ASP.NET Tutorial/Custom Controls/Basics

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Action from user-defined control

File: Control.ascx
<%@ Control Language="C#" AutoEventWireup="true" CodeFile="Control.ascx.cs" Inherits="LinkMenu" %>
<div>
  Products:
  <asp:HyperLink id="lnkBooks" runat="server"
    NavigateUrl="MenuHost.aspx?product=Books">Books
  </asp:HyperLink><br />
  <asp:HyperLink id="lnkToys" runat="server"
    NavigateUrl="MenuHost.aspx?product=Toys">Toys
  </asp:HyperLink><br />
  <asp:HyperLink id="lnkSports" runat="server"
    NavigateUrl="MenuHost.aspx?product=Sports">Sports
  </asp:HyperLink><br />
  <asp:HyperLink id="lnkFurniture" runat="server"
    NavigateUrl="MenuHost.aspx?product=Furniture">Furniture
  </asp:HyperLink>
</div>
File: Control.ascx.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class LinkMenu : System.Web.UI.UserControl
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }
}

File: MenuHost.aspx
<%@ Page Language="C#" AutoEventWireup="true"
    CodeFile="MenuHost.aspx.cs" Inherits="MenuHost"%>
<%@ Register TagPrefix="nfex" TagName="LinkMenu" Src="Control.ascx" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Menu Host</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <table >
            <tr>
                <td style="width: 100px">
                    <nfex:LinkMenu id="Menu1" runat="server" />
                </td>
                <td>
                    &nbsp;&nbsp;<asp:Label id="lblSelection" runat="server" />
                </td>
            </tr>
        </table>
    </div>
    </form>
</body>
</html>

File: MenuHost.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class MenuHost : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (Request.Params["product"] != null)
        {
            lblSelection.Text = "You chose: ";
            lblSelection.Text += Request.Params["product"];
        }
    }
}


Adding controls to the Web user control

<%@ Control Language="VB" ClassName="WebUserControl2" %>
   
<script runat="server">
   
</script>
   
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:Button ID="Button1" runat="server" Text="Button" />


ASP controls in user control

<%@ Page Language="C#" AutoEventWireup="true" %>
<%@ Register Src="Control.ascx" TagName="VaryByControl" TagPrefix="uc1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <uc1:VaryByControl ID="VaryByControl1" runat="server" />
    
    </div>
    </form>
</body>
</html>
File: Control.ascx
<%@ Control Language="C#" 
            AutoEventWireup="true" 
            CodeFile="Control.ascx.cs" 
            Inherits="VaryByControl" %>
<%@ OutputCache Duration="30" VaryByControl="lstMode"  %>
<asp:DropDownList id="lstMode" runat="server" Width="187px">
  <asp:ListItem>Large</asp:ListItem>
  <asp:ListItem>Small</asp:ListItem>
  <asp:ListItem>Medium</asp:ListItem>
</asp:DropDownList>&nbsp;<br />

Control generated at:<br /> 
<asp:label id="TimeMsg" runat="server" />

File: Control.ascx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class VaryByControl : System.Web.UI.UserControl
{
    protected void Page_Load(object sender, EventArgs e)
    {
    switch (lstMode.SelectedIndex)
    {
      case 0:
        TimeMsg.Font.Size = FontUnit.Large;
        break;
      case 1:
        TimeMsg.Font.Size = FontUnit.Small;
        break;
      case 2:
        TimeMsg.Font.Size = FontUnit.Medium;
        break;
    }
    TimeMsg.Text = DateTime.Now.ToString("F");
    }
}


A Web user control file template

<%@ Control Language="VB" ClassName="WebUserControl1" %>
    
<script runat="server">
    
</script>


Building a simple User control that randomly displays one image

Both the UserControl class and the Page class derive from the base TemplateControl class. 
Custom control is stored in the file with .ascx extension. 
You cannot request this file directly from a web browser. 

Before using a web User control, you must register it. 
<%@ Register %> directive contains the three attributes:
TagPrefix:    namespace. You can use any string that you want.
TagName:      name that you want to associate with the User control. 
              
