ASP.NET User Controls

In addition to using Web server controls in your ASP.NET Web pages, you can create your own custom, reusable controls using the same techniques you use for creating ASP.NET Web pages. These controls are called user controls.

A user control is a kind of composite control that works much like an ASP.NET Web page—you can add existing Web server controls and markup to a user control, and define properties and methods for the control. You can then embed them in ASP.NET Web pages, where they act as a unit.

SharePoint USER Controls

A user control is a control that is associated with a .ASCX extension and was originally intended for a developer to re-use within a single project.  ASP.NET developers know it is really easy to create a new user control, drag and drop some controls onto a visual designer, put some logic in the control’s code-behind, and re-use the control within a single project.  This is because the .ASCX file associated with the control enables you to create markup for your control:

<%@ Assembly Name="$SharePoint.Project.AssemblyFullName$" %>

<%@ Control Language="C#" 

        AutoEventWireup="true" 

        CodeBehind="EchoControl.ascx.cs" 

        Inherits="ControlsDemo.ControlTemplates.ControlsDemo.EchoControl" %>

Enter some text:

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

<asp:Button ID="Button1" runat="server" Text="Button" />

<asp:Label ID="Label1" runat="server" Visible="false"></asp:Label>

Because you can add markup for your control, you get the nice WYSIWYG designers for your control.  This allows you to drag items from the toolbox, such as a button, a label, and a text box. 

SharePoint Server Controls

A server control is a compiled control that renders on the server.  Where user controls derive from System.Web.UI.UserControl, a server control (also known as a custom control) typically derives from System.Web.UI.WebControl.  The main difference is that server controls do not have a corresponding .ASCX control.  For some scenarios, this can be highly beneficial because the page parser does not need to parse the .ASCX control.

Creating a server control is very easy.  In Visual Studio 2010, add a new ASP.NET Server Control item to your project from the Web group.

image

The generated template is just a suggestion, you can edit the class to suit your needs.  Here is a useful control for SharePoint developers that simply shows the name of the server that is currently processing the request.

using System;

using System.Web.UI.WebControls;

using System.Web.UI;

namespace ControlsDemo

{

    [ToolboxData("<{0}:ServerNameControl runat=server></{0}:ServerNameControl>")]

    public class ServerNameControl : WebControl

    {

        protected override void CreateChildControls()

        {

            Label l = new Label();

            l.Text = System.Environment.MachineName;

            Controls.Add(l);   

        }

    }

}