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• WPF Login Verification Using Active Directory

  - by psheriff

  Back in October of 2009 I created a WPF login screen (Figure 1) that just showed how to create the layout for a login screen. That one sample is probably the most downloaded sample we have. So in this blog post, I thought I would update that screen and also hook it up to show how to authenticate your user against Active Directory. Figure 1: Original WPF Login Screen I have updated not only the code behind for this login screen, but also the look and feel as shown in Figure 2. Figure 2: An Updated WPF Login Screen The UI To create the UI for this login screen you can refer to my October of 2009 blog post to see how to create the borderless window. You can then look at the sample code to see how I created the linear gradient brush for the background. There are just a few differences in this screen compared to the old version. First, I changed the key image and instead of using words for the Cancel and Login buttons, I used some icons. Secondly I added a text box to hold the Domain name that you wish to authenticate against. This text box is automatically filled in if you are connected to a network. In the Window_Loaded event procedure of the winLogin window you can retrieve the user’s domain name from the Environment.UserDomainName property. For example: txtDomain.Text = Environment.UserDomainName The ADHelper Class Instead of coding the call to authenticate the user directly in the login screen I created an ADHelper class. This will make it easier if you want to add additional AD calls in the future. The ADHelper class contains just one method at this time called AuthenticateUser. This method authenticates a user name and password against the specified domain. The login screen will gather the credentials from the user such as their user name and password, and also the domain name to authenticate against. To use this ADHelper class you will need to add a reference to the System.DirectoryServices.dll in .NET. The AuthenticateUser Method In order to authenticate a user against your Active Directory you will need to supply a valid LDAP path string to the constructor of the DirectoryEntry class. The LDAP path string will be in the format LDAP://DomainName. You will also pass in the user name and password to the constructor of the DirectoryEntry class as well. With a DirectoryEntry object populated with this LDAP path string, the user name and password you will now pass this object to the constructor of a DirectorySearcher object. You then perform the FindOne method on the DirectorySearcher object. If the DirectorySearcher object returns a SearchResult then the credentials supplied are valid. If the credentials are not valid on the Active Directory then an exception is thrown. C#public bool AuthenticateUser(string domainName, string userName,  string password){  bool ret = false;   try  {    DirectoryEntry de = new DirectoryEntry("LDAP://" + domainName,                                           userName, password);    DirectorySearcher dsearch = new DirectorySearcher(de);    SearchResult results = null;     results = dsearch.FindOne();     ret = true;  }  catch  {    ret = false;  }   return ret;} Visual Basic Public Function AuthenticateUser(ByVal domainName As String, _ ByVal userName As String, ByVal password As String) As Boolean  Dim ret As Boolean = False   Try    Dim de As New DirectoryEntry("LDAP://" & domainName, _                                 userName, password)    Dim dsearch As New DirectorySearcher(de)    Dim results As SearchResult = Nothing     results = dsearch.FindOne()     ret = True  Catch    ret = False  End Try   Return retEnd Function In the Click event procedure under the Login button you will find the following code that will validate the credentials that the user types into the login window. C#private void btnLogin_Click(object sender, RoutedEventArgs e){  ADHelper ad = new ADHelper();   if(ad.AuthenticateUser(txtDomain.Text,         txtUserName.Text, txtPassword.Password))    DialogResult = true;  else    MessageBox.Show("Unable to Authenticate Using the                      Supplied Credentials");} Visual BasicPrivate Sub btnLogin_Click(ByVal sender As Object, _ ByVal e As RoutedEventArgs)  Dim ad As New ADHelper()   If ad.AuthenticateUser(txtDomain.Text, txtUserName.Text, _                         txtPassword.Password) Then    DialogResult = True  Else    MessageBox.Show("Unable to Authenticate Using the                      Supplied Credentials")  End IfEnd Sub Displaying the Login Screen At some point when your application launches, you will need to display your login screen modally. Below is the code that you would call to display the login form (named winLogin in my sample application). This code is called from the main application form, and thus the owner of the login screen is set to “this”. You then call the ShowDialog method on the login screen to have this form displayed modally. After the user clicks on one of the two buttons you need to check to see what the DialogResult property was set to. The DialogResult property is a nullable type and thus you first need to check to see if the value has been set. C# private void DisplayLoginScreen(){  winLogin win = new winLogin();   win.Owner = this;  win.ShowDialog();  if (win.DialogResult.HasValue && win.DialogResult.Value)    MessageBox.Show("User Logged In");  else    this.Close();} Visual Basic Private Sub DisplayLoginScreen()  Dim win As New winLogin()   win.Owner = Me  win.ShowDialog()  If win.DialogResult.HasValue And win.DialogResult.Value Then    MessageBox.Show("User Logged In")  Else    Me.Close()  End IfEnd Sub Summary Creating a nice looking login screen is fairly simple to do in WPF. Using the Active Directory services from a WPF application should make your desktop programming task easier as you do not need to create your own user authentication system. I hope this article gave you some ideas on how to create a login screen in WPF. NOTE: You can download the complete sample code for this blog entry at my website: http://www.pdsa.com/downloads. Click on Tips & Tricks, then select 'WPF Login Verification Using Active Directory' from the drop down list. Good Luck with your Coding,Paul Sheriff ** SPECIAL OFFER FOR MY BLOG READERS **We frequently offer a FREE gift for readers of my blog. Visit http://www.pdsa.com/Event/Blog for your FREE gift!

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• How I understood monads, part 1/2: sleepless and self-loathing in Seattle

  - by Bertrand Le Roy

  For some time now, I had been noticing some interest for monads, mostly in the form of unintelligible (to me) blog posts and comments saying “oh, yeah, that’s a monad” about random stuff as if it were absolutely obvious and if I didn’t know what they were talking about, I was probably an uneducated idiot, ignorant about the simplest and most fundamental concepts of functional programming. Fair enough, I am pretty much exactly that. Being the kind of guy who can spend eight years in college just to understand a few interesting concepts about the universe, I had to check it out and try to understand monads so that I too can say “oh, yeah, that’s a monad”. Man, was I hit hard in the face with the limitations of my own abstract thinking abilities. All the articles I could find about the subject seemed to be vaguely understandable at first but very quickly overloaded the very few concept slots I have available in my brain. They also seemed to be consistently using arcane notation that I was entirely unfamiliar with. It finally all clicked together one Friday afternoon during the team’s beer symposium when Louis was patient enough to break it down for me in a language I could understand (C#). I don’t know if being intoxicated helped. Feel free to read this with or without a drink in hand. So here it is in a nutshell: a monad allows you to manipulate stuff in interesting ways. Oh, OK, you might say. Yeah. Exactly. Let’s start with a trivial case: public static class Trivial { public static TResult Execute<T, TResult>( this T argument, Func<T, TResult> operation) { return operation(argument); } } This is not a monad. I removed most concepts here to start with something very simple. There is only one concept here: the idea of executing an operation on an object. This is of course trivial and it would actually be simpler to just apply that operation directly on the object. But please bear with me, this is our first baby step. Here’s how you use that thing: "some string" .Execute(s => s + " processed by trivial proto-monad.") .Execute(s => s + " And it's chainable!"); What we’re doing here is analogous to having an assembly chain in a factory: you can feed it raw material (the string here) and a number of machines that each implement a step in the manufacturing process and you can start building stuff. The Trivial class here represents the empty assembly chain, the conveyor belt if you will, but it doesn’t care what kind of raw material gets in, what gets out or what each machine is doing. It is pure process. A real monad will need a couple of additional concepts. Let’s say the conveyor belt needs the material to be processed to be contained in standardized boxes, just so that it can safely and efficiently be transported from machine to machine or so that tracking information can be attached to it. Each machine knows how to treat raw material or partly processed material, but it doesn’t know how to treat the boxes so the conveyor belt will have to extract the material from the box before feeding it into each machine, and it will have to box it back afterwards. This conveyor belt with boxes is essentially what a monad is. It has one method to box stuff, one to extract stuff from its box and one to feed stuff into a machine. So let’s reformulate the previous example but this time with the boxes, which will do nothing for the moment except containing stuff. public class Identity<T> { public Identity(T value) { Value = value; } public T Value { get; private set;} public static Identity<T> Unit(T value) { return new Identity<T>(value); } public static Identity<U> Bind<U>( Identity<T> argument, Func<T, Identity<U>> operation) { return operation(argument.Value); } } Now this is a true to the definition Monad, including the weird naming of the methods. It is the simplest monad, called the identity monad and of course it does nothing useful. Here’s how you use it: Identity<string>.Bind( Identity<string>.Unit("some string"), s => Identity<string>.Unit( s + " was processed by identity monad.")).Value That of course is seriously ugly. Note that the operation is responsible for re-boxing its result. That is a part of strict monads that I don’t quite get and I’ll take the liberty to lift that strange constraint in the next examples. To make this more readable and easier to use, let’s build a few extension methods: public static class IdentityExtensions { public static Identity<T> ToIdentity<T>(this T value) { return new Identity<T>(value); } public static Identity<U> Bind<T, U>( this Identity<T> argument, Func<T, U> operation) { return operation(argument.Value).ToIdentity(); } } With those, we can rewrite our code as follows: "some string".ToIdentity() .Bind(s => s + " was processed by monad extensions.") .Bind(s => s + " And it's chainable...") .Value; This is considerably simpler but still retains the qualities of a monad. But it is still pointless. Let’s look at a more useful example, the state monad, which is basically a monad where the boxes have a label. It’s useful to perform operations on arbitrary objects that have been enriched with an attached state object. public class Stateful<TValue, TState> { public Stateful(TValue value, TState state) { Value = value; State = state; } public TValue Value { get; private set; } public TState State { get; set; } } public static class StateExtensions { public static Stateful<TValue, TState> ToStateful<TValue, TState>( this TValue value, TState state) { return new Stateful<TValue, TState>(value, state); } public static Stateful<TResult, TState> Execute<TValue, TState, TResult>( this Stateful<TValue, TState> argument, Func<TValue, TResult> operation) { return operation(argument.Value) .ToStateful(argument.State); } } You can get a stateful version of any object by calling the ToStateful extension method, passing the state object in. You can then execute ordinary operations on the values while retaining the state: var statefulInt = 3.ToStateful("This is the state"); var processedStatefulInt = statefulInt .Execute(i => ++i) .Execute(i => i * 10) .Execute(i => i + 2); Console.WriteLine("Value: {0}; state: {1}", processedStatefulInt.Value, processedStatefulInt.State); This monad differs from the identity by enriching the boxes. There is another way to give value to the monad, which is to enrich the processing. An example of that is the writer monad, which can be typically used to log the operations that are being performed by the monad. Of course, the richest monads enrich both the boxes and the processing. That’s all for today. I hope with this you won’t have to go through the same process that I did to understand monads and that you haven’t gone into concept overload like I did. Next time, we’ll examine some examples that you already know but we will shine the monadic light, hopefully illuminating them in a whole new way. Realizing that this pattern is actually in many places but mostly unnoticed is what will enable the truly casual “oh, yes, that’s a monad” comments. Here’s the code for this article: http://weblogs.asp.net/blogs/bleroy/Samples/Monads.zip The Wikipedia article on monads: http://en.wikipedia.org/wiki/Monads_in_functional_programming This article was invaluable for me in understanding how to express the canonical monads in C# (interesting Linq stuff in there): http://blogs.msdn.com/b/wesdyer/archive/2008/01/11/the-marvels-of-monads.aspx

