mytextbox.vb

This is a book about vb.you could learn this from this book

Imports System
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Collections.Specialized

Namespace WroxControls

   Public Class MyTextBoxState
      Inherits WebControl
      Implements IPostBackDataHandler, INamingContainer
      
      Public Sub New()
         MyBase.New("input")
         Context.Trace.Write("MyTextBox", "Created")
      End Sub 'New
      
	  Private Shared _textChanged As New Object()

	  Public Event TextChanged As EventHandler
	  
    
      Private _value As String
            
      Public Property Text As String
         Get
         	If ViewState("value") = "" Then
         		Return ""
         	End If
         		
            Return ViewState("value")
         End Get
         Set
         	ViewState("value") = value
         End Set
      End Property
       
      Protected Overrides Sub AddAttributesToRender(writer As HtmlTextWriter)

         MyBase.AddAttributesToRender(writer)
         writer.AddAttribute(HtmlTextWriterAttribute.Name, UniqueID)
         
         writer.AddAttribute(HtmlTextWriterAttribute.Type, "input")
         If Not (_value Is Nothing) Then
            writer.AddAttribute("value", _value)
         End If

      End Sub
       
      Function LoadPostData(postDataKey As String, postCollection As NameValueCollection) As Boolean _
		Implements IPostBackDataHandler.LoadPostData
		
		Dim re As Boolean = False
		
		Context.Trace.Write("MyTextBox", "Previous value:" & Text)
		
		If Text <> postCollection(postDataKey) Then
			re = True
		End If

         Text = postCollection(postDataKey)
         
         Return re
      End Function 
      
      
      Sub RaisePostDataChangedEvent() _
		  Implements IPostBackDataHandler.RaisePostDataChangedEvent
         
			dim eventhandler as EventHandler

			eventhandler = CType( Events(_textChanged), EventHandler )

            RaiseEvent TextChanged(Me, EventArgs.Empty)
      End Sub
   End Class 

End Namespace