ASP.NET ASP.NET - User Controls Introduction of User Controls
Example
User controls are made for reusability across ASP.NET pages, similar to master pages. Instead of sharing base page layout, user controls share group of HTML/ASP.NET built-in server controls or a specific form layout, e.g. comment submission or guest notes.
A user control can contain both HTML controls and ASP.NET server controls, including client-side scripts.
The user controls usually include Control directive on top of its definition:
<%@ Control Language="C#" AutoEventWireup="True" CodeFile="UserControl.ascx.cs" %>
Like ASPX page, user controls consists of markups which can be associated with a code behind file to perform certain events and tasks, therefore all HTML tags available on ASPX page can be used on user controls except <html>, <body> and <form> tags.
Here is an example for simple user control markup:
<%-- UserControl.ascx --%>
<%@ Control Language="C#" AutoEventWireup="True" CodeFile="UserControl.ascx.cs" %>
<div>
<asp:Label ID="Label1" runat="server" />
<br />
<asp:Button ID="Button1" runat="server" Text="Click Here" OnClick="Button1_Click" />
</div>
Code-behind example:
// UserControl.ascx.cs
public partial class UserControl : System.Web.UI.UserControl
{
protected void Button1_Click(Object sender, EventArgs e)
{
Label1.Text = "Hello World!";
}
}
Before a user control inserted in ASPX page, Register directive should declared on top of the page referencing the user control with its source URL, tag name & tag prefix.
<%@ Register Src="UserControl.ascx" TagName="UserControl" TagPrefix="uc" %>
Afterwards, you can place user control inside ASPX page like ASP.NET built-in server control:
<uc:UserControl ID="UserControl1" runat="server" />