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• A WPF Image Button

  - by psheriff

  Instead of a normal button with words, sometimes you want a button that is just graphical. Yes, you can put an Image control in the Content of a normal Button control, but you still have the button outline, and trying to change the style can be rather difficult. Instead I like creating a user control that simulates a button, but just accepts an image. Figure 1 shows an example of three of these custom user controls to represent minimize, maximize and close buttons for a borderless window. Notice the highlighted image button has a gray rectangle around it. You will learn how to highlight using the VisualStateManager in this blog post.Figure 1: Creating a custom user control for things like image buttons gives you complete control over the look and feel.I would suggest you read my previous blog post on creating a custom Button user control as that is a good primer for what I am going to expand upon in this blog post. You can find this blog post at http://weblogs.asp.net/psheriff/archive/2012/08/10/create-your-own-wpf-button-user-controls.aspx.The User ControlThe XAML for this image button user control contains just a few controls, plus a Visual State Manager. The basic outline of the user control is shown below:<Border Grid.Row="0"        Name="borMain"        Style="{StaticResource pdsaButtonImageBorderStyle}"        MouseEnter="borMain_MouseEnter"        MouseLeave="borMain_MouseLeave"        MouseLeftButtonDown="borMain_MouseLeftButtonDown">  <VisualStateManager.VisualStateGroups>  ... MORE XAML HERE ...  </VisualStateManager.VisualStateGroups>  <Image Style="{StaticResource pdsaButtonImageImageStyle}"         Visibility="{Binding Path=Visibility}"         Source="{Binding Path=ImageUri}"         ToolTip="{Binding Path=ToolTip}" /></Border>There is a Border control named borMain and a single Image control in this user control. That is all that is needed to display the buttons shown in Figure 1. The definition for this user control is in a DLL named PDSA.WPF. The Style definitions for both the Border and the Image controls are contained in a resource dictionary names PDSAButtonStyles.xaml. Using a resource dictionary allows you to create a few different resource dictionaries, each with a different theme for the buttons.The Visual State ManagerTo display the highlight around the button as your mouse moves over the control, you will need to add a Visual State Manager group. Two different states are needed; MouseEnter and MouseLeave. In the MouseEnter you create a ColorAnimation to modify the BorderBrush color of the Border control. You specify the color to animate as “DarkGray”. You set the duration to less than a second. The TargetName of this storyboard is the name of the Border control “borMain” and since we are specifying a single color, you need to set the TargetProperty to “BorderBrush.Color”. You do not need any storyboard for the MouseLeave state. Leaving this VisualState empty tells the Visual State Manager to put everything back the way it was before the MouseEnter event.<VisualStateManager.VisualStateGroups>  <VisualStateGroup Name="MouseStates">    <VisualState Name="MouseEnter">      <Storyboard>        <ColorAnimation             To="DarkGray"            Duration="0:0:00.1"            Storyboard.TargetName="borMain"            Storyboard.TargetProperty="BorderBrush.Color" />      </Storyboard>    </VisualState>    <VisualState Name="MouseLeave" />  </VisualStateGroup></VisualStateManager.VisualStateGroups>Writing the Mouse EventsTo trigger the Visual State Manager to run its storyboard in response to the specified event, you need to respond to the MouseEnter event on the Border control. In the code behind for this event call the GoToElementState() method of the VisualStateManager class exposed by the user control. To this method you will pass in the target element (“borMain”) and the state (“MouseEnter”). The VisualStateManager will then run the storyboard contained within the defined state in the XAML.private void borMain_MouseEnter(object sender,  MouseEventArgs e){  VisualStateManager.GoToElementState(borMain,    "MouseEnter", true);}You also need to respond to the MouseLeave event. In this event you call the VisualStateManager as well, but specify “MouseLeave” as the state to go to.private void borMain_MouseLeave(object sender, MouseEventArgs e){  VisualStateManager.GoToElementState(borMain,     "MouseLeave", true);}The Resource DictionaryBelow is the definition of the PDSAButtonStyles.xaml resource dictionary file contained in the PDSA.WPF DLL. This dictionary can be used as the default look and feel for any image button control you add to a window. <ResourceDictionary  ... >  <!-- ************************* -->  <!-- ** Image Button Styles ** -->  <!-- ************************* -->  <!-- Image/Text Button Border -->  <Style TargetType="Border"         x:Key="pdsaButtonImageBorderStyle">    <Setter Property="Margin"            Value="4" />    <Setter Property="Padding"            Value="2" />    <Setter Property="BorderBrush"            Value="Transparent" />    <Setter Property="BorderThickness"            Value="1" />    <Setter Property="VerticalAlignment"            Value="Top" />    <Setter Property="HorizontalAlignment"            Value="Left" />    <Setter Property="Background"            Value="Transparent" />  </Style>  <!-- Image Button -->  <Style TargetType="Image"         x:Key="pdsaButtonImageImageStyle">    <Setter Property="Width"            Value="40" />    <Setter Property="Margin"            Value="6" />    <Setter Property="VerticalAlignment"            Value="Top" />    <Setter Property="HorizontalAlignment"            Value="Left" />  </Style></ResourceDictionary>Using the Button ControlOnce you make a reference to the PDSA.WPF DLL from your WPF application you will see the “PDSAucButtonImage” control appear in your Toolbox. Drag and drop the button onto a Window or User Control in your application. I have not referenced the PDSAButtonStyles.xaml file within the control itself so you do need to add a reference to this resource dictionary somewhere in your application such as in the App.xaml.<Application.Resources>  <ResourceDictionary>    <ResourceDictionary.MergedDictionaries>      <ResourceDictionary         Source="/PDSA.WPF;component/PDSAButtonStyles.xaml" />    </ResourceDictionary.MergedDictionaries>  </ResourceDictionary></Application.Resources>This will give your buttons a default look and feel unless you override that dictionary on a specific Window or User Control or on an individual button. After you have given a global style to your application and you drag your image button onto a window, the following will appear in your XAML window.<my:PDSAucButtonImage ... />There will be some other attributes set on the above XAML, but you simply need to set the x:Name, the ToolTip and ImageUri properties. You will also want to respond to the Click event procedure in order to associate an action with clicking on this button. In the sample code you download for this blog post you will find the declaration of the Minimize button to be the following:<my:PDSAucButtonImage       x:Name="btnMinimize"       Click="btnMinimize_Click"       ToolTip="Minimize Application"       ImageUri="/PDSA.WPF;component/Images/Minus.png" />The ImageUri property is a dependency property in the PDSAucButtonImage user control. The x:Name and the ToolTip we get for free. You have to create the Click event procedure yourself. This is also created in the PDSAucButtonImage user control as follows:private void borMain_MouseLeftButtonDown(object sender,  MouseButtonEventArgs e){  RaiseClick(e);}public delegate void ClickEventHandler(object sender,  RoutedEventArgs e);public event ClickEventHandler Click;protected void RaiseClick(RoutedEventArgs e){  if (null != Click)    Click(this, e);}Since a Border control does not have a Click event you will create one by using the MouseLeftButtonDown on the border to fire an event you create called “Click”.SummaryCreating your own image button control can be done in a variety of ways. In this blog post I showed you how to create a custom user control and simulate a button using a Border and Image control. With just a little bit of code to respond to the MouseLeftButtonDown event on the border you can raise your own Click event. Dependency properties, such as ImageUri, allow you to set attributes on your custom user control. Feel free to expand on this button by adding additional dependency properties, change the resource dictionary, and even the animation to make this button look and act like you want.NOTE: You can download the sample code for this article by visiting my website at http://www.pdsa.com/downloads. Select “Tips & Tricks”, then select “A WPF Image  Button” from the drop down list.

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• As a C# developer, would you learn Java to develop for Android or use MonoDroid instead?

  - by Dan Tao

  I'd consider myself pretty well versed in C#. It's my language of choice at the moment, and it's where basically all my professional experience lies. Still, I'm puzzled by the existence of the MonoDroid project. My understanding has always been that C# and Java are very close. Like, if you know one, you can learn the other really quickly. So, as I've considered developing my first Android app, I just assumed I would familiarize myself with Java enough to get started and then just sort of learn as I go. Wouldn't this make more sense than using MonoDroid, which is likely to be less feature-rich than the Java Android SDK, and requires learning its own API (albeit a .NET API) anyway? I just feel like it would be better to learn a new language (and an extremely popular one at that) and get some experience in it—when it's so close to what you already know anyway—rather than stick with a technology you're experienced with, without gaining any more valuable skills. Maybe I'm grossly misrepresenting the average potential MonoDroid user. Maybe it's more for people who are experienced in Java and .NET and just prefer .NET. Or maybe (in fact it's likely) there are other factors I just haven't considered. I'm just wondering, why would you use MonoDroid instead of just developing for Android using Java?

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• What are some of the benefits of a "Micro-ORM"?

  - by Wayne M

  I've been looking into the so-called "Micro ORMs" like Dapper and (to a lesser extent as it relies on .NET 4.0) Massive as these might be easier to implement at work than a full-blown ORM since our current system is highly reliant on stored procedures and would require significant refactoring to work with an ORM like NHibernate or EF. What is the benefit of using one of these over a full-featured ORM? It seems like just a thin layer around a database connection that still forces you to write raw SQL - perhaps I'm wrong but I was always told the reason for ORMs in the first place is so you didn't have to write SQL, it could be automatically generated; especially for multi-table joins and mapping relationships between tables which are a pain to do in pure SQL but trivial with an ORM. For instance, looking at an example of Dapper: var connection = new SqlConnection(); // setup here... var person = connection.Query<Person>("select * from people where PersonId = @personId", new { PersonId = 42 }); How is that any different than using a handrolled ADO.NET data layer, except that you don't have to write the command, set the parameters and I suppose map the entity back using a Builder. It looks like you could even use a stored procedure call as the SQL string. Are there other tangible benefits that I'm missing here where a Micro ORM makes sense to use? I'm not really seeing how it's saving anything over the "old" way of using ADO.NET except maybe a few lines of code - you still have to write to figure out what SQL you need to execute (which can get hairy) and you still have to map relationships between tables (the part that IMHO ORMs help the most with).