Src:          virtual path to the User control (the path to the .ascx file).

File: Control.ascx
<%@ Control Language="C#" ClassName="RandomImage" %>
<%@ Import Namespace="System.IO" %>
<script runat="server">
    void Page_Load()
    {
        string imageToDisplay = GetRandomImage();
        imgRandom.ImageUrl = Path.rubine("~/Images", imageToDisplay);
        lblRandom.Text = imageToDisplay;
    }
    private string GetRandomImage()
    {
        Random rnd = new Random();
        string[] images = Directory.GetFiles(MapPath("~/Images"), "*.jpg");
        string imageToDisplay = images[rnd.Next(images.Length)];
        return Path.GetFileName(imageToDisplay);
    }
</script>
<asp:Image
    id="imgRandom"
    Width="300px"
    Runat="server" />
<br />
<asp:Label
    id="lblRandom"
    Runat="server" />

File: ShowRandomImage.aspx
<%@ Page Language="C#" %>
<%@ Register TagPrefix="user" TagName="RandomImage" Src="~/Control.ascx" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show RandomImage</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <user:RandomImage
        ID="RandomImage1"
        Runat="server" />
    </div>
    </form>
</body>
</html>


Building Fully Rendered Controls

File: FullyRenderedControl.cs
namespace myControls
{
    public class FullyRenderedControl : Control
    {
        private string _Text;
        public string Text
        {
            get { return _Text; }
            set { _Text = value; }
        }
        protected override void Render(HtmlTextWriter writer)
        {
            writer.Write(_Text);
        }
    }
}
File: Default.aspx
<%@ Page Language="C#" %>
<%@ Register TagPrefix="custom" Namespace="myControls" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show Fully Rendered Control</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <custom:FullyRenderedControl
        ID="FullyRenderedControl1"
        Text="Hello World!"
        runat="Server" />
    </div>
    </form>
</body>
</html>


Calculator component based on page component (VB.net)

File: index.aspx
<%@ Page language="VB" %>
<%@ Register TagPrefix="nfexASP" TagName="Calculator" src="Control.ascx" %>
<html><body>
   <form runat="server">
      <nfexASP:Calculator id="Calc1" runat="server"/>
   </form>
</body></html>
File: Control.ascx
<script language="VB" runat="server">
   private answer as double
   
   Sub btOperator_Click(Sender as Object, e as EventArgs)
      if (hiddenvalue.value <> "" and hiddenvalue.value <> "0")
         tbNumber.Text = Operate(Sender.Text, hiddenvalue.value, tbNumber.Text)
         hiddenvalue.value = ""
         hiddenoperator.value = ""
      else
         hiddenvalue.value = tbNumber.Text
         hiddenoperator.value = Sender.Text
         tbNumber.Text = "0"
      end if
   End Sub
   
   Sub btSpecOperator_Click(Sender as Object, e as EventArgs)
      tbNumber.Text = Operate(Sender.Text, hiddenvalue.value, tbNumber.Text)
      hiddenvalue.value = ""
      hiddenoperator.value = ""
   End Sub
   
   Sub btNumber_Click(Sender as Object, e as EventArgs)
      response.write(answer.ToString)
      if tbNumber.Text <> "0" then
         tbNumber.Text = tbNumber.Text & Sender.Text
      else
         tbNumber.Text = Sender.Text
         answer = nothing
      end if
   end sub
   
   Sub btClear_Click(Sender as Object, e as EventArgs)
      tbNumber.Text = "0"
      hiddenoperator.value = ""
      hiddenvalue.value = ""
   end sub
   
   Sub btBS_Click(Sender as Object, e as EventArgs)
      if tbNumber.Text <> "0" then
         tbNumber.Text = Left(tbNumber.Text, len(tbNumber.Text)-1) 
      end if
   end sub
   
