading makes sense. But there's a price to be paid in added code  and a performance hit which depends on how frequently the dynamic code is accessed. But for some operations that are not pivotal to a component or application and are only used under certain circumstances dynamic loading can be beneficial to avoid having to ship extra files adding dependencies and loading down distributions. These days when you create new projects in Visual Studio with 30 assemblies before you even add your own code, trying to keep file counts under control seems like a good idea. It's not the kind of thing you do on a regular basis, but when needed it can be a useful option in your toolset… © Rick Strahl, West Wind Technologies, 2005-2013Posted in .NET  C#   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• RemoveAll Dictionary Extension Method

  - by João Angelo

  Removing from a dictionary all the elements where the keys satisfy a set of conditions is something I needed to do more than once so I implemented it as an extension method to the IDictionary<TKey, TValue> interface. Here’s the code: public static class DictionaryExtensions { /// <summary> /// Removes all the elements where the key match the conditions defined by the specified predicate. /// </summary> /// <typeparam name="TKey"> /// The type of the dictionary key. /// </typeparam> /// <typeparam name="TValue"> /// The type of the dictionary value. /// </typeparam> /// <param name="dictionary"> /// A dictionary from which to remove the matched keys. /// </param> /// <param name="match"> /// The <see cref="Predicate{T}"/> delegate that defines the conditions of the keys to remove. /// </param> /// <exception cref="ArgumentNullException"> /// dictionary is null /// <br />-or-<br /> /// match is null. /// </exception> /// <returns> /// The number of elements removed from the <see cref="IDictionary{TKey, TValue}"/>. /// </returns> public static int RemoveAll<TKey, TValue>( this IDictionary<TKey, TValue> dictionary, Predicate<TKey> match) { if (dictionary == null) throw new ArgumentNullException("dictionary"); if (match == null) throw new ArgumentNullException("match"); var keysToRemove = dictionary.Keys.Where(k => match(k)).ToList(); if (keysToRemove.Count == 0) return 0; foreach (var key in keysToRemove) { dictionary.Remove(key); } return keysToRemove.Count; } }

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• Can throwing the iPhone high in the air launch my app or trigger desired function in iOS 7 or later

  - by aMother

  My app is an emergency app. It will be used by people in emergency and disasters. It's possible that they got stuck in situations where they just don't have the time to enter or draw their password, launch the appp and push a button. Is it possible that ask the OS to launch the app if user throw their iphone up in the air or shake it vigrously or something else. PS: I think it's possible with the accelerometer.