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• Highlighting rows and columns in an HTML table using JQuery

  - by nikolaosk

  A friend of mine was seeking some help regarding HTML tables and JQuery. I have decided to write a few posts demonstrating the various techniques I used with JQuery to achieve the desired functionality. ?here are other posts in my blog regarding JQuery.You can find them all here.I have received some comments from visitors of this blog that are "complaining" about the length of the blog posts. I will not write lengthy posts anymore...I mean I will try not to do so..We will demonstrate this with a step by step example. I will use Visual Studio 2012 Ultimate. You can also use Visual Studio 2012 Express Edition. You can also use VS 2010 editions. 1) Launch Visual Studio. Create an ASP.Net Empty Web application. Choose an appropriate name for your application.2) Add a web form, default.aspx page to the application.3) Add a table from the HTML controls tab control (from the Toolbox) on the default.aspx page4) Now we need to download the JQuery library. Please visit the http://jquery.com/ and download the minified version.5) We will add a stylesheet to the application (Style.css)5) Obviously at some point we need to reference the JQuery library and the external stylesheet. In the head section ? add the following lines.   <link href="Style.css" rel="stylesheet" type="text/css" />       <script src="jquery-1_8_2_min.js" type="text/javascript"></script> 6) Now we need to highlight the rows when the user hovers over them.7) First we need to type the HTML markup<body>    <form id="form1" runat="server">    <div>        <h1>Liverpool Legends</h1>        <table style="width: 50%;" border="1" cellpadding="10" cellspacing ="10">            <thead>                <tr><th>Defenders</th><th>MidFielders</th><th>Strikers</th></tr>            </thead>            <tbody>            <tr>                <td>Alan Hansen</td>                <td>Graeme Souness</td>                <td>Ian Rush</td>            </tr>            <tr>                <td>Alan Kennedy</td>                <td>Steven Gerrard</td>                <td>Michael Owen</td>            </tr>            <tr>                <td>Jamie Garragher</td>                <td>Kenny Dalglish</td>                <td>Robbie Fowler</td>            </tr>            <tr>                <td>Rob Jones</td>                <td>Xabi Alonso</td>                <td>Dirk Kuyt</td>            </tr>                </tbody>        </table>            </div>    </form></body>8) Now we need to write the simple rules in the style.css file.body{background-color:#eaeaea;}.hover { background-color:#42709b; color:#ff6a00;} 8) Inside the head section we also write the simple JQuery code.  <script type="text/javascript"> $(document).ready(function() { $('tr').hover( function() { $(this).find('td').addClass('hover'); }, function() { $(this).find('td').removeClass('hover'); } ); }); </script>9) Run your application and see the row changing background color and text color every time the user hovers over it. Let me explain how this functionality is achieved.We have the .hover style rule in the style.css file that contains some properties that define the background color value and the color value when the mouse will be hovered on the row.In the JQuery code we do attach the hover() event to the tr elements.The function that is called when the hovering takes place, we search for the td element and through the addClass function we apply the styles defined in the .hover class rule in the style.css file.I remove the .hover rule styles with the removeClass function. Now let's say that we want to highlight only alternate rows of the table.We need to add another rule in the style.css.alternate { background-color:#42709b; color:#ff6a00;} The JQuery code (comment out the previous JQuery code) follows  <script type="text/javascript">        $(document).ready(function() {                     $('table tr:odd').addClass('alternate');        });    </script>  When I run my application through VS I see the following result You can do that with columns as well. You can highlight alternate columns as well.The JQuery code (comment out the previous JQuery code) follows  <script type="text/javascript">        $(document).ready(function() {                      $('td:nth-child(odd)').addClass('alternate');        });    </script>  In this script I use the nth-child() method in the JQuery code.This method retrieves all the elements that are nth children of their parent.Have a look at the picture below to see the resultsYou can also change color to each individual cell when hovered on.The JQuery code (comment out the previous JQuery code) follows    <script type="text/javascript">        $(document).ready(function() {          $('td').hover(                  function() {                 $(this).addClass('hover');               },                function() {                    $(this).removeClass('hover');                }                );        });    </script> Have a look at the picture below to see the results. Hope it helps!!!

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• Clustering and custom applications

  - by Ahmed ilyas

  I was not entirely sure what tags to put but hope this is ok. This is just a general question in regards to clustering and applications: so lets say we have a clustered environment setup. We cluster SQL Server (I dont know exactly how its done but lets just say its been done for the sake of argument). Now if a website or application is trying to access that database for read/write (say an ASP.NET app or a C# Winforms app) and during that time SQL goes down - it takes a couple of minutes for the clustering failover to take affect to switch to another node. What happens during this time? I think it will time out/unable to connect. BUT is there a way for it to place the request in some pipeline so when the cluster node is back up/switched over it will continue as normal? as you can see, I know nothing much about clustering! what about your own custom .NET apps? Would there be a special way to develop them? I know that you can say create a simple Hello world app, and cluster that but they wouldnt be something you could see interms of the UI or anything, so they would effectively need to be developed as a Windows Service perhaps or even as a standard Console app which runs and not wait for user input but you wouldnt see any output from it (unless you redirect output to somewhere else) What im getting at here is... for those who have experience or developed a cluster application in .NET, how did you do it and what are the things to be aware of? For example we have the cloud service - fundamentally its built on clustering - if there is an outage, another node takes place and service is resumed as normal but we dont really see much of that downtime.

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• Need advice for approach for a web-based app that loads excel worksheet but exposes only the charts

  - by John

  I'm looking for suggestions on the Visual Studio approach to take for a web application that is in the conceptual stage. My environment has a lot of tools: Windows Server 2008 R2 Standard 64bit Visual Studio 2010 Professional Edition Sharepoint 2010 Server Enterprise Edition SQL Server 2008 R2 Office 2010 Professional I know I will need this app to retrieve data from a database (or a web service - not sure exactly at this point). The data needs to be placed in an Excel workbook dynamically. The app will need to have a nice user interface (standard web controls - perhaps with some Javascript effects). The Excel ribbon and worksheet grid will need to be hidden. Some web control(s) will cause the Excel chart(s) to be rendered. I am thinking this sounds like Visual Studio Tools for Office (VSTO) so as to leverage .Net and hide Excel. Can you offer suggestions regarding: One ASP.Net Web App Project One Class Library Project for Excel or perhaps which one of the several different Excel 2010 project types (addin, template, document) Would Excel Services for Sharepoint be useful (or required) ? I am feeling a little overwhelmed with so many choices at this early stage of conceptualizing the app. Can you suggest some ideas for this sort of thing? Also, I am a bit more experienced with C# but I've read VB.Net is better for work with the Excel object model. What are general advises with regard to tool choice and overall approach tradeoffs?

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• Is it possible to use a VB master page to cover an entirely separate directory written in C#?

  - by Jason Weber

  I have a company website written in vb.net. There are 5 master pages. I recently began utilizing a forum application, also asp.net 4.0, but this one is written in C#. My forum directory is domain.com/knowledgebase/. Is there any possible way to take one of my vb.net master pages and somehow integrate into the /knowledgebase/ directory? Here's what's currently This is what's in the top of every page in my site: <%@ Page Title="USS Vision Inc." Language="VB" MasterPageFile="~/homepage.master" AutoEventWireup="false" CodeFile="default.aspx.vb" Inherits="_default" culture="auto" meta:resourcekey="PageResource1" uiculture="auto" Debug="true" %> This is what's in my /knowledgebase/ directory: <%@ Page Language="C#" AutoEventWireup="true" ValidateRequest="false" Inherits="YAF.ForumPageBase" culture="auto" uiculture="auto" %> <%@ Register TagPrefix="YAF" Assembly="YAF" Namespace="YAF" %> <script runat="server"> Is it somehow possible to use, for instance, homepage.master in the /knowledgebase/ directory? If so, how would I accomplish this? Thanks for any guidance anybody can offer!

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• Designing a system with different business rules for different customers

  - by user1595846

  My company is rewriting our proprietary business application. The current architecture is poorly done and inflexible. It is coded more procedural oriented as opposed to object oriented. It has become difficult to maintain. Our system is a web application written in .Net Webforms. I am considering ASP.Net MVC for the rewrite. We intend to rewrite it with a good, solid architecture with the goal of maintainability and reusable classes for some of our other systems and services. We would also like the system to be customizable for different customers in the event that we market the system. I am considering redesigning the system based on the layered architecture (Presentation, Business, Data Access layers) described in the Microsoft Patterns and Practices Application Architecture Guide. http://msdn.microsoft.com/en-us/library/ff650706.aspx Hopefully this isn't too open ended, but how would you recommend allowing for different business logic/rules for different customers? I'm aware of Windows Workflow Foundation, but from what I've read about it, it seems many business rules could be too complicated to handle there. Also, Can anyone point me to where I can download an example of a .net solution that is based on the Application Architecture Guide? I have already downloaded the Layered Architecture Solution Guidance and the Expense Sample on codeplex. I was looking for something a bit larger and more robust that I could step through the code and see how it works. If you feel there are better architectures to base our redesign on please feel free to share. I appreciate your help!

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• What exactly is bootstrap admin-template and how it is supposed to be used

  - by Leron

  So this is my second ASP.NET MVC 4 project. It's decided that for this one we will use this template and it was said in a way that I felt really stupid for not knowing how exactly this template will help us and what exactly we gain by using it. I'm used to using HTML/CSS for the UI combined with jQuery. Now it seems that instead of jQuery we will be using bootstrap which as far as I understand is just another JS library created from twitter, so if that's it then this part is clear. What I really need to clarify for myself is what exactly this theme is used for, what is offering, why one would want to use such a theme? From what I see in the live demo maybe it's just a stack of premade controls that you can use in the front end along with bootstrap.js and maybe I'm just confused because on the page is shown as much as possible just for presentational purposes. If that's right, still I wonder where I can find info for the current theme, the controls that it offers and the functionality that I get and not least - how to use it. But still those are just my assumptions. What I really need is a clarification on what exactly is this theme for, what is the advantage using it, is there a good tutorials about how to use such themes in the context of ASP.NET MVC 3+. Also any additional info about this theme and generally on using themes in ASP.NET MVC will be much appreciated.