   Sub btMemory_Click(Sender as Object, e as EventArgs)
      select case Sender.text
         case "MC"
            Session("memory") = ""
            Indicator.Text = ""
         case "MS"
            Session("memory") = tbNumber.Text
            Indicator.Text = "M"
         case "MR"
            tbNumber.Text = Session("Memory")
         case "M+"
            
      end select
   end sub
   
   Sub btEqual_Click(Sender as object, e as EventArgs)
      if hiddenvalue.value <> "" then
         if hiddenoperator.value <> "" then
            tbNumber.Text = Operate(hiddenoperator.value, hiddenvalue.value, tbNumber.Text)
            hiddenvalue.value = ""
            hiddenoperator.value = ""
            answer = tbNumber.Text
         else
            "do nothing
         end if
      else
         "do nothing
      end if
   end sub
   
   private function Operate(op as string, number1 as string, number2 as string ) as double
      select case op
         case "+"
            Operate = CDbl(number1) + CDbl(number2)
         case "-"
            Operate = CDbl(number1) - CDbl(number2)
         case "*"
            Operate = CDbl(number1) * CDbl(number2)
         case "/"
            Operate = CDbl(number1) / CDbl(number2)
         case "sqrt"
            Operate = CDbl(Math.sqrt(number2))
         case "1/x"
            Operate = CDbl(1 / cdbl(number2))
         case "+/-"
            Operate = CDbl(-cdbl(number2))
      end select
   end function
</script>   
<asp:Panel id="Frame" runat="server">
   <table width="250">
   <tr>
      <td width="100%" colspan="7">
         <asp:textbox id="tbNumber" runat=server
            text="0"
            enabled="false"
            width="100%" />
      </td>
   </tr>
   <tr>
      <td align="right" width="100%" colspan="7">
         <asp:Label id="Indicator" text="" runat="server" />
         <asp:button id="btBS" Text="Backspace" 
            OnClick="btBS_Click" runat=server width="75"/>
         <asp:button id="btClear" Text="C" 
            OnClick="btClear_Click" runat=server width="35"/>
      </td>
   </tr>  
   <tr>
      <td width="32" valign="top">
         <asp:button id="btMC" Text="MC" 
            OnClick="btMemory_Click" runat=server 
            width="35"/>
      </td>
      <td width="58"></td>
      <td width="32">
         <asp:button id="bt7" Text="7" 
            OnClick="btNumber_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="bt8" Text="8" 
            OnClick="btNumber_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="bt9" Text="9" 
            OnClick="btNumber_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="btDivide" Text="/" 
            OnClick="btOperator_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="btSqrt" Text="sqrt" 
            OnClick="btSpecOperator_Click" runat=server 
            width="35"/>
      </td>
   </tr>
   <tr>
      <td width="32" valign="top">
         <asp:button id="btMR" Text="MR" 
            OnClick="btMemory_Click" runat=server 
            width="35"/>
      </td>
      <td width="8"></td>
      <td width="32">
         <asp:button id="bt4" Text="4" 
            OnClick="btNumber_Click" 
            runat=server width="35"/>   
      </td>
      <td width="32">
         <asp:button id="bt5" Text="5" 
            OnClick="btNumber_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="bt6" Text="6" 
            OnClick="btNumber_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="btMultiply" Text="*" 
            OnClick="btOperator_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="btPercent" Text="%" 
            OnClick="btOperator_Click" runat=server 
            width="35"/>
      </td>
   </tr>  
   <tr>
      <td width="32" valign="top">
         <asp:button id="btMS" Text="MS" 
            OnClick="btMemory_Click" runat=server 
            width="35"/>
      </td>
      <td width="8"></td>
      <td width="32">
         <asp:button id="bt1" Text="1" 
            OnClick="btNumber_Click" runat=server 
            width="35"/>   
      </td>
      <td width="32">
         <asp:button id="bt2" Text="2" 
            OnClick="btNumber_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="bt3" Text="3" 
            OnClick="btNumber_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="btSubtract" Text="-" 
            OnClick="btOperator_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="btOneOver" Text="1/x" 
            OnClick="btSpecOperator_Click" runat=server 
            width="35"/>
      </td>
   </tr> 
   <tr>
      <td width="32" valign="top">
         <asp:button id="btMP" Text="M+" 
            OnClick="btMemory_Click" runat=server 
            width="35"/>
      </td>
      <td width="8"></td>
      <td width="32">
         <asp:button id="bt0" Text="0" 
            OnClick="btNumber_Click" runat=server 
            width="35"/>   
      </td>
      <td width="32">
         <asp:button id="btNegate" Text="+/-" 
            OnClick="btSpecOperator_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="btDot" Text="." 
            OnClick="btNumber_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="btAdd" Text="+" 
            OnClick="btOperator_Click" runat=server 
            width="35"/>
      </td>
      <td width="32">
         <asp:button id="btEqual" Text="=" 
            OnClick="btEqual_Click" runat=server 
            width="35"/>
      </td>
   </tr> 
   </table>
</asp:Panel>
<input type="hidden" id="hiddenvalue" value="" 
   runat="server" >
<input type="hidden" id="hiddenoperator" value="" 
   runat="server" >