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• REST to Objects in C#

  RESTful interfaces for web services are all the rage for many Web 2.0 sites.  If you want to consume these in a very simple fashion, LINQ to XML can do the job pretty easily in C#.  If you go searching for help on this, youll find a lot of incomplete solutions and fairly large toolkits and frameworks (guess how I know this) this quick article is meant to be a no fluff just stuff approach to making this work. POCO Objects Lets assume you have a Model that you want to suck data into from a RESTful web service.  Ideally this is a Plain Old CLR Object, meaning it isnt infected with any persistence or serialization goop.  It might look something like this: public class Entry { public int Id; public int UserId; public DateTime Date; public float Hours; public string Notes; public bool Billable;   public override string ToString() { return String.Format("[{0}] User: {1} Date: {2} Hours: {3} Notes: {4} Billable {5}", Id, UserId, Date, Hours, Notes, Billable); } } Not that this isnt a completely trivial object.  Lets look at the API for the service.  RESTful HTTP Service In this case, its TickSpots API, with the following sample output: <?xml version="1.0" encoding="UTF-8"?> <entries type="array"> <entry> <id type="integer">24</id> <task_id type="integer">14</task_id> <user_id type="integer">3</user_id> <date type="date">2008-03-08</date> <hours type="float">1.00</hours> <notes>Had trouble with tribbles.</notes> <billable>true</billable> # Billable is an attribute inherited from the task <billed>true</billed> # Billed is an attribute to track whether the entry has been invoiced <created_at type="datetime">Tue, 07 Oct 2008 14:46:16 -0400</created_at> <updated_at type="datetime">Tue, 07 Oct 2008 14:46:16 -0400</updated_at> # The following attributes are derived and provided for informational purposes: <user_email>[email protected]</user_email> <task_name>Remove converter assembly</task_name> <sum_hours type="float">2.00</sum_hours> <budget type="float">10.00</budget> <project_name>Realign dilithium crystals</project_name> <client_name>Starfleet Command</client_name> </entry> </entries> Im assuming in this case that I dont necessarily care about all of the data fields the service is returning I just need some of them for my applications purposes.  Thus, you can see there are more elements in the <entry> XML than I have in my Entry class. Get The XML with C# The next step is to get the XML.  The following snippet does the heavy lifting once you pass it the appropriate URL: protected XElement GetResponse(string uri) { var request = WebRequest.Create(uri) as HttpWebRequest; request.UserAgent = ".NET Sample"; request.KeepAlive = false;   request.Timeout = 15 * 1000;   var response = request.GetResponse() as HttpWebResponse;   if (request.HaveResponse == true && response != null) { var reader = new StreamReader(response.GetResponseStream()); return XElement.Parse(reader.ReadToEnd()); } throw new Exception("Error fetching data."); } This is adapted from the Yahoo Developer article on Web Service REST calls.  Once you have the XML, the last step is to get the data back as your POCO. Use LINQ-To-XML to Deserialize POCOs from XML This is done via the following code: public IEnumerable<Entry> List(DateTime startDate, DateTime endDate) { string additionalParameters = String.Format("start_date={0}&end_date={1}", startDate.ToShortDateString(), endDate.ToShortDateString()); string uri = BuildUrl("entries", additionalParameters);   XElement elements = GetResponse(uri);   var entries = from e in elements.Elements() where e.Name.LocalName == "entry" select new Entry { Id = int.Parse(e.Element("id").Value), UserId = int.Parse(e.Element("user_id").Value), Date = DateTime.Parse(e.Element("date").Value), Hours = float.Parse(e.Element("hours").Value), Notes = e.Element("notes").Value, Billable = bool.Parse(e.Element("billable").Value) }; return entries; }   For completeness, heres the BuildUrl method for my TickSpot API wrapper: // Change these to your settings protected const string projectDomain = "DOMAIN.tickspot.com"; private const string authParams = "[email protected]&password=MyTickSpotPassword";   protected string BuildUrl(string apiMethod, string additionalParams) { if (projectDomain.Contains("DOMAIN")) { throw new ApplicationException("You must update your domain in ProjectRepository.cs."); } if (authParams.Contains("MyTickSpotPassword")) { throw new ApplicationException("You must update your email and password in ProjectRepository.cs."); } return string.Format("https://{0}/api/{1}?{2}&{3}", projectDomain, apiMethod, authParams, additionalParams); } Thats it!  Now go forth and consume XML and map it to classes you actually want to work with.  Have fun! Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Search Engine Optimization - The Death of SEO

  In the past it was very easy to optimize a website. All you had to do is create a strong title, write up a keyword rich description and throw in a few industry specific keywords to get your site to rank on the first page of Google, Yahoo, MSN (now Bing), etc.

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• SQL SERVER – QUOTED_IDENTIFIER ON/OFF Explanation and Example – Question on Real World Usage

  - by Pinal Dave

  This is a follow up blog post of SQL SERVER – QUOTED_IDENTIFIER ON/OFF and ANSI_NULL ON/OFF Explanation. I wrote that blog six years ago and I had plans that I will write a follow up blog post of the same. Today, when I was going over my to-do list and I was surprised that I had an item there which was six years old and I never got to do that. In the earlier blog post I wrote about exploitation of the Quoted Identifier and ANSI Null. In this blog post we will see a quick example of Quoted Identifier. However, before we continue this blog post, let us see a refresh what both of Quoted Identifider do. QUOTED IDENTIFIER ON/OFF This option specifies the setting for use of double quotes. When this is on, double quotation mark is used as part of the SQL Server identifier (object name). This can be useful in situations in which identifiers are also SQL Server reserved words. In simple words when we have QUOTED IDENTIFIER ON, anything which is wrapped in double quotes becomes an object. E.g. -- The following will work SET QUOTED_IDENTIFIER ON GO CREATE DATABASE "Test1" GO -- The following will throw an error about Incorrect syntax near 'Test2'. SET QUOTED_IDENTIFIER OFF GO CREATE DATABASE "Test2" GO This feature is particularly helpful when we are working with reserved keywords in SQL Server. For example if you have to create a database with the name VARCHAR or INT or DATABASE you may want to put double quotes around your database name and turn on quoted identifiers to create a database with the such name. Personally, I do not think so anybody will ever create a database with the reserve keywords intentionally, as it will just lead to confusion. Here is another example to give you further clarity about how Quoted Idenifier setting works with SELECT statement. -- The following will throw an error about Invalid column name 'Column'. SET QUOTED_IDENTIFIER ON GO SELECT "Column" GO -- The following will work SET QUOTED_IDENTIFIER OFF GO SELECT "Column" GO Personally, I always use the following method to create database as it works irrespective of what is the quoted identifier’s status. It always creates objects with my desire name whenever I would like to create. CREATE DATABASE [Test3] I believe the future of the quoted identifier on or off is useful in the real world when we have script generated from another database where this setting was ON and we have to now execute the same script again in our environment again. Question to you - I personally have never used this feature as I mentioned earlier. I believe this feature is there to support the scripts which are generated in another SQL Database or generate the script for other database. Do you have a real world scenario where we need to turn on or off Quoted Identifiers. Click to Download Scripts Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• How far has a bug pushed you? [closed]