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• Persisting high score table in flash game without a network. (Featuring: HttpListenerException)

  - by bearcdp

  Hi everyone, this question is very programming-centric, but it's for a game so I figured I might as well post it here. I'm doing polishing work on a GGJ '11 game because it will be shown at an indie arcade tomorrow afternoon, and they're expecting our final build in the morning. We'd like to have a high score table that displays during attract mode, but since it's Flash (Flixel) it would require some networking, Mochi, or something to keep a record of these scores. Only problem is the machine we'd be running on probably won't have network access. As a quick solution, I thought I'd just write up a dinky little high score server in C#/.NET that could take basic GET requests for submitting scores and getting the score list. We're talking REAL basic, like blocking while waiting for an incoming request, run & forget console app, etc. There's no guarantee that our .swf won't get reloaded, and we'd like the scores to persist, so this server would pretty much exists to keep a safe copy of the scores that the game can add to and request, and occasionally the server will write the scores to a flat text file. But, HttpListener is giving me Error Code 87 'The parameter is incorrect.' Have any idea what I'm doing wrong? Or better yet, am I barking up the wrong tree and missing an obviously simpler solution? This is all I've got so far in my Main(): HttpListener listener = new HttpListener(); listener.Prefixes.Add("http://localhost:66666/"); listener.Start(); The exception happens at listener.Start(); and the stack trace is: at System.Net.HttpListener.AddAllPrefixes() at System.Net.HttpListener.Start() at WOSEBCE_ScoreServer.Program.Main(String[] args) in C:\Users\Michael\Documents\Visual Studio 2010\VS2010 Projects\WOSEBCE_ScoreServer\WOSEBCE_ScoreServer\Program.cs:line 24 at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart()

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• Is there a massive other side to software development which I've somehow missed, revolving entirely around Microsoft?

  - by Aerovistae

  I'm still a beginning programmer; I've been at it for 2 years. I've learned to work with a few languages, a bit of web development technologies, a handful of libraries, frameworks, and IDEs. But over the past two years (and long before I even started, really), I keep hearing references to these...things. A million of them. Things such as C#, ADO, SOAP, ASP, ASP.NET, the .NET framework, CLR, F#, etc etc. And I've read their Wikipedia articles, in-depth, multiple times, and they all mention a million other things on that list, but I just can't seem to grasp what it all is. The only thing I've taken away with any certainty is that Microsoft is behind all of it. It sounds almost like a conspiracy. Are all these technologies just for developing on the Windows platform? What is .NET? Do some software developers dedicate their entire career just to that side of things? Why would I want to get into it, and what advantage does...whatever it is...have over all the other technologies there are? I hope this makes sense. It's a broad question, but inside it there's a very specific question asking about something I don't know the name of. Hopefully you can grasp my confusion.

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• IIS7Register failed with HRESULT 800700b7: 'Cannot create a file when that file already exists.'

  - by Optimax

  I am trying to re-install ASP.NET on IIS7 running in Win7/64, which magically stopped working all of as sudden. When I run aspnet_regiis -i, I get an error message that says Finished installing ASP.NET (4.0.30319). Setup has detected some errors during the operation. For details, please read the setup log file C:\Users\username\AppData\Local\Temp\ASPNETSetup_00031.log Looking at the log, it reports Failure Changing IIS ApplicationHost.config: IIS7Register failed with HRESULT 800700b7: 'Cannot create a file when that file already exists. ' The real problem surfaces when trying to access an ASP.NET web page from that server: HTTP Error 500.21 - Internal Server Error Handler "PageHandlerFactory-Integrated" has a bad module "ManagedPipelineHandler" in its module list and Most likely causes: Managed handler is used; however, ASP.NET is not installed or is not installed completely. There is a typographical error in the configuration for the handler module list. So it seems ASP.NET has NOT been properly re-installed. Now, I am aware of the alleged one-and-only remedy for this, repeated all over the Web, and referenced for example here: http://blogs.msdn.com/b/dougste/archive/2010/09/06/errors-installing-asp-net-4-0.aspx Except that the proposed solution does not work for me. I have expanded the %windir% macros within isapiCgiRestriction section for .NET 4.0 - and aspnet_regiis still fails for me. Any other ideas?

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• IIS 7.5 + Windows Server 2008 R2 + ASP.NET 4.0 HTTP 500 Error?

  - by Dave

  Hi, I'm having an issue I cannot track down and I have looked through the forums and not found anything that sheds any light. I have a fresh install of a Server 2008 R2 Web that I am trying to load an application I created and tested on a Windows 7 machine running IIS 7.5 using ASP.NET 4.0. Everything works fine on the dev machine. But when I used the Web Deployment tool to move it to the server, I now get a HTTP 500 error without a lot of information: Module AspNetInitClrHostFailureModule Notification BeginRequest Handler StaticFile Error Code 0x80070002 Requested URL http://192.168.1.83:80/ Physical Path C:\JustStreamIt Logon Method Not yet determined Logon User Not yet determined Failed Request Tracing Log Directory C:\inetpub\logs\FailedReqLogFiles And in my trace file I get: view trace Warning -SET_RESPONSE_ERROR_DESCRIPTION ErrorDescription An error message detailing the cause of this specific request failure can be found in the application event log of the web server. Please review this log entry to discover what caused this error to occur. view trace Warning -MODULE_SET_RESPONSE_ERROR_STATUS ModuleName AspNetInitClrHostFailureModule Notification 1 HttpStatus 500 HttpReason Internal Server Error HttpSubStatus 0 ErrorCode 2147942402 ConfigExceptionInfo Notification BEGIN_REQUEST ErrorCode The system cannot find the file specified. (0x80070002) And I get the following in the Application Log: Log Name: Application Source: Microsoft-Windows-IIS-W3SVC-WP Date: 5/28/2010 2:08:10 PM Event ID: 2299 Task Category: None Level: Error Keywords: Classic User: N/A Computer: win-ltfkdo1dnfp Description: An application has reported as being unhealthy. The worker process will now request a recycle. Reason given: An error message detailing the cause of this specific request failure can be found in the application event log of the web server. Please review this log entry to discover what caused this error to occur. . The data is the error. Event Xml: <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event"> <System> <Provider Name="Microsoft-Windows-IIS-W3SVC-WP" Guid="{670080D9-742A-4187-8D16-41143D1290BD}" EventSourceName="W3SVC-WP" /> <EventID Qualifiers="49152">2299</EventID> <Version>0</Version> <Level>2</Level> <Task>0</Task> <Opcode>0</Opcode> <Keywords>0x80000000000000</Keywords> <TimeCreated SystemTime="2010-05-28T21:08:10.000000000Z" /> <EventRecordID>1663</EventRecordID> <Correlation /> <Execution ProcessID="0" ThreadID="0" /> <Channel>Application</Channel> <Computer>win-ltfkdo1dnfp</Computer> <Security /> </System> <EventData> <Data Name="Reason">An error message detailing the cause of this specific request failure can be found in the application event log of the web server. Please review this log entry to discover what caused this error to occur. </Data> <Binary>02000780</Binary> </EventData> </Event> Anyone have a suggestion about where I should start looking?

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• How do you install .net4 on a Server 2008 r2 machine through psremoting in powershell?

  - by Jake

  I need to write a script that installs .net 4 remotely using powershell to a group of Server 2008 R2 machines. I based my script off of http://social.technet.microsoft.com/Forums/en-US/winserverpowershell/thread/3045eb24-7739-4695-ae94-5aa7052119fd/. enter-pssession -computername localhost $arglist = "/q /norestart /log C:\Users\tempuser\Desktop\dotnetfx4" $filepath = "C:\Users\tempuser\Desktop\dotNetFx40_Full_setup.exe" Start-Process -FilePath $filepath -ArgumentList $arglist -Wait -PassThru After running the command I would get the following log errors (running the same lines locally would install .net without error): Action: Downloading Item Failed to CreateJob : hr= 0x80200014 Action: Performing actions on all Items Action: Performing Action on Exe at C:\Users\tempuser\Desktop\dotnetfx4\SetupUtility.exe Exe (C:\Users\tempuser\Desktop\dotnetfx4\SetupUtility.exe) succeeded. Exe Log File: dd_SetupUtility.txt Action complete Action: ServiceControl - Stop clr_optimization_v2.0.50727_32 ServiceControl operation succeeded! Action complete Action: ServiceControl - Stop clr_optimization_v2.0.50727_64 ServiceControl operation succeeded! Action complete Action: Performing Action on Exe at C:\Users\tempuser\AppData\Local\Temp\Microsoft .NET Framework 4 Setup_4.0.30319\Windows6.1-KB958488-v6001-x64.msu Exe (C:\Users\tempuser\AppData\Local\Temp\Microsoft .NET Framework 4 Setup_4.0.30319\Windows6.1-KB958488-v6001-x64.msu) failed with 0x5 - Access is denied. . PerformOperation on exe returned exit code 5 (translates to HRESULT = 0x5) Action complete OnFailureBehavior for this item is to Rollback. Action: Performing actions on all Items Action complete Action complete Action: Downloading http://go.microsoft.com/fwlink/?LinkId=164184&clcid=0x409 using WinHttp WinHttpDetectAutoProxyConfigUrl failed with error: 12180 Unable to retrieve Proxy information although WinHttpGetIEProxyConfigForCurrentUser called succeeded Action complete C:\Users\tempuser\AppData\Local\Temp\Microsoft .NET Framework 4 Setup_4.0.30319\TMPF279.tmp.exe: Verifying signature for netfx_Core.mzz C:\Users\tempuser\AppData\Local\Temp\Microsoft .NET Framework 4 Setup_4.0.30319\TMPF279.tmp.exe Signature verified successfully for netfx_Core.mzz Action complete Decompression completed with code: 16389 Decompression of payload failed: C:\Users\tempuser\AppData\Local\Temp\Microsoft .NET Framework 4 Setup_4.0.30319\netfx_Core.mzz Action complete Final Result: Installation failed with error code: (0x80074005) (Elapsed time: 0 00:00:28). Is there some security setting or perhaps something else I've missed?

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• netsnmp - how to register string?