Component level variable

<%@Import Namespace="System.Drawing" %>
<%@Register TagPrefix="CodingStrategies" TagName="Color" Src="Control.ascx" %>
<script language="C#" runat="server">
protected void SetColor(object o, EventArgs e) {
    Color color = Color.FromName(theTextbox.Text);
    colorControl.Color = color;
}
</script>
<form runat="server">
Name your favorite color
<asp:textbox runat="server" id="theTextbox" OnTextChanged="SetColor" Value="Black"/><br />
Your favorite color is: <CodingStrategies:Color runat="server" id="colorControl" /><br />
<asp:button type="submit" runat="server" Text="Go" />
</form>
File: Control.ascx
<%@Import namespace="System.Drawing" %>
<script runat="server" language="C#">
protected Color favoriteColor = Color.Black;
protected void Page_Load(Object o, EventArgs e) {
    theLabel.Text = favoriteColor.Name;   
}
public Color Color {
    set {
        favoriteColor = value;
        theLabel.Text = favoriteColor.Name;
        theLabel.ForeColor = favoriteColor;
    }
}
</script>
<h2><asp:label id="theLabel" runat="server"/></h2>


Creating control events in a user control (C#)

<%@ Control Language="C#" ClassName="WebUserControl1" %>
<script runat="server">
    protected void Page_Load(object sender, EventArgs e)
    {
        this.Label1.Text = "The quick brown fox jumped over the lazy dog";
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        this.Label1.Text = "The quick brown fox clicked the button on the page";
    }
</script>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />


Creating control events in a user control (VB)

<%@ Control Language="VB" ClassName="WebUserControl1" %>
<script runat="server">
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
        Me.Label1.Text = "The quick brown fox jumped over the lazy dog"
    End Sub
        
    Protected Sub Button1_Click(ByVal sender As Object, _
       ByVal e As System.EventArgs)
        Me.Label1.Text = "The quick brown fox clicked the button on the page"
    End Sub
</script>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />


Day minder page component

<%@ Page Language="VB" debug="true" %>
<%@ Register TagPrefix="nfexASP" TagName="Planner" src="Control.ascx" %>
<html><body>
   <form runat="server">
      <nfexASP:Planner id="Planner" runat="server" /> 
   </form>
</body></html>
File: Control.ascx
<script language="VB" runat="server">
   Public sub Page_Load(Sender as Object, e as EventArgs)
      if not Page.IsPostBack then
         Session.Clear
         Calendar1.SelectedDate = DateTime.Now
         DayLabel.Text = Calendar1.SelectedDate. _
            ToString("dddd, MMMM dd yyyy")
      end if
   End Sub
   
   Public sub SelectionChanged(Sender as Object, e as EventArgs)
      DayLabel.Text = Calendar1.SelectedDate. _
         ToString("dddd, MMMM dd yyyy")
      
      if not (Session(Calendar1.SelectedDate.ToString) is nothing)
         dim l as Label = new label
         l.Text = Session(Calendar1.SelectedDate.ToString)
         DayPanel.Controls.Add(l)
      end if
   End Sub
   
