Adding custom EndPoint Behavior at client side ServiceReferences.ClientConfig

A custom Endpoint behavior which implements IEndpointBehavior can be added for many purposes. That depends upon your requirements and the nature of the application you are working on. But interesting thing is you cannot add the EndpointBehavior through config in Silverlight 4. But supports addition of custom Endpoint Behaviors through code .ie after creating the proxy you may add the behavior to the Endpoint.Behaviors collection of proxy.As you know, here proxy is a derived class of ClientBase<T> and this class has the property Endpoint.

Passing ClientBase<T> objects as method arguments
Next question comes how to make the code to add end point more generic in order to reuse the code for all the WCF service proxies.ie we need to write a method which accepts ClientBase<T>.This is little tricky at first look .But please don’t go for dynamic keyword or object where we have a typed way.Here is the small code snippet to use ClientBase<T> as method parameter type in C#.

private void CreateProxy()
{
    TestServiceReference.TestServiceClient client = new TestServiceReference.TestServiceClient();
    AddMyEndpointBahavior < TestServiceReference.ITestService>(client);
}
private void AddMyEndpointBahavior<T>(ClientBase<T> client) where T :class
{
    client.Endpoint.Behaviors.Add(new MyEndpointBehavior());
}

For VB.Net version see my general coding blog where I posted this first since it is more related to generics.

Changing Application.RootVisual at runtime

If you are a Silverlight Island programmer, this will not applicable to you because you will never face a situation which demands to change the Application.RootVisual property. Don’t confuse the word Island programmer ,it simply refers to the programmers who are creating small sized Silverlight applications mainly with some animations to fit into a small portion of HTML page which may be static or emitted by technologies such as ASP.Net or PHP.

Sometimes I feel that the Silverlight is more suited to Island programs than full window business apps. There are so many reasons.One is its rich user interface capabilities.This is more needed for glazy island apps than business apps. When we talk about great user experience there is always some cost attached to it which reduces performance. The performance is more important when we come to business apps than the user interface. In some of the tests we could see that the UI rendering takes more time than the WCF service in the whole display cycle. This happens when the data elements are huge in number but small and has complex data templates.

Ok.Coming back to changing Application.RootVisual multiple times at runtime. There may be scenarios where you need to show your authentication UI first and then load your application XAPs and the actual UI pages. In this case you need to change the RootVisual for sure.But this is not supported by the Silverlight runtime. First of all if you simply change, it will not change.You will get the below exception when you try to set null first and assign another visual after that.

Invalid value set for application's RootVisual

ie the below code will result into System.InvalidOperationException' in System.Windows.dll

'This will result in System.InvalidOperationException occurred in System.Windows.dll
Application.Current.RootVisual = Nothing
Application.Current.RootVisual = New TextBox With {.Text = "changed"}

So what is the simple solution.Keep a ContentControl as your RootVisual and set your Login UI and Application UI pages as its content.In the Application_Startup event set a ContentControl as your RootVisual then add initial UI to that. Later cast the RootVisual as ContentControl and change its Content property.

Private Sub Application_Startup(ByVal o As Object, ByVal e As StartupEventArgs) Handles Me.Startup
    'Initial UI.Here its button
    Dim btnChangeRootVisual As New Button() With {.Content = "Change RootVisual"}
    AddHandler btnChangeRootVisual.Click, AddressOf btnChangeRootVisual_Click
    
    'ContentControl as RootVisual
    Me.RootVisual = New ContentControl() With {.Content = btnChangeRootVisual}
End Sub
Private Sub btnChangeRootVisual_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
    'Get the ContentControl and assign new UI to its content property
    Dim rootContentControl As ContentControl = DirectCast(Application.Current.RootVisual, ContentControl)
    rootContentControl.Content = New TextBox With {.Text = "changed"}
End Sub

This is just a hack for real business application programmers of Silverlight.

Parser internal error: Object writer 'xClassNotDerivedFromElement'

If you are a Silverlight developer there is a chance that you may get the exception “Parser internal error: Object writer 'xClassNotDerivedFromElement'” very rarely which is difficult to track.Even you can’t put break points to track this.As a developer you will google the same.But most probably you will not get any results.

Only thing went wrong here is the namespace.But this is not at all mentioned in any of the exception details.ie The project which you are working on will not have a namespace or somebody in the project might forgot put the namespace in XAML or code files.

So make sure that there is namespace present in the project and the xaml files are correctly mapped to the corresponding code files in the x:Class attribute.

Note : We cannot have Silverlight projects without namespace.

I came to see this exception when one of my colleagues tried to write code which should  compile in both Silverlight 4 and WPF 4.

Color / SolidColorBrush object from color name in silverlight

The situation lead to this post was one of my friend's query.He just wants to set Background of something with a Color name in hand.
Basically string "Green" should be converted into Color object.
It seems like a silly thing as we have enough experience in .net.(I assume that persons wont jump into silverlight without basic skills in .net or jscript).But this becomes complicated when we are not able find out the method 'Color.FromName()'.
We were not able to find out a direct method which meets his requirement.But at last we arrived on the following.

private void Button_Click(object sender, RoutedEventArgs e) { 
string s = "<solidcolorbrush> xmlns='http://schemas.microsoft.com/client/2007'";

s+=" xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'" ;

s+=" Color='Green'/>";

SolidColorBrush brush =(SolidColorBrush) XamlReader.Load(s);

LayoutRoot.Background = brush;

}

It is nothing but creating a SolidColorBrush object from xaml where he can insert the color name in string.

Multiline TextBox in Silverlight 2.0

Its set of workarounds only.There is no support in silverlight 2.0 to have a multiline textbox.But we should accomplish as we might be in deadline :-).It leads to workarounds.
What I did ,was to set AcceptsReturn property of TextBox.Now it will accept Returns ie EnterKey and create one more line by increasing its' Height.
Now the next problem came.ScrollBars..
I tried setting ScrollViewer.VerticalScrollBarVisibility="Visible".But it gave me runtime error.(Dont know why VS2008 showed intellisense to add ScrollViewer.VerticalScrollBarVisibility="Visible").
Again workaround.Put this TextBox in a ScrollViewer.
Finally it looks like

<ScrollViewer Height="100" Width="100" HorizontalScrollBarVisibility="Visible">

<TextBox Text="Javascripting Silverlight 2.0"

AcceptsReturn="True"

/>

ScrollViewer>

Sample located here