  - by user1495181

  I use net-snmp. I try to add my own mibs (no need in handler, just a MIB that i can get and set by snmp call), so i followed the scalar example. In order to add my own mibs i defined them in the mib file and create an agent extension.(see below). It work, so i have now an integer MIB. Now i want to add string mib, so i define the MIB , but i dont find a register API for string, like i have for the int - netsnmp_register_int_instance. I look in the includes file , but dosnt found matching one. agent: #include <net-snmp/net-snmp-config.h> #include <net-snmp/net-snmp-includes.h> #include <net-snmp/agent/net-snmp-agent-includes.h> #include "monitor.h" static int int_init = 0; /* default value */ void init_monitor(void) { oid open_connections_count_oid[] = { 1, 3, 6, 1, 4, 1, 8075, 1, 0 }; netsnmp_register_int_instance("open_connections_count", open_connections_count_oid, OID_LENGTH(open_connections_count_oid), &int_init, NULL); }

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• Why won't IIS serve my website? - 404 Page Not Found

  - by Giffyguy

  Built a brand new server, with a fresh copy of Windows Server 2003 Enterprise x86 Edition. Installed the .NET Framework 1.1, 2.0, 3.5, and 4.0 Added the "Domain Controller" and "Application Server" roles. Created a new website, pointed it to a local directory: C:\Inetpub\angryoctopus.net\ Added the appropriate headers: angryoctopus.net, www.angryoctopus.net, TCP port 80, all IPs Moved the website content into the local directory. Configured the default document in IIS: Default.aspx Enabled ASP.NET for this website, and set it to the correct version: 2.0.50727 Configured the zone angryoctopus.net in DNS. Tested DNS lookup here to ensure DNS was functional. Opened website in VS 2008 and re-built (and debugged) to ensure the content was functional. I can clearly see that IIS is responding normally, by browsing directly to my server's IP address. Since this does not use the angryoctopus HTTP header, the default website is displayed instead: the "Under Construction" page. And yet, after all of this, angryoctopus.net still returns 404. Does anybody know what could be wrong? What troubleshooting steps have I forgotten? Is there a command-line diagnostic that might provide more information?

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• Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 3 – Table per Concrete Type (TPC) and Choosing Strategy Guidelines

  - by mortezam

  This is the third (and last) post in a series that explains different approaches to map an inheritance hierarchy with EF Code First. I've described these strategies in previous posts: Part 1 – Table per Hierarchy (TPH) Part 2 – Table per Type (TPT)In today’s blog post I am going to discuss Table per Concrete Type (TPC) which completes the inheritance mapping strategies supported by EF Code First. At the end of this post I will provide some guidelines to choose an inheritance strategy mainly based on what we've learned in this series. TPC and Entity Framework in the Past Table per Concrete type is somehow the simplest approach suggested, yet using TPC with EF is one of those concepts that has not been covered very well so far and I've seen in some resources that it was even discouraged. The reason for that is just because Entity Data Model Designer in VS2010 doesn't support TPC (even though the EF runtime does). That basically means if you are following EF's Database-First or Model-First approaches then configuring TPC requires manually writing XML in the EDMX file which is not considered to be a fun practice. Well, no more. You'll see that with Code First, creating TPC is perfectly possible with fluent API just like other strategies and you don't need to avoid TPC due to the lack of designer support as you would probably do in other EF approaches. Table per Concrete Type (TPC)In Table per Concrete type (aka Table per Concrete class) we use exactly one table for each (nonabstract) class. All properties of a class, including inherited properties, can be mapped to columns of this table, as shown in the following figure: As you can see, the SQL schema is not aware of the inheritance; effectively, we’ve mapped two unrelated tables to a more expressive class structure. If the base class was concrete, then an additional table would be needed to hold instances of that class. I have to emphasize that there is no relationship between the database tables, except for the fact that they share some similar columns. TPC Implementation in Code First Just like the TPT implementation, we need to specify a separate table for each of the subclasses. We also need to tell Code First that we want all of the inherited properties to be mapped as part of this table. In CTP5, there is a new helper method on EntityMappingConfiguration class called MapInheritedProperties that exactly does this for us. Here is the complete object model as well as the fluent API to create a TPC mapping: public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } }          public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } }          public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } }      public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; }              protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<BankAccount>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("BankAccounts");         });         modelBuilder.Entity<CreditCard>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("CreditCards");         });                 } } The Importance of EntityMappingConfiguration ClassAs a side note, it worth mentioning that EntityMappingConfiguration class turns out to be a key type for inheritance mapping in Code First. Here is an snapshot of this class: namespace System.Data.Entity.ModelConfiguration.Configuration.Mapping {     public class EntityMappingConfiguration<TEntityType> where TEntityType : class     {         public ValueConditionConfiguration Requires(string discriminator);         public void ToTable(string tableName);         public void MapInheritedProperties();     } } As you have seen so far, we used its Requires method to customize TPH. We also used its ToTable method to create a TPT and now we are using its MapInheritedProperties along with ToTable method to create our TPC mapping. TPC Configuration is Not Done Yet!We are not quite done with our TPC configuration and there is more into this story even though the fluent API we saw perfectly created a TPC mapping for us in the database. To see why, let's start working with our object model. For example, the following code creates two new objects of BankAccount and CreditCard types and tries to add them to the database: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount();     CreditCard creditCard = new CreditCard() { CardType = 1 };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Running this code throws an InvalidOperationException with this message: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. The reason we got this exception is because DbContext.SaveChanges() internally invokes SaveChanges method of its internal ObjectContext. ObjectContext's SaveChanges method on its turn by default calls AcceptAllChanges after it has performed the database modifications. AcceptAllChanges method merely iterates over all entries in ObjectStateManager and invokes AcceptChanges on each of them. Since the entities are in Added state, AcceptChanges method replaces their temporary EntityKey with a regular EntityKey based on the primary key values (i.e. BillingDetailId) that come back from the database and that's where the problem occurs since both the entities have been assigned the same value for their primary key by the database (i.e. on both BillingDetailId = 1) and the problem is that ObjectStateManager cannot track objects of the same type (i.e. BillingDetail) with the same EntityKey value hence it throws. If you take a closer look at the TPC's SQL schema above, you'll see why the database generated the same values for the primary keys: the BillingDetailId column in both BankAccounts and CreditCards table has been marked as identity. How to Solve The Identity Problem in TPC As you saw, using SQL Server’s int identity columns doesn't work very well together with TPC since there will be duplicate entity keys when inserting in subclasses tables with all having the same identity seed. Therefore, to solve this, either a spread seed (where each table has its own initial seed value) will be needed, or a mechanism other than SQL Server’s int identity should be used. Some other RDBMSes have other mechanisms allowing a sequence (identity) to be shared by multiple tables, and something similar can be achieved with GUID keys in SQL Server. While using GUID keys, or int identity keys with different starting seeds will solve the problem but yet another solution would be to completely switch off identity on the primary key property. As a result, we need to take the responsibility of providing unique keys when inserting records to the database. We will go with this solution since it works regardless of which database engine is used. Switching Off Identity in Code First We can switch off identity simply by placing DatabaseGenerated attribute on the primary key property and pass DatabaseGenerationOption.None to its constructor. DatabaseGenerated attribute is a new data annotation which has been added to System.ComponentModel.DataAnnotations namespace in CTP5: public abstract class BillingDetail {     [DatabaseGenerated(DatabaseGenerationOption.None)]     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } As always, we can achieve the same result by using fluent API, if you prefer that: modelBuilder.Entity<BillingDetail>()             .Property(p => p.BillingDetailId)             .HasDatabaseGenerationOption(DatabaseGenerationOption.None); Working With The Object Model Our TPC mapping is ready and we can try adding new records to the database. But, like I said, now we need to take care of providing unique keys when creating new objects: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount()      {          BillingDetailId = 1                          };     CreditCard creditCard = new CreditCard()      {          BillingDetailId = 2,         CardType = 1     };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Polymorphic Associations with TPC is Problematic The main problem with this approach is that it doesn’t support Polymorphic Associations very well. After all, in the database, associations are represented as foreign key relationships and in TPC, the subclasses are all mapped to different tables so a polymorphic association to their base class (abstract BillingDetail in our example) cannot be represented as a simple foreign key relationship. For example, consider the the domain model we introduced here where User has a polymorphic association with BillingDetail. This would be problematic in our TPC Schema, because if User has a many-to-one relationship with BillingDetail, the Users table would need a single foreign key column, which would have to refer both concrete subclass tables. This isn’t possible with regular foreign key constraints. Schema Evolution with TPC is Complex A further conceptual problem with this mapping strategy is that several different columns, of different tables, share exactly the same semantics. This makes schema evolution more complex. For example, a change to a base class property results in changes to multiple columns. It also makes it much more difficult to implement database integrity constraints that apply to all subclasses. Generated SQLLet's examine SQL output for polymorphic queries in TPC mapping. For example, consider this polymorphic query for all BillingDetails and the resulting SQL statements that being executed in the database: var query = from b in context.BillingDetails select b; Just like the SQL query generated by TPT mapping, the CASE statements that you see in the beginning of the query is merely to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type). TPC's SQL Queries are Union Based As you can see in the above screenshot, the first SELECT uses a FROM-clause subquery (which is selected with a red rectangle) to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 0 and 1) is inserted into the intermediate result; (look at the lines highlighted in yellow.) EF reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined, project over the same columns; hence, EF has to pad and fill up nonexistent columns with NULL. This query will really perform well since here we can let the database optimizer find the best execution plan to combine rows from several tables. There is also no Joins involved so it has a better performance than the SQL queries generated by TPT where a Join is required between the base and subclasses tables. Choosing Strategy GuidelinesBefore we get into this discussion, I want to emphasize that there is no one single "best strategy fits all scenarios" exists. As you saw, each of the approaches have their own advantages and drawbacks. Here are some rules of thumb to identify the best strategy in a particular scenario: If you don’t require polymorphic associations or queries, lean toward TPC—in other words, if you never or rarely query for BillingDetails and you have no class that has an association to BillingDetail base class. I recommend TPC (only) for the top level of your class hierarchy, where polymorphism isn’t usually required, and when modification of the base class in the future is unlikely. If you do require polymorphic associations or queries, and subclasses declare relatively few properties (particularly if the main difference between subclasses is in their behavior), lean toward TPH. Your goal is to minimize the number of nullable columns and to convince yourself (and your DBA) that a denormalized schema won’t create problems in the long run. If you do require polymorphic associations or queries, and subclasses declare many properties (subclasses differ mainly by the data they hold), lean toward TPT. Or, depending on the width and depth of your inheritance hierarchy and the possible cost of joins versus unions, use TPC. By default, choose TPH only for simple problems. For more complex cases (or when you’re overruled by a data modeler insisting on the importance of nullability constraints and normalization), you should consider the TPT strategy. But at that point, ask yourself whether it may not be better to remodel inheritance as delegation in the object model (delegation is a way of making composition as powerful for reuse as inheritance). Complex inheritance is often best avoided for all sorts of reasons unrelated to persistence or ORM. EF acts as a buffer between the domain and relational models, but that doesn’t mean you can ignore persistence concerns when designing your classes. SummaryIn this series, we focused on one of the main structural aspect of the object/relational paradigm mismatch which is inheritance and discussed how EF solve this problem as an ORM solution. We learned about the three well-known inheritance mapping strategies and their implementations in EF Code First. Hopefully it gives you a better insight about the mapping of inheritance hierarchies as well as choosing the best strategy for your particular scenario. Happy New Year and Happy Code-Firsting! References ADO.NET team blog Java Persistence with Hibernate book a { color: #5A99FF; } a:visited { color: #5A99FF; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } .exception { background-color: #f0f0f0; font-style: italic; padding-bottom: 5px; padding-left: 5px; padding-top: 5px; padding-right: 5px; }

