Mutually exclusive RadioButton in INamingContainer redux

Some time back I'd posted about the bug with mutually excusive radiobuttons in repeater controls for VB.Net and hacking my way around the bug. Well, since some time I'd been thinking of posting how I actually did it for the benefit of others and today is the day! As they say, better late than never. Here's the CustomRadioButton.vb class:

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

Public Class CustomRadioButtonControl
Inherits WebControl
Implements IPostBackDataHandler

Shared Sub New()
 CustomRadioButtonControl.EventCheckedChanged = New Object
End Sub

Public Sub New()
 MyBase.New(HtmlTextWriterTag.Input)
End Sub
#Region "Properties"

Public Event CheckedChanged As EventHandler
Private Shared ReadOnly EventCheckedChanged As Object

Private ReadOnly Property UniqueGroupName() As String
 Get
     Dim grpName As String = Me.GroupName
     Dim unqId As String = Me.UniqueID
     Dim num As Integer = unqId.LastIndexOf(":"c)
     If (num >= 0) Then
         grpName = (unqId.Substring(0, (num + 1)) & grpName)
     End If
     Return grpName
 End Get
End Property


Public Overridable Property GroupName() As String
 Get
     Dim grpName As String = CType(Me.ViewState.Item("GroupName"), String)
     If (Not grpName Is Nothing) Then
         Return grpName
     End If
     Return String.Empty
 End Get
 Set(ByVal value As String)
     Me.ViewState.Item("GroupName") = value
 End Set
End Property

Public Overridable Property Checked() As Boolean
 Get
     Dim grpChecked As Object = Me.ViewState.Item("Checked")
     If (Not grpChecked Is Nothing) Then
         Return CType(grpChecked, Boolean)
     End If
     Return False
 End Get
 Set(ByVal value As Boolean)
     Me.ViewState.Item("Checked") = value
 End Set
End Property

Private ReadOnly Property SaveCheckedViewState() As Boolean
 Get
     If ((Not MyBase.Events.Item(Me.EventCheckedChanged) Is Nothing) OrElse Not Me.Enabled) Then
         Return True
     End If
     Dim baseType As Type = MyBase.GetType
     If ((Not baseType Is GetType(CheckBox)) AndAlso (Not baseType Is GetType(RadioButton))) Then
         Return True
     End If
     Return False
 End Get
End Property

Public Overridable Property AutoPostBack() As Boolean
 Get
     Dim doAutoPostBack As Object = Me.ViewState.Item("AutoPostBack")
     If (Not doAutoPostBack Is Nothing) Then
         Return CType(doAutoPostBack, Boolean)
     End If
     Return False
 End Get
 Set(ByVal value As Boolean)
     Me.ViewState.Item("AutoPostBack") = value
 End Set
End Property


Private ReadOnly Property Value() As String
 Get
     Dim val As String = Attributes("value")
     If (val Is Nothing) Then
         val = UniqueID
     End If
     Return val
 End Get
End Property

Public Overridable Property [Text]() As String
 Get
     Dim grpText As String = CType(Me.ViewState.Item("Text"), String)
     If (Not grpText Is Nothing) Then
         Return grpText
     End If
     Return String.Empty
 End Get
 Set(ByVal value As String)
     Me.ViewState.Item("Text") = value
 End Set
End Property

Public Overridable Property TextAlign() As TextAlign
 Get
     Dim align As Object = Me.ViewState.Item("TextAlign")
     If (Not align Is Nothing) Then
         Return CType(align, TextAlign)
     End If
     Return TextAlign.Right
 End Get
 Set(ByVal value As TextAlign)
     If ((value < TextAlign.Left) OrElse (value > TextAlign.Right)) Then
         Throw New ArgumentOutOfRangeException("value")
     End If
     Me.ViewState.Item("TextAlign") = value
 End Set
End Property

#End Region

Protected Overrides Sub Render(ByVal writer As HtmlTextWriter)
 If (Not Me.Page Is Nothing) Then
     Me.Page.VerifyRenderingInServerForm(Me)
 End If
 Dim doRender As Boolean = False

 If Not Me.Enabled Then
     writer.AddAttribute(HtmlTextWriterAttribute.Disabled, "disabled")
     doRender = True
 End If
 Dim tip As String = Me.ToolTip
 If (tip.Length > 0) Then
     writer.AddAttribute(HtmlTextWriterAttribute.Title, tip)
     doRender = True
 End If
 Dim _onClick As String = Nothing
 Dim _attributes As AttributeCollection = MyBase.Attributes
 Dim _value As String = _attributes.Item("value")
 If (Not _value Is Nothing) Then
     _attributes.Remove("value")
 End If
 _onClick = _attributes.Item("onclick")
 If (Not _onClick Is Nothing) Then
     _attributes.Remove("onclick")
 End If
 If (_attributes.Count <> 0) Then
     _attributes.AddAttributes(writer)
     doRender = True
 End If
 If (Not _value Is Nothing) Then
     _attributes.Item("value") = _value
 End If
 If doRender Then
     writer.RenderBeginTag(HtmlTextWriterTag.Span)
 End If
 Dim _text As String = Me.Text
 Dim _clientId As String = Me.ClientID
 If (_text.Length <> 0) Then
     If (Me.TextAlign = TextAlign.Left) Then
         Me.RenderLabel(writer, _text, _clientId)
         Me.RenderInputTag(writer, _clientId, _onClick)
     Else
         Me.RenderInputTag(writer, _clientId, _onClick)
         Me.RenderLabel(writer, _text, _clientId)
     End If
 Else
     Me.RenderInputTag(writer, _clientId, _onClick)
 End If
 If doRender Then
     writer.RenderEndTag()
 End If

