Silverlight utility tip series: 57. Binding in Silverlight (2)-data verification

This article describes how to verify Binding data in Silverlight.

Notifyonvalidationerror: Whether to trigger the bindingvalidationerror event when an exception or error message occurs.

Validatesonexceptions: Whether to display the exception information as an error message.

Validatesondataerrors: Use the idataerrorinfo interface to Display Error information.

Bindingvalidationerror: This is a routing event. When the source object a bound to data has an error, an exception is thrown to receive and trigger this event, when the source object A does not have the bindingvalidationerror event, it receives and triggers the bindingvalidationerror event of its parent object.

First, we write a user class and throw the following exception when performing a simple verification error in the attribute:Code:

     Public   Class User
{
 Private   String M_username;

 Public   String Username
{
 Get { Return M_username ;}
 Set  
{
 If (Value. Length < 3 )
{
 Throw   New Exception ( " The user name must be less than 3 characters long  " );
}
M_username = value;
}
}

 Private   String M_userpwd;

 Public   String Userpwd
{
 Get { Return M_userpwd ;}
 Set  
{
 If (Value. Length < 6 )
{
 Throw   New Exception ( "  Password Length cannot be less than 6  " );
}
M_userpwd = value;
}
}
}

 

Then let's take a look at the XAML code to demonstrate a Data Binding interface during logon:

<Grid X: Name ="  Layoutroot  " Background = "  White  " >
<Canvas name = "  Canvasuser  " Bindingvalidationerror = "  Canvasuser_bindingvalidationerror  " 
Loaded = "  Canvasuser_loaded " >
<SDK: Label Height = "  28  " Name = "  Lbpwd  " Width = "  55  " Canvas. Left = "  16  " Canvas. Top = "  51 " 
Content = "  Password:  " />
<SDK: Label canvas. Left = "  16  " Canvas. Top = "  15  " Height = "  28  " Name = " Lbusername  " 
Width = "  55  " Content = "  User name:  " />
<Textbox X: Name = "  Tbusername  " Width = "  88  " Margin ="  10  " 
TEXT = "  {Binding Path = username, mode = twoway,  
 Notifyonvalidationerror = true, validatesonexceptions = true} "
 Canvas. Left = "  91  " Canvas. Top = "  5  " />
<Textbox X: Name = "  Tbuserpwd  " Width = "  88  " Margin = "  10  " 
TEXT = "  {Binding Path = userpwd, mode = twoway,  
 Notifyonvalidationerror = false, validatesonexceptions = true} "
 Canvas. Left = "  91  " Canvas. Top = "  45  " />
<Button Height = "  30  " Width = "  70  " Content = "  Submit  " 
Canvas. Left = "  54  " Canvas. Top = "  93  " />
</Canvas>
</GRID>

Finally, bind the user class to the original interface at the front end, and change the textbox border to red when describing the bindingvalidationerror event.

     Public   Partial   Class Mainpage: usercontrol
{
 Public Mainpage ()
{
Initializecomponent ();
}

 Private   Void Canvasuser_bindingvalidationerror ( Object Sender, validationerroreventargs E)
{

Textbox TB = E. originalsource As Textbox;
 If (E. Action = validationerroreventaction. added)
{
TB. borderbrush = New Solidcolorbrush (colors. Red );
}
 Else   If (E. Action = validationerroreventaction. removed)
{
TB. borderbrush = New Solidcolorbrush (colors. White );
}
}

 Private   Void Canvasuser_loaded ( Object Sender, routedeventargs E)
{
 This . Canvasuser. datacontext = New User ();
}
}

If the actual result is true, an error is automatically prompted when you enter a non-specific metric value. If you need the source code, click slbinding2.rar to download it.