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• jQuery Templates - {Supported Tags}

  - by hajan

  I have started with Introduction to jQuery Templates, then jQuery Templates - tmpl(), template() and tmplItem() functions. In this blog we will see what supported tags are available in the jQuery Templates plugin.Template tags can be used inside template together in combination with HTML tags and plain text, which helps to iterate over JSON data. Up to now, there are several supported tags in jQuery Templates plugin: ${expr} or {{= expr}} {{each itemArray}} … {{/each}} {{if condition}} … {{else}} … {{/if}} {{html …}} {{tmpl …}} {{wrap …}} … {{/wrap}}   - ${expr} or {{= expr}} Is used for insertion of data values in the rendered template. It can evaluate fields, functions or expression. Example: <script id="attendeesTemplate" type="text/html">     <li> ${Name} {{= Surname}} </li>         </script> Either ${Name} or {{= Surname}} (with blank space between =<blankspace>Field) will work.   - {{each itemArray}} … {{/each}} each is everywhere the same "(for)each", used to loop over array or collection Example: <script id="attendeesTemplate" type="text/html">     <li>         ${Name} ${Surname}         {{if speaker}}             (<font color="red">speaks</font>)         {{else}}             (attendee)         {{/if}}                 {{each phones}}                             <br />             ${$index}: <em>${$value}</em>         {{/each}}             </li> </script> So, you see we can use ${$index} and ${$value} to get the current index and value while iterating over the item collection. Alternatively, you can add index,value on the following way: {{each(i,v) phones}}     <br />     ${i}: <em>${v}</em> {{/each}} Result would be: Here is complete working example that you can run and see the result: <html xmlns="http://www.w3.org/1999/xhtml" > <head id="Head1" runat="server">     <title>Nesting and Looping Example :: jQuery Templates</title>     <script src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.4.4.min.js" type="text/javascript"></script>     <script src="http://ajax.aspnetcdn.com/ajax/jquery.templates/beta1/jquery.tmpl.js" type="text/javascript"></script>     <script language="javascript" type="text/javascript">         $(function () {             var attendees = [                 { Name: "Hajan", Surname: "Selmani", speaker: true, phones:[070555555, 071888999, 071222333] },                 { Name: "Someone", Surname: "Surname", phones: [070555555, 071222333] },                 { Name: "Third", Surname: "Thirdsurname", phones: [070555555, 071888999, 071222333] },             ];             $("#attendeesTemplate").tmpl(attendees).appendTo("#attendeesList");         });     </script>     <script id="attendeesTemplate" type="text/html">         <li>             ${Name} ${Surname}             {{if speaker}}                 (<font color="red">speaks</font>)             {{else}}                 (attendee)             {{/if}}                     {{each(i,v) phones}}                 <br />                 ${i}: <em>${v}</em>             {{/each}}                 </li>     </script> </head> <body>     <ol id="attendeesList"></ol>     </body> </html>   - {{if condition}} … {{else}} … {{/if}} Standard if/else statement. Of course, you can use it without the {{else}} if you have such condition to check, however closing the {{/if}} tag is required. Example: {{if speaker}}     (<font color="red">speaks</font>) {{else}}     (attendee) {{/if}} You have this same code block in the above complete example showing the 'each' cycle ;).   - {{html …}} Is used for insertion of HTML markup strings in the rendered template. Evaluates the specified field on the current data item, or the specified JavaScript function or expression. Example: - without {{html …}} <script language="javascript" type="text/javascript">   $(function () {   var attendees = [             { Name: "Hajan", Surname: "Selmani", Info: "He <font color='red'>is the speaker of today's</font> session", speaker: true },         ];   $("#myTemplate").tmpl(attendees).appendTo("#speakers"); }); </script> <script id="myTemplate" type="text/html">     ${Name} ${Surname} <br />     ${Info} </script> Result: - with {{html …}} <script language="javascript" type="text/javascript">   $(function () {   var attendees = [             { Name: "Hajan", Surname: "Selmani", Info: "He <font color='red'>is the speaker of today's</font> session", speaker: true },         ];   $("#myTemplate").tmpl(attendees).appendTo("#speakers"); }); </script> <script id="myTemplate" type="text/html">     ${Name} ${Surname} <br />     {{html Info}} </script> Result:   - {{wrap …}} It’s used for composition and incorporation of wrapped HTML. It’s similar to {{tmpl}} Example: <script id="myTmpl" type="text/html">     <div id="personInfo">     <br />     ${Name} ${Surname}     {{wrap "#myWrapper"}}         <h2>${Info}</h2>         <div>             {{if speaker}}                 (speaker)             {{else}}                 (attendee)             {{/if}}         </div>     {{/wrap}}     </div> </script> <script id="myWrapper" type="text/html">     <table><tbody>         <tr>             {{each $item.html("div")}}                 <td>                     {{html $value}}                 </td>             {{/each}}         </tr>     </tbody></table> </script> All the HTMl content inside the {{wrap}} … {{/wrap}} is available to the $item.html(filter, textOnly) method. In our example, we have defined some standard template and created wrapper which calls the other template with id myWrapper. Then using $item.html(“div”) we find the div tag and render the html value (together with the div tag) inside the <td> … </td>. So, here inside td the <div> <speaker or attendee depending of the condition> </div>  will be rendered. The HTML output from this is:   - {{tmpl …}} Used for composition as template items Example: <script id="myTemplate" type="text/html">     <div id="bookItem">         <div id="bookCover">             {{tmpl "#bookCoverTemplate"}}         </div>         <div id="bookDetails">             <div id="book">                             ${title} - ${author}             </div>             <div id="price">$${price}</div>             <div id="Details">${pages} pgs. - ${year} year</div>         </div>     </div> </script> <script id="bookCoverTemplate" type="text/html">     <img src="${image}" alt="${title} Image" /> </script> In this example, using {{tmpl “#bookCoverTemplate”}} I’m calling another template inside the first template. In the other template I’ve created template for a book cover. The rendered HTML of this is: and   So we have seen example for each of the tags that are right now available in the jQuery Templates (beta) plugin which is created by Microsoft as a contribution to the open source jQuery Project. I hope this was useful blog post for you. Regards, HajanNEXT - jQuery Templates with ASP.NET MVC

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• Change the default Icon on your jQuery UI Accordion

  - by hajan

  I've got this question in one of my previous blogs posted here (the same blog is posted on codeasp.net too), dealing with jQuery UI Accordion and I thought it's nice to recap this in a blog post so that I will have it documented for further reference. In the previous blog, I'm creating tabs content navigation using jQuery UI Accordion. So, it's quite simple code and all I do there is calling accordion() function. <script language="javascript" type="text/javascript">     $(function() {         $("#products").accordion();     }); </script> The default image icons for each item is the arrow. The accordion uses the right arrow and down arrow images. So, what we should do in order to change them? JQuery UI Accordion contains option with name icons that has header and headerSelected properties. We can override them with either the existing classes from jQuery UI themes or with our own. 1. Using existing jQuery UI Theme classes - Open the follownig link: http://jqueryui.com/themeroller/#icons You will see the icons available in the jQuery UI theme. Mouse over on each icon and you will see the class name for each icon. As you can see, each icon has class name constructed in the following way: ui-icon-<name> All icons in one image - In our example, I will use ui-icon-circle-plus  and ui-icon-circle-minus (plus and minus icons). - Lets set the icons <script language="javascript" type="text/javascript">     $(function() {         //initialize accordion                 $("#products").accordion();         //set accordion header options         $("#products").accordion("option", "icons",         { 'header': 'ui-icon-circle-plus', 'headerSelected': 'ui-icon-circle-minus' });     }); </script> From the code above, you can see that I first intialize the accordion plugin, and after I override the default icons with the ui-icon-circle-plyus for header and ui-icon-circle-minus for headerSelected. Here is the end result: So, now you see we have the plus/minus circle icons for the default header state and the selected header state.   2. Add my own icons - If you want to add your own icons, you can do that by creating your own custom css classes. - Lets create classes for both, the header default state and header selected state <style type="text/css">     .defaultIcon     {         background-image: url(images/icons/defaultIcon.png) !important;         width: 25px;         height: 25px;     }     .selectedIcon     {         background-image: url(images/icons/selectedIcon.png) !important;         width: 25px;         height: 25px;     } </style> As you can see, I use my own images placed in images/icons/ folder - default icon - selected icon One very important thing to note here is the !important key added on each background-image property. It's like that in order to give highest importancy to our image so that the default jQuery UI theme icon images will have less importancy and won't be used. And the jQuery code is: <script language="javascript" type="text/javascript">     $(function() {         //initialize accordion                 $("#products").accordion();         //set accordion header options         $("#products").accordion("option", "icons",         { 'header': 'defaultIcon', 'headerSelected': 'selectedIcon' });     }); </script> Note: For both #1 and #2 cases, we use the class names without adding . (dot) at the beginning of the name (as we do with selectors). That's because the the header and headerSelected properties accept classes only as a value, so the rest is done by the plugin itself. The complete code with my own custom images is: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head id="Head1" runat="server">     <title>jQuery Accordion</title>     <link type="text/css" href="http://ajax.microsoft.com/ajax/jquery.ui/1.8.5/themes/blitzer/jquery-ui.css"         rel="Stylesheet" />     <style type="text/css">         .defaultIcon         {             background-image: url(images/icons/defaultIcon.png) !important;             width: 25px;             height: 25px;         }         .selectedIcon         {             background-image: url(images/icons/selectedIcon.png) !important;             width: 25px;             height: 25px;         }     </style>     <script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery/jquery-1.4.4.js"></script>     <script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery.ui/1.8.6/jquery-ui.js"></script>     <script language="javascript" type="text/javascript">         $(function() {             //initialize accordion                         $("#products").accordion();             //set accordion header options             $("#products").accordion("option", "icons",             { 'header': 'defaultIcon', 'headerSelected': 'selectedIcon' });         });             </script> </head> <body>     <form id="form1" runat="server">     <div id="products" style="width: 500px;">         <h3>             <a href="#">                 Product 1</a></h3>         <div>             <p>                 Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus in tortor metus,                 a aliquam dui. Mauris euismod lorem eget nulla semper semper. Vestibulum pretium                 rhoncus cursus. Vestibulum rhoncus, magna sit amet fermentum fringilla, nunc nisl                 pellentesque libero, nec commodo libero ipsum a tellus. Maecenas sed varius est.                 Sed vel risus at nisi imperdiet sollicitudin eget ac orci. Duis ac tristique sem.             </p>         </div>         <h3>             <a href="#">                 Product 2</a></h3>         <div>             <p>                 Aliquam pretium scelerisque nisl in malesuada. Proin dictum elementum rutrum. Etiam                 eleifend massa id dui porta tincidunt. Integer sodales nisi nec ligula lacinia tincidunt                 vel in purus. Mauris ultrices velit quis massa dignissim rhoncus. Proin posuere                 convallis euismod. Vestibulum convallis sagittis arcu id faucibus.             </p>         </div>         <h3>             <a href="#">                 Product 3</a></h3>         <div>             <p>                 Quisque quis magna id nibh laoreet condimentum a sed nisl. In hac habitasse platea                 dictumst. Proin sem eros, dignissim sed consequat sit amet, interdum id ante. Ut                 id nisi in ante fermentum accumsan vitae ut est. Morbi tellus enim, convallis ac                 rutrum a, condimentum ut turpis. Proin sit amet pretium felis.             </p>             <ul>                 <li>List item one</li>                 <li>List item two</li>                 <li>List item three</li>             </ul>         </div>     </div>     </form> </body> </html> The end result is: Hope this was helpful. Regards,Hajan