   Public sub NoteChanged(Sender as Object, e as EventArgs)
      if Sender.text <> "" then
         dim l as Label = New Label
         l.text = "<li>" & Sender.Text & "</li>"
      
         DayPanel.Controls.Add(l)
         Session(Calendar1.SelectedDate.ToString) = l.text
         NoteBox.Text = ""
      end if
   End Sub
</script>
<table width="100%">
<tr>
   <td width="50%" valign="top">
      <font face="arial">
         <asp:Label id="DayLabel" 
            runat="server" 
            Height="25px" 
            Width="100%"
            BackColor="blue" 
            ForeColor="white"
            Font-Bold="true"/>
         <br>
         <asp:Panel id="DayPanel" 
            runat="server"
            backcolor="#ffffff" 
            Height="225px" >
            
            <asp:Textbox id="NoteBox" 
               runat="server"
               OnTextChanged="NoteChanged"
               TextMode="Multiline"
               Rows=5 
               Width="100%" 
               AutoPostBack="true" />
         </asp:Panel>
      </font>
   </td>
   <td width="50%" rowspan="2" valign="top">
      <asp:Calendar id="Calendar1" 
         runat="server"
         OnSelectionChanged="SelectionChanged"
         Cellpadding="5" 
         Cellspacing="5"
         DayHeaderStyle-Font-Bold="True"
         DayNameFormat="Short"
         Font-Name="Arial" 
         Font-Size="12px"
         height="250px"
         NextPrevFormat="ShortMonth"
         NextPrevStyle-ForeColor="white"
         SelectedDayStyle-BackColor="#ffcc66"
         SelectedDayStyle-Font-Bold="True"
         SelectionMode="DayWeekMonth"
         SelectorStyle-BackColor="#99ccff"
         SelectorStyle-ForeColor="navy"
         SelectorStyle-Font-Size="9px"
         ShowTitle="true"
         TitleStyle-BackColor="#ddaa66"
         TitleStyle-ForeColor="white"
         TitleStyle-Font-Bold="True"
         TodayDayStyle-Font-Bold="True" />
   </td>
</tr>
</table>


Exposing user control properties (C#)

<%@ Control Language="C#" ClassName="WebUserControl" %>
<script runat="server">
    private string _text;
    
    public string Text
    {
        get {
            return _text;
        }
        set {
            _text = value;
        }
    }
    
    protected void Page_Load(object sender, EventArgs e)
    {
        this.Label1.Text = this.Text;
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        this.Label1.Text = "The quick brown fox clicked the button on the page";
    }
</script>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />


Exposing user control properties (VB)

<%@ Control Language="VB" ClassName="WebUserControl" %>
<script runat="server">
    Private _text As String
    
    Public Property Text() As String
        Get
            Return _text
        End Get
        Set(ByVal value As String)
            _text = value
        End Set
    End Property
    
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
        Me.Label1.Text = Me.Text
    End Sub
        
    Protected Sub Button1_Click(ByVal sender As Object, _
      ByVal e As System.EventArgs)
        Me.Label1.Text = "The quick brown fox clicked the button on the page"
    End Sub
</script>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />


Pass parameter from user-defined controls to host page

File: Control.ascx
<%@ Control Language="C#" AutoEventWireup="true" CodeFile="Control.ascx.cs" Inherits="Control" %>
<div>
    Products:
    <asp:LinkButton ID="lnkBooks" runat="server" CommandArgument="MenuHost.aspx?product=Books" OnCommand="lnk_Command" >Books
  </asp:LinkButton><br />
    <asp:LinkButton ID="lnkToys" runat="server" CommandArgument="MenuHost.aspx?product=Toys" OnCommand="lnk_Command">Toys
  </asp:LinkButton><br />
    <asp:LinkButton ID="lnkSports" runat="server" CommandArgument="MenuHost.aspx?product=Sports" OnCommand="lnk_Command">Sports
  </asp:LinkButton><br />
    <asp:LinkButton ID="lnkFurniture" runat="server" CommandArgument="MenuHost.aspx?product=Furniture" OnCommand="lnk_Command">Furniture
  </asp:LinkButton>
</div>
File: Control.ascx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class LinkMenu : System.Web.UI.UserControl
{
    public event LinkClickedEventHandler LinkClicked;
    protected void lnk_Command(object sender, CommandEventArgs e)
    {
        if (LinkClicked != null)
        {
            LinkClickedEventArgs args = new LinkClickedEventArgs((string)e.rumandArgument);
            LinkClicked(this, args);
            if (!args.Cancel)
            {
                Response.Redirect(args.Url);
            }
        }
    }
}
File: MenuHost.aspx