End Sub

Private Sub RenderLabel(ByVal writer As HtmlTextWriter, ByVal [text] As String, ByVal clientID As String)
 writer.AddAttribute(HtmlTextWriterAttribute.For, clientID)
 writer.RenderBeginTag(HtmlTextWriterTag.Label)
 writer.Write(text)
 writer.RenderEndTag()
End Sub


#Region "Rendering"

Protected Overrides Sub OnPreRender(ByVal e As EventArgs)
 If ((Not Me.Page Is Nothing) AndAlso Me.Enabled) Then
     Me.Page.RegisterRequiresPostBack(Me)
 End If
 If Not Me.SaveCheckedViewState Then
     Me.ViewState.SetItemDirty("Checked", False)
 End If

 If (((Not Me.Page Is Nothing) AndAlso Not Me.Checked) AndAlso Me.Enabled) Then
     Me.Page.RegisterRequiresPostBack(Me)
 End If
 If (Me.GroupName.Length = 0) Then
     Me.GroupName = Me.UniqueID
 End If
End Sub

Friend Sub RenderInputTag(ByVal writer As HtmlTextWriter, ByVal clientID As String, ByVal onClick As String)
 writer.AddAttribute(HtmlTextWriterAttribute.Id, clientID)
 writer.AddAttribute(HtmlTextWriterAttribute.Type, "radio")
 writer.AddAttribute(HtmlTextWriterAttribute.Name, Me.GroupName)
 writer.AddAttribute(HtmlTextWriterAttribute.Value, Me.Value)
 If Me.Checked Then
     writer.AddAttribute(HtmlTextWriterAttribute.Checked, "checked")
 End If
 If Not Me.Enabled Then
     writer.AddAttribute(HtmlTextWriterAttribute.Disabled, "disabled")
 End If
 If Me.AutoPostBack Then
     If (Not onClick Is Nothing) Then
         onClick = (onClick & Me.Page.GetPostBackClientEvent(Me, ""))
     Else
         onClick = Me.Page.GetPostBackClientEvent(Me, "")
     End If
     writer.AddAttribute(HtmlTextWriterAttribute.Onclick, onClick)
     writer.AddAttribute("language", "javascript")
 Else
     If (Not onClick Is Nothing) Then
         writer.AddAttribute(HtmlTextWriterAttribute.Onclick, onClick)
     End If
 End If
 If (Me.AccessKey.Length > 0) Then
     writer.AddAttribute(HtmlTextWriterAttribute.Accesskey, Me.AccessKey)
 End If
 If (Me.TabIndex <> 0) Then
     writer.AddAttribute(HtmlTextWriterAttribute.Tabindex, Me.TabIndex.ToString(NumberFormatInfo.InvariantInfo))
 End If
 writer.RenderBeginTag(HtmlTextWriterTag.Input)
 writer.RenderEndTag()
End Sub

Protected Overridable Sub OnCheckedChanged(ByVal e As EventArgs)
 Dim handler As EventHandler = CType(MyBase.Events.Item(CustomRadioButtonControl.EventCheckedChanged), EventHandler)
 If (Not handler Is Nothing) Then
     handler.Invoke(Me, e)
 End If
End Sub

#End Region

#Region "IPostBackDataHandler Members"

Public Overridable Shadows Sub RaisePostDataChangedEvent() Implements IPostBackDataHandler.RaisePostDataChangedEvent
 OnCheckedChanged(EventArgs.Empty)
End Sub

Private Function LoadPostData(ByVal postDataKey As String, ByVal postCollection As NameValueCollection) As Boolean Implements IPostBackDataHandler.LoadPostData
 Dim grpName As String = postCollection.Item(Me.GroupName)
 Dim flag As Boolean = False
 If ((Not grpName Is Nothing) AndAlso grpName.Equals(Me.Value)) Then
     If Not Me.Checked Then
         Me.Checked = True
         flag = True
     End If
     Return flag
 End If
 If Me.Checked Then
     Me.Checked = False
 End If
 Return flag
End Function

#End Region
End Class

Embedding the control in your aspx page is simple, just register the tag prefix using:
<%@ Register TagPrefix="ucl" Namespace="XYZ.Website" Assembly="XYZ.Website"%>

PS: forget about how to showing the code snippet to embed it aspx page, blogger really sucks when you want to include html tags as is within your post. Basically you set the groupName property and the id property!