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• A ToDynamic() Extension Method For Fluent Reflection

  - by Dixin

  Recently I needed to demonstrate some code with reflection, but I felt it inconvenient and tedious. To simplify the reflection coding, I created a ToDynamic() extension method. The source code can be downloaded from here. Problem One example for complex reflection is in LINQ to SQL. The DataContext class has a property Privider, and this Provider has an Execute() method, which executes the query expression and returns the result. Assume this Execute() needs to be invoked to query SQL Server database, then the following code will be expected: using (NorthwindDataContext database = new NorthwindDataContext()) { // Constructs the query. IQueryable<Product> query = database.Products.Where(product => product.ProductID > 0) .OrderBy(product => product.ProductName) .Take(2); // Executes the query. Here reflection is required, // because Provider, Execute(), and ReturnValue are not public members. IEnumerable<Product> results = database.Provider.Execute(query.Expression).ReturnValue; // Processes the results. foreach (Product product in results) { Console.WriteLine("{0}, {1}", product.ProductID, product.ProductName); } } Of course, this code cannot compile. And, no one wants to write code like this. Again, this is just an example of complex reflection. using (NorthwindDataContext database = new NorthwindDataContext()) { // Constructs the query. IQueryable<Product> query = database.Products.Where(product => product.ProductID > 0) .OrderBy(product => product.ProductName) .Take(2); // database.Provider PropertyInfo providerProperty = database.GetType().GetProperty( "Provider", BindingFlags.NonPublic | BindingFlags.GetProperty | BindingFlags.Instance); object provider = providerProperty.GetValue(database, null); // database.Provider.Execute(query.Expression) // Here GetMethod() cannot be directly used, // because Execute() is a explicitly implemented interface method. Assembly assembly = Assembly.Load("System.Data.Linq"); Type providerType = assembly.GetTypes().SingleOrDefault( type => type.FullName == "System.Data.Linq.Provider.IProvider"); InterfaceMapping mapping = provider.GetType().GetInterfaceMap(providerType); MethodInfo executeMethod = mapping.InterfaceMethods.Single(method => method.Name == "Execute"); IExecuteResult executeResult = executeMethod.Invoke(provider, new object[] { query.Expression }) as IExecuteResult; // database.Provider.Execute(query.Expression).ReturnValue IEnumerable<Product> results = executeResult.ReturnValue as IEnumerable<Product>; // Processes the results. foreach (Product product in results) { Console.WriteLine("{0}, {1}", product.ProductID, product.ProductName); } } This may be not straight forward enough. So here a solution will implement fluent reflection with a ToDynamic() extension method: IEnumerable<Product> results = database.ToDynamic() // Starts fluent reflection. .Provider.Execute(query.Expression).ReturnValue; C# 4.0 dynamic In this kind of scenarios, it is easy to have dynamic in mind, which enables developer to write whatever code after a dot: using (NorthwindDataContext database = new NorthwindDataContext()) { // Constructs the query. IQueryable<Product> query = database.Products.Where(product => product.ProductID > 0) .OrderBy(product => product.ProductName) .Take(2); // database.Provider dynamic dynamicDatabase = database; dynamic results = dynamicDatabase.Provider.Execute(query).ReturnValue; } This throws a RuntimeBinderException at runtime: 'System.Data.Linq.DataContext.Provider' is inaccessible due to its protection level. Here dynamic is able find the specified member. So the next thing is just writing some custom code to access the found member. .NET 4.0 DynamicObject, and DynamicWrapper<T> Where to put the custom code for dynamic? The answer is DynamicObject’s derived class. I first heard of DynamicObject from Anders Hejlsberg's video in PDC2008. It is very powerful, providing useful virtual methods to be overridden, like: TryGetMember() TrySetMember() TryInvokeMember() etc.  (In 2008 they are called GetMember, SetMember, etc., with different signature.) For example, if dynamicDatabase is a DynamicObject, then the following code: dynamicDatabase.Provider will invoke dynamicDatabase.TryGetMember() to do the actual work, where custom code can be put into. Now create a type to inherit DynamicObject: public class DynamicWrapper<T> : DynamicObject { private readonly bool _isValueType; private readonly Type _type; private T _value; // Not readonly, for value type scenarios. public DynamicWrapper(ref T value) // Uses ref in case of value type. { if (value == null) { throw new ArgumentNullException("value"); } this._value = value; this._type = value.GetType(); this._isValueType = this._type.IsValueType; } public override bool TryGetMember(GetMemberBinder binder, out object result) { // Searches in current type's public and non-public properties. PropertyInfo property = this._type.GetTypeProperty(binder.Name); if (property != null) { result = property.GetValue(this._value, null).ToDynamic(); return true; } // Searches in explicitly implemented properties for interface. MethodInfo method = this._type.GetInterfaceMethod(string.Concat("get_", binder.Name), null); if (method != null) { result = method.Invoke(this._value, null).ToDynamic(); return true; } // Searches in current type's public and non-public fields. FieldInfo field = this._type.GetTypeField(binder.Name); if (field != null) { result = field.GetValue(this._value).ToDynamic(); return true; } // Searches in base type's public and non-public properties. property = this._type.GetBaseProperty(binder.Name); if (property != null) { result = property.GetValue(this._value, null).ToDynamic(); return true; } // Searches in base type's public and non-public fields. field = this._type.GetBaseField(binder.Name); if (field != null) { result = field.GetValue(this._value).ToDynamic(); return true; } // The specified member is not found. result = null; return false; } // Other overridden methods are not listed. } In the above code, GetTypeProperty(), GetInterfaceMethod(), GetTypeField(), GetBaseProperty(), and GetBaseField() are extension methods for Type class. For example: internal static class TypeExtensions { internal static FieldInfo GetBaseField(this Type type, string name) { Type @base = type.BaseType; if (@base == null) { return null; } return @base.GetTypeField(name) ?? @base.GetBaseField(name); } internal static PropertyInfo GetBaseProperty(this Type type, string name) { Type @base = type.BaseType; if (@base == null) { return null; } return @base.GetTypeProperty(name) ?? @base.GetBaseProperty(name); } internal static MethodInfo GetInterfaceMethod(this Type type, string name, params object[] args) { return type.GetInterfaces().Select(type.GetInterfaceMap).SelectMany(mapping => mapping.TargetMethods) .FirstOrDefault( method => method.Name.Split('.').Last().Equals(name, StringComparison.Ordinal) && method.GetParameters().Count() == args.Length && method.GetParameters().Select( (parameter, index) => parameter.ParameterType.IsAssignableFrom(args[index].GetType())).Aggregate( true, (a, b) => a && b)); } internal static FieldInfo GetTypeField(this Type type, string name) { return type.GetFields( BindingFlags.GetField | BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic).FirstOrDefault( field => field.Name.Equals(name, StringComparison.Ordinal)); } internal static PropertyInfo GetTypeProperty(this Type type, string name) { return type.GetProperties( BindingFlags.GetProperty | BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic).FirstOrDefault( property => property.Name.Equals(name, StringComparison.Ordinal)); } // Other extension methods are not listed. } So now, when invoked, TryGetMember() searches the specified member and invoke it. The code can be written like this: dynamic dynamicDatabase = new DynamicWrapper<NorthwindDataContext>(ref database); dynamic dynamicReturnValue = dynamicDatabase.Provider.Execute(query.Expression).ReturnValue; This greatly simplified reflection. ToDynamic() and fluent reflection To make it even more straight forward, A ToDynamic() method is provided: public static class DynamicWrapperExtensions { public static dynamic ToDynamic<T>(this T value) { return new DynamicWrapper<T>(ref value); } } and a ToStatic() method is provided to unwrap the value: public class DynamicWrapper<T> : DynamicObject { public T ToStatic() { return this._value; } } In the above TryGetMember() method, please notice it does not output the member’s value, but output a wrapped member value (that is, memberValue.ToDynamic()). This is very important to make the reflection fluent. Now the code becomes: IEnumerable<Product> results = database.ToDynamic() // Here starts fluent reflection. .Provider.Execute(query.Expression).ReturnValue .ToStatic(); // Unwraps to get the static value. With the help of TryConvert(): public class DynamicWrapper<T> : DynamicObject { public override bool TryConvert(ConvertBinder binder, out object result) { result = this._value; return true; } } ToStatic() can be omitted: IEnumerable<Product> results = database.ToDynamic() .Provider.Execute(query.Expression).ReturnValue; // Automatically converts to expected static value. Take a look at the reflection code at the beginning of this post again. Now it is much much simplified! Special scenarios In 90% of the scenarios ToDynamic() is enough. But there are some special scenarios. Access static members Using extension method ToDynamic() for accessing static members does not make sense. Instead, DynamicWrapper<T> has a parameterless constructor to handle these scenarios: public class DynamicWrapper<T> : DynamicObject { public DynamicWrapper() // For static. { this._type = typeof(T); this._isValueType = this._type.IsValueType; } } The reflection code should be like this: dynamic wrapper = new DynamicWrapper<StaticClass>(); int value = wrapper._value; int result = wrapper.PrivateMethod(); So accessing static member is also simple, and fluent of course. Change instances of value types Value type is much more complex. The main problem is, value type is copied when passing to a method as a parameter. This is why ref keyword is used for the constructor. That is, if a value type instance is passed to DynamicWrapper<T>, the instance itself will be stored in this._value of DynamicWrapper<T>. Without the ref keyword, when this._value is changed, the value type instance itself does not change. Consider FieldInfo.SetValue(). In the value type scenarios, invoking FieldInfo.SetValue(this._value, value) does not change this._value, because it changes the copy of this._value. I searched the Web and found a solution for setting the value of field: internal static class FieldInfoExtensions { internal static void SetValue<T>(this FieldInfo field, ref T obj, object value) { if (typeof(T).IsValueType) { field.SetValueDirect(__makeref(obj), value); // For value type. } else { field.SetValue(obj, value); // For reference type. } } } Here __makeref is a undocumented keyword of C#. But method invocation has problem. This is the source code of TryInvokeMember(): public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, out object result) { if (binder == null) { throw new ArgumentNullException("binder"); } MethodInfo method = this._type.GetTypeMethod(binder.Name, args) ?? this._type.GetInterfaceMethod(binder.Name, args) ?? this._type.GetBaseMethod(binder.Name, args); if (method != null) { // Oops! // If the returnValue is a struct, it is copied to heap. object resultValue = method.Invoke(this._value, args); // And result is a wrapper of that copied struct. result = new DynamicWrapper<object>(ref resultValue); return true; } result = null; return false; } If the returned value is of value type, it will definitely copied, because MethodInfo.Invoke() does return object. If changing the value of the result, the copied struct is changed instead of the original struct. And so is the property and index accessing. They are both actually method invocation. For less confusion, setting property and index are not allowed on struct. Conclusions The DynamicWrapper<T> provides a simplified solution for reflection programming. It works for normal classes (reference types), accessing both instance and static members. In most of the scenarios, just remember to invoke ToDynamic() method, and access whatever you want: StaticType result = someValue.ToDynamic()._field.Method().Property[index]; In some special scenarios which requires changing the value of a struct (value type), this DynamicWrapper<T> does not work perfectly. Only changing struct’s field value is supported. The source code can be downloaded from here, including a few unit test code.