<%@ Page Language="C#" AutoEventWireup="true"
    CodeFile="MenuHost.aspx.cs" Inherits="MenuHost"%>
<%@ Register TagPrefix="nfex" TagName="LinkMenu" Src="Control.ascx" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Menu Host</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <table>
            <tr>
                <td style="width: 100px">
                    <nfex:LinkMenu id="Menu1" runat="server" OnLinkClicked="LinkClicked" />
                </td>
                <td>
                    &nbsp;&nbsp;<asp:Label id="lblSelection" runat="server" EnableViewState="false"/><br />
                    &nbsp;&nbsp;<asp:Label id="lblClick" runat="server" EnableViewState="false"/>
                </td>
            </tr>
        </table>
        <br />
        &nbsp;
    </div>
    </form>
</body>
</html>

File: MenuHost.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public class LinkClickedEventArgs : EventArgs
{
    private string url;
    public string Url
    {
        get { return url; }
        set { url = value; }
    }
    private bool cancel = false;
    public bool Cancel
    {
        get { return cancel; }
        set { cancel = value; }
    }
    public LinkClickedEventArgs(string url)
    {
        Url = url;
    }
}
public delegate void LinkClickedEventHandler(object sender,  LinkClickedEventArgs e);

public partial class MenuHost : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            if (Request.Params["product"] != null)
            {
                lblSelection.Text = "You chose: ";
                lblSelection.Text += Request.Params["product"];
            }
        }
    }
    protected void LinkClicked(object sender, LinkClickedEventArgs e)
    {
        if (e.Url == "MenuHost.aspx?product=Furniture")
        {
            lblClick.Text = "This link is not allowed.";
            e.Cancel = true;
        }
    }
}


Populating user control properties from the host Web page (C#)

<%@ Page Language="C#" %>
<%@ Register Src="Control.ascx" TagName="WebUserControl" TagPrefix="uc1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
    protected void Page_Load(object sender, EventArgs e)
    {
        this.WebUserControl1.Text = "The quick brown fox jumped over the lazy dog";
    }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <uc1:WebUserControl id="WebUserControl1" runat="server">
        </uc1:WebUserControl></div>
    </form>
</body>
</html>
File: Control.ascx
<%@ Control Language="C#" ClassName="WebUserControl" %>
<script runat="server">
    private string _text;
    
    public string Text
    {
        get {
            return _text;
        }
        set {
            _text = value;
        }
    }
    
    protected void Page_Load(object sender, EventArgs e)
    {
        this.Label1.Text = this.Text;
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        this.Label1.Text = "The quick brown fox clicked the button on the page";
    }
</script>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />


Populating user control properties from the host Web page (VB)

<%@ Page Language="VB" %>
<%@ Register Src="Control.ascx" TagName="WebUserControl"
    TagPrefix="uc1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
    Me.WebUserControl1.Text = "The quick brown fox jumped over the lazy dog"
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <uc1:WebUserControl ID="WebUserControl1" runat="server" />
    </div>
    </form>
</body>
</html>
File: Control.ascx
<%@ Control Language="VB" ClassName="WebUserControl" %>
<script runat="server">
    Private _text As String
    
    Public Property Text() As String
        Get
            Return _text
        End Get
        Set(ByVal value As String)
            _text = value
        End Set
    End Property
    
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
        Me.Label1.Text = Me.Text
    End Sub
        
