Beginning Silverlight 2.0 Development using Visual Studio 2008 - Basic Data Binding in Silverlight 2.0: explanation
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Basically, Silverlight applications execute and run on the client side (browser). No code is executed at the web server level. If Silverlight applications were executed at the server level, we'd simply have another ASP.NET!
As Silverlight applications execute at the browser level, we are left with no way to communicate with databases directly. So, we will not be able to bind to databases directly. The best options for getting the data from databases are through either web services or WCF (Windows Communication Foundation) services.
Web Services or WCF components serialize objects (data) and throw them to browser. Once the browser receives them, Silverlight can automatically pick them up and bind the same to Silverlight controls. That is the reason we will be working and binding objects to controls for all kinds of Silverlight applications.
In the previous section, we defined a simple class as follows:
Public Class Emp
Private _Empno As String
Public Property Empno() As String
Get
Return _Empno
End Get
Set(ByVal value As String)
_Empno = value
End Set
End Property
Private _Ename As String
Public Property Ename() As String
Get
Return _Ename
End Get
Set(ByVal value As String)
_Ename = value
End Set
End Property
End Class
The above class simply encapsulates employee number and employee name information. Once the class is defined, we need to instantiate and bind it to Silverlight controls. Currently, to make this article simple, I instantiated the above class with the following statement (along with some sample data):
Dim objEmp As New Emp With {.Empno = "1001", .Ename = "Jag"}
The binding in between the instantiated object and text boxes is made possible using the “Datacontext” property of the controls themselves:
Me.txtEmpno.DataContext = objEmp
Me.txtEname.DataContext = objEmp
We are assigning the same object to both text boxes. But the data gets displayed differently in each of the text boxes. The following declarations made it happen:
<TextBox Height="20" Width="142" Canvas.Left="170" Canvas.Top="52.269" Text="{Binding Empno}" TextWrapping="Wrap" x:Name="txtEmpno"/>
<TextBox Height="20" x:Name="txtEname" Width="142" Text="{Binding Ename}" TextWrapping="Wrap" Canvas.Left="170" Canvas.Top="91.269"/>
The most important attribute on which to concentrate is the “Text” property of TextBox. You can observe that the binding specification is provided with the keyword “Binding” together with the property (of Emp object) to which it needs to bind. It is important to make sure that this information is embedded in braces.
In my upcoming articles, we will see more and more examples of Silverlight 2.0 development. I hope you enjoyed the article and any suggestions, bugs, errors, enhancements etc. are highly appreciated at http://jagchat.spaces.live.com
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