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• AWS .NET SDK v2: setting up queues and topics

  - by Elton Stoneman

  Originally posted on: http://geekswithblogs.net/EltonStoneman/archive/2013/10/13/aws-.net-sdk-v2-setting-up-queues-and-topics.aspxFollowing on from my last post, reading from SQS queues with the new SDK is easy stuff, but linking a Simple Notification Service topic to an SQS queue is a bit more involved. The AWS model for topics and subscriptions is a bit more advanced than in Azure Service Bus. SNS lets you have subscribers on multiple different channels, so you can send a message which gets relayed to email address, mobile apps and SQS queues all in one go. As the topic owner, when you request a subscription on any channel, the owner needs to confirm they’re happy for you to send them messages. With email subscriptions, the user gets a confirmation request from Amazon which they need to reply to before they start getting messages. With SQS, you need to grant the topic permission to write to the queue. If you own both the topic and the queue, you can do it all in code with the .NET SDK. Let’s say you want to create a new topic, a new queue as a topic subscriber, and link the two together. Creating the topic is easy with the SNS client (which has an expanded name, AmazonSimpleNotificationServiceClient, compare to the SQS class which is just called QueueClient): var request = new CreateTopicRequest(); request.Name = TopicName; var response = _snsClient.CreateTopic(request); TopicArn = response.TopicArn; In the response from AWS (which I’m assuming is successful), you get an ARN – Amazon Resource Name – which is the unique identifier for the topic. We create the queue using the same code from my last post, AWS .NET SDK v2: the message-pump pattern, and then we need to subscribe the queue to the topic. The topic creates the subscription request: var response = _snsClient.Subscribe(new SubscribeRequest { TopicArn = TopicArn, Protocol = "sqs", Endpoint = _queueClient.QueueArn }); That response will give you an ARN for the subscription, which you’ll need if you want to set attributes like RawMessageDelivery. Then the SQS client needs to confirm the subscription by allowing the topic to send messages to it. The SDK doesn’t give you a nice mechanism for doing that, so I’ve extended my AWS wrapper with a method that encapsulates it: internal void AllowSnsToSendMessages(TopicClient topicClient) { var policy = Policies.AllowSendFormat.Replace("%QueueArn%", QueueArn).Replace("%TopicArn%", topicClient.TopicArn); var request = new SetQueueAttributesRequest(); request.Attributes.Add("Policy", policy); request.QueueUrl = QueueUrl; var response = _sqsClient.SetQueueAttributes(request); } That builds up a policy statement, which gets added to the queue as an attribute, and specifies that the topic is allowed to send messages to the queue. The statement itself is a JSON block which contains the ARN of the queue, the ARN of the topic, and an Allow effect for the sqs:SendMessage action: public const string AllowSendFormat= @"{ ""Statement"": [ { ""Sid"": ""MySQSPolicy001"", ""Effect"": ""Allow"", ""Principal"": { ""AWS"": ""*"" }, ""Action"": ""sqs:SendMessage"", ""Resource"": ""%QueueArn%"", ""Condition"": { ""ArnEquals"": { ""aws:SourceArn"": ""%TopicArn%"" } } } ] }"; There’s a new gist with an updated QueueClient and a new TopicClient here: Wrappers for the SQS and SNS clients in the AWS SDK for .NET v2. Both clients have an Ensure() method which creates the resource, so if you want to create a topic and a subscription you can use:  var topicClient = new TopicClient(“BigNews”, “ImListening”); And the topic client has a Subscribe() method, which calls into the message pump on the queue client: topicClient.Subscribe(x=>Log.Debug(x.Body)); var message = {}; //etc. topicClient.Publish(message); So you can isolate all the fiddly bits and use SQS and SNS with a similar interface to the Azure SDK.

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• Development Quirk From ASP.NET Dynamic Compilation

  - by jkauffman

  The Problem I got a compilation error in my ASP.NET MVC3 project that tested my sanity today. (As always, names are changed to protect the innocent) The type or namespace name 'FishViewModel' does not exist in the namespace 'Company.Product.Application.Models' (are you missing an assembly reference?) Sure looks easy! There must be something in the project referring to a FishViewModel. The Confusing Part The first thing I noticed was the that error was occuring in a folder clearly not in my project and in files that I definitely had not created: %SystemRoot%\Microsoft.NET\Framework\(versionNumber)\Temporary ASP.NET Files\ App_Web_mezpfjae.1.cs I also ascertained these facts, each of which made me more confused than the last: Rebuild and Clean had no effect. No controllers in the project ever returned a ViewResult using FishViewModel. No views in the project defined that they use FishViewModel. Searching across all files included in the project for “FishViewModel” provided no results. The build server did not report a problem. The Solution The problem stemmed from a file that was not included in the project but still present on the file system: (By the way, if you don’t know this trick already, there is a toolbar button in the Solution Explorer window to “Show All Files” which allows you to see files all files in the file system) In my situation, I was working on the mission-critical Fish view before abandoning the feature. Instead of deleting the file, I excluded it from the project. However, this was a bad move. It caused the build failure, and in order to fix the error, this file must be deleted. By the way, this file was not in source control, so the build server did not have it. This explains why my build server did not report a problem for me. The Explanation So, what’s going on? This file isn’t even a part of the project, so why is it failing the build? This is a behavior of the ASP.NET Dynamic Compilation. This is the same process that occurs when deploying a webpage; ASP.NET compiles the web application’s code. When this occurs on a production server, it has to do so without the .csproj file (which isn’t usually deployed, if you’ve taken your time to do a deployment cleanly). This process has merely the file system available to identify what to compile. So, back in the world of developing the webpage in visual studio on my developer box, I run into the situation because the same process is occuring there. This is true even though I have more files on my machine than will actually get deployed. I can’t help but think that this error could be attributed back to the real culprit file (Fish.cshtml, rather than the temporary files) with some work, but at least the error had enough information in it to narrow it down. The Conclusion I had previously been accustomed to the idea that for c# projects, the .csproj file always “defines” the build behavior. This investigation has taught me that I’ll need to shift my thinking a bit to remember that the file system has the final say when it comes to web applications, even on the developer’s machine!

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• Strings in .NET are Enumerable

  - by Scott Dorman

  It seems like there is always some confusion concerning strings in .NET. This is both from developers who are new to the Framework and those that have been working with it for quite some time. Strings in the .NET Framework are represented by the System.String class, which encapsulates the data manipulation, sorting, and searching methods you most commonly perform on string data. In the .NET Framework, you can use System.String (which is the actual type name or the language alias (for C#, string). They are equivalent so use whichever naming convention you prefer but be consistent. Common usage (and my preference) is to use the language alias (string) when referring to the data type and String (the actual type name) when accessing the static members of the class. Many mainstream programming languages (like C and C++) treat strings as a null terminated array of characters. The .NET Framework, however, treats strings as an immutable sequence of Unicode characters which cannot be modified after it has been created. Because strings are immutable, all operations which modify the string contents are actually creating new string instances and returning those. They never modify the original string data. There is one important word in the preceding paragraph which many people tend to miss: sequence. In .NET, strings are treated as a sequence…in fact, they are treated as an enumerable sequence. This can be verified if you look at the class declaration for System.String, as seen below: // Summary:// Represents text as a series of Unicode characters.public sealed class String : IEnumerable, IComparable, IComparable<string>, IEquatable<string> The first interface that String implements is IEnumerable, which has the following definition: // Summary:// Exposes the enumerator, which supports a simple iteration over a non-generic// collection.public interface IEnumerable{ // Summary: // Returns an enumerator that iterates through a collection. // // Returns: // An System.Collections.IEnumerator object that can be used to iterate through // the collection. IEnumerator GetEnumerator();} As a side note, System.Array also implements IEnumerable. Why is that important to know? Simply put, it means that any operation you can perform on an array can also be performed on a string. This allows you to write code such as the following: string s = "The quick brown fox";foreach (var c in s){ System.Diagnostics.Debug.WriteLine(c);}for (int i = 0; i < s.Length; i++){ System.Diagnostics.Debug.WriteLine(s[i]);} If you executed those lines of code in a running application, you would see the following output in the Visual Studio Output window: In the case of a string, these enumerable or array operations return a char (System.Char) rather than a string. That might lead you to believe that you can get around the string immutability restriction by simply treating strings as an array and assigning a new character to a specific index location inside the string, like this: string s = "The quick brown fox";s[2] = 'a';   However, if you were to write such code, the compiler will promptly tell you that you can’t do it: This preserves the notion that strings are immutable and cannot be changed once they are created. (Incidentally, there is no built in way to replace a single character like this. It can be done but it would require converting the string to a character array, changing the appropriate indexed location, and then creating a new string.)

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