    Protected Sub Button1_Click(ByVal sender As Object, _
      ByVal e As System.EventArgs)
        Me.Label1.Text = "The quick brown fox clicked the button on the page"
    End Sub
</script>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />


Registering User Controls in the Web Configuration File

File: Control.ascx
<%@ Control Language="C#" ClassName="RandomImage" %>
<%@ Import Namespace="System.IO" %>
<script runat="server">
    void Page_Load()
    {
        string imageToDisplay = GetRandomImage();
        imgRandom.ImageUrl = Path.rubine("~/Images", imageToDisplay);
        lblRandom.Text = imageToDisplay;
    }
    private string GetRandomImage()
    {
        Random rnd = new Random();
        string[] images = Directory.GetFiles(MapPath("~/Images"), "*.jpg");
        string imageToDisplay = images[rnd.Next(images.Length)];
        return Path.GetFileName(imageToDisplay);
    }
</script>
<asp:Image
    id="imgRandom"
    Width="300px"
    Runat="server" />
<br />
<asp:Label
    id="lblRandom"
    Runat="server" />
    
File: Web.Config
<configuration>
<system.web>
  <pages>
    <controls>
      <add
        tagPrefix="user"
        tagName="RandomImage"
        src="~/UserControls/Control.ascx"/>
    </controls>
  </pages>
</system.web>
</configuration>

After you register a User control in the web configuration file, you can declare the User control in any page. 
File: Default.aspx
<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show Application Register</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <user:RandomImage
        ID="RandomImage1"
        Runat="Server" />
    </div>
    </form>
</body>
</html>


Use custom control in Assembly

<%@ Page Language="VB" %>
<%@ Register TagPrefix="nfexASP" Namespace="MyCustomControls" Assembly="CustomControls"%>
<html><body>
   <form runat=server>
      The custom control produces the following output:
   
      <nfexASP:CustomControl1 id="MyControl" runat=server/>
   </form>
</body></html>
//////C#
using System;
using System.Web;
using System.Web.UI;
    
namespace MyCustomControls {
   public class CustomControl1 : Control {
      protected override void Render(HtmlTextWriter Output) {
         Output.Write("This is my custom control! ");
      }
   }
}
//////VB
Imports System
Imports System.Web
Imports System.Web.UI
Namespace MyCustomControls
   Public Class CustomControl1 : Inherits Control
      Protected Overrides Sub Render(Output as HtmlTextWriter)
         Output.Write("This is my custom control! ")
      End Sub
   End Class
End Namespace


User control with property

<%@ Page Language="C#" %>
<%@ Register TagPrefix="apress" TagName="TimeDisplay" Src="Control.ascx" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<script runat="server">
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <apress:TimeDisplay id="TimeDisplay1" 
  Format="dddd, dd MMMM yyyy HH:mm:ss tt (GMT z)" runat="server" />
<hr />
<apress:TimeDisplay id="TimeDisplay2" runat="server" />
    </div>
    </form>
</body>
</html>
File: Control.ascx
<%@ Control Language="C#" 
            AutoEventWireup="true" 
            CodeFile="Control.ascx.cs" 
            Inherits="TimeDisplay" %>
<br />
<asp:LinkButton runat="server" ID="lnkTime" OnClick="lnkTime_Click"/>
File: Control.ascx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class TimeDisplay : System.Web.UI.UserControl
{
  protected void Page_Load(object sender, EventArgs e)
  {
    RefreshTime();
  }
  protected void lnkTime_Click(object sender, EventArgs e)
  {
    RefreshTime();
  }
  public void RefreshTime()
  {
    if (format == "")
    {
      lnkTime.Text = DateTime.Now.ToLongTimeString();
    }
    else
    {
      lnkTime.Text = DateTime.Now.ToString(format);
    }
  }
  private string format;
  public string Format
  {
    get { return format; }
    set { format = value; }
  }
}
Источник — «http://nfex.ru/index.php?title=ASP.NET_Tutorial/Custom_Controls/Basics&oldid=3334»