  - by Darknight

  When debugging (hard to find) bugs, I know I've personally gotten so frustrated as to lash out on the keyboard and shout profanities at the monitor. I have repeatability witnessed co-workers throw their computer mouse off the table in anger and frustration. What is the furthest a bastard of bug has ever pushed you? EDIT: Hehehe :D it would seem this bug, er I mean post has pushed the guys to close it... Oh well, very very interesting answers anyway.

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• If your unit test code "smells" does it really matter?

  - by Buttons840

  Usually I just throw my unit tests together using copy and paste and all kind of other bad practices. The unit tests usually end up looking quite ugly, they're full of "code smell," but does this really matter? I always tell myself as long as the "real" code is "good" that's all that matters. Plus, unit testing usually requires various "smelly hacks" like stubbing functions. How concerned should I be over poorly designed ("smelly") unit tests?

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• The Brother MFC 7820n Printer Fuels Well-Organized Corporations

  When the Brother MFC 7820N printer is put to the efficiency test, it passes quite easily and places ahead of the leading competitors. Any job an office can throw at it, it can accomplish. In addition... [Author: Ben Pate - Computers and Internet - March 25, 2010]

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• Throwing exception from a property when my object state is invalid

  - by Rumi P.

  Microsoft guidelines say: "Avoid throwing exceptions from property getters", and I normally follow that. But my application uses Linq2SQL, and there is the case where my object can be in invalid state because somebody or something wrote nonsense into the database. Consider this toy example: [Table(Name="Rectangle")] public class Rectangle { [Column(Name="ID", IsPrimaryKey = true, IsDbGenerated = true)] public int ID {get; set;} [Column(Name="firstSide")] public double firstSide {get; set;} [Column(Name="secondSide")] public double secondSide {get; set;} public double sideRatio { get { return firstSide/secondSide; } } } Here, I could write code which ensures that my application never writes a Rectangle with a zero-length side into the database. But no matter how bulletproof I make my own code, somebody could open the database with a different application and create an invalid Rectangle, especially one with a 0 for secondSide. (For this example, please forget that it is possible to design the database in a way such that writing a side length of zero into the rectangle table is impossible; my domain model is very complex and there are constraints on model state which cannot be expressed in a relational database). So, the solution I am gravitating to is to change the getter to: get { if(firstSide > 0 && secondSide > 0) return firstSide/secondSide; else throw new System.InvalidOperationException("All rectangle sides should have a positive length"); } The reasoning behind not throwing exceptions from properties is that programmers should be able to use them without having to make precautions about catching and handling them them. But in this case, I think that it is OK to continue to use this property without such precautions: if the exception is thrown because my application wrote a non-zero rectangle side into the database, then this is a serious bug. It cannot and shouldn't be handled in the application, but there should be code which prevents it. It is good that the exception is visibly thrown, because that way the bug is caught. if the exception is thrown because a different application changed the data in the database, then handling it is outside of the scope of my application. So I can't do anything about it if I catch it. Is this a good enough reasoning to get over the "avoid" part of the guideline and throw the exception? Or should I turn it into a method after all? Note that in the real code, the properties which can have an invalid state feel less like the result of a calculation, so they are "natural" properties, not methods.

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• How do you make it so when you click an app on the side it jumps to the opened app

  - by Matt

  I'm not sure what I did but I had it so I could click on the icon that split it into 4 screens and throw whatever I wanted on whichever screen I wanted but I fiddled around with some stuff and made it so that now when I click on the app, say I have Firefox open but it isn't on the active page, it does nothing. Whereas before in the same situation when I clicked on the active app it would sling me across to whichever of the four screens it was located on; how do I get back to this setting?

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