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- Introduction
- Declaring a Simple Custom Control
- Extending Existing Web Controls
- Creating ViewState-Enabled Control Properties
- Creating a Composite Control
- Creating a Data-bound Control
- Creating a Templated Control
- Dynamically Adding Controls to a Web Form
- Using the Treeview IE Web Control
- Using the TabControl and PageView IE Web Controls
- Using the ToolBar IE Web Control
- Data-binding a TreeView Control
- Installing a Component in the Global Assembly Cache (GAC)
This chapter is from the book
This chapter is from the book
This chapter is from the book
This chapter is from the book
3.3. Creating ViewState-Enabled Control Properties
You want your control's properties to retain their state using ViewState.
Technique
This example shows you how to create properties for your controls that retain their state using ViewState.
The ViewStateControl class:
Imports System
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.ComponentModel
Public Class ViewStateControl
Inherits System.Web.UI.WebControls.WebControl
Public Property [Text]() As String
Get
Dim _text As String = CStr(ViewState("Text"))
If _text Is Nothing Then
Return String.Empty
Else
Return _text
End If
End Get
Set(ByVal Value As String)
ViewState("Text") = Value
End Set
End Property
Protected Overrides Sub Render(ByVal writer As HtmlTextWriter)
writer.Write([Text])
End Sub
End Class
To use this control, you need to do the following:
<%@ Page language="VB" %> <%@ Register TagPrefix="AspNetCookbook" Namespace="AspNetCookbook" Assembly="AspNetCookbook" %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" > <html> <head> <title>Recipe0303</title> </head> <body> <script language="VB" runat="server"> Sub Page_Load(Sender As Object, E As EventArgs) If Not IsPostBack Then Dim RandomGenerator As Random RandomGenerator = New Random(DateTime.Now.Millisecond) ViewStateControl1.Text = RandomGenerator.Next(1,100) End If End Sub </script> <form id="Form1" method="post" runat="server"> <AspNetCookbook:ViewStateControl id="ViewStateControl1" runat="server"/> <asp:linkbutton text="PostBack test" runat="server"/> </form> </body> </html>
Comments
This control property called Text will retain its state on postbacksβas you see, it is quite easy to get properties to retain their state by using the ViewState property, and this technique is recommended for most Web Control properties.
See Also
Section 3.1, "Declaring a Simple Custom Control"