User control based on System.Web.UI.WebControls.Label (VB)
<%@ Page language="VB" %>
<%@ Register TagPrefix="Control" Namespace="Control" Assembly="Control" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<html>
<head>
<title>Extending Existing Web Controls</title>
</head>
<body>
<form id="Form1" method="post" runat="server">
<Control:RainbowLabel text="This is a rainbow colored test string" runat="server" /><br/>
<Control:RainbowLabel EnableRainbowMode="false" text="This is a test string" runat="server" />
</form>
</body>
</html>
File: Control.vb
Imports System
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.ComponentModel
Namespace Control
Public Class RainbowLabel
Inherits System.Web.UI.WebControls.Label
Public Property EnableRainbowMode() As Boolean
Get
If ViewState("EnableRainbowMode") Is Nothing Then
Return True
Else
Return Boolean.Parse(CStr(ViewState("EnableRainbowMode")))
End If
End Get
Set(ByVal Value As Boolean)
ViewState("EnableRainbowMode") = Value
End Set
End Property
Protected Overrides Sub Render(ByVal output As HtmlTextWriter)
If EnableRainbowMode Then
output.Write(ColorizeString([Text]))
Else
output.Write([Text])
End If
End Sub 'Render
Private Function ColorizeString(ByVal input As String) As String
Dim output As New System.Text.StringBuilder(input.Length)
Dim rand As Random = New Random(DateTime.Now.Millisecond)
Dim i As Integer
For i = 0 To input.Length - 1
Dim red As Integer = rand.Next(0, 255)
Dim green As Integer = rand.Next(0, 255)
Dim blue As Integer = rand.Next(0, 255)
output.Append("<font color=""#")
output.Append(Convert.ToString(red, 16))
output.Append(Convert.ToString(green, 16))
output.Append(Convert.ToString(blue, 16))
output.Append(""">")
output.Append(input.Substring(i, 1))
output.Append("</font>")
Next i
Return output.ToString()
End Function 'ColorizeString
End Class 'RainbowLabel
End Namespace