Introduction: In this
Article we will discuss about how to create and raise the event for user control
which is being used on the application. So as much as we know about the delegate
which is normally known as function pointer in C# by using a delegate we have to
raise an event to the user control which will show the content of the event on
the main page or .aspx page. Here I am going to show you a simple example of
delegate. Here I have one user control and one .aspx page. In which user control
have a button only and .aspx page have a label and a dropdown list whenever we
select any value from the drop down list and click on the button it will show
the name of content at the main page. here we will call a method on main page
using delegate.
Now we are going to make the
project let us see how it is created follow the steps given below.
Step 1:
-
Open the Visual Studio 2010.
-
Open the web site application.
-
Give any name.
Step 2: Now add a new
folder to the site name as controls
-
Add new item name as Web User
Control to that folder.
-
Click OK.
-
It will look like as into the
website shown below.
Step 3: Now we are going to
drag and drop a button control on the Controls/WebUserControl.ascx.
We can add the button control
to the user control by writing the code given below to the source page of
Controls/WebUserControl.ascx file which is given below.
Code:
<%@
Control Language="C#"
AutoEventWireup="true"
CodeFile="WebUserControl.ascx.cs"
Inherits="Controls_WebUserControl"
%>
<asp:Button
ID="Button1"
runat="server"
Text="Click me!"
BackColor="#9999FF"
BorderColor="Fuchsia"
BorderStyle="Groove"
onclick="Button1_Click"
/>
Step 4: Further you have to
write the code in the Controls/WebUserControl.ascx.cs file of the user control.
Code :
using
System;
using
System.Collections.Generic;
using
System.Linq;
using
System.Web;
using
System.Web.UI;
using
System.Web.UI.WebControls;
public
partial class
Controls_WebUserControl : System.Web.UI.UserControl
{
// Delegate declaration
public
delegate void
btn_Click(string str);
// Event declaration
public event
btn_Click btnHandler;
// Page load
protected void
Page_Load(object sender,
EventArgs e)
{
}
protected void
Button1_Click(object sender,
EventArgs e)
{
// Check if event is null
if (btnHandler !=
null)
btnHandler(string.Empty);
// Write some text to output
Response.Write("User Control's Button
Click <BR/>");
}
}
Code Description:
In the above code we have written
simple a delegate and an event handler and on click event of the button we have
to check whether the event handler is empty or not if it have any argument then
it will raise the event.
Step 5:
Now we have to open the source file of default.aspx and write the code given
below.
Code :
<%@
Page Title="Home
Page" Language="C#"
MasterPageFile="~/Site.master"
AutoEventWireup="true"
CodeFile="Default.aspx.cs"
Inherits="_Default"
%>
<%@ Register
Src="~/Controls/WebUserControl.ascx"
TagName="WebUserControl"
TagPrefix="BC"
%>
<asp:Content
ID="HeaderContent" runat="server"
ContentPlaceHolderID="HeadContent">
</asp:Content>
<asp:Content
ID="BodyContent" runat="server"
ContentPlaceHolderID="MainContent">
<h2>
Welcome to ASP.NET!
</h2>
<p>
<asp:Label
ID="lbl"
Text=" Main Page Content
: " runat="server"
BackColor="#0099FF"></asp:Label>
<asp:DropDownList
ID="dropdownselect"
runat="server"
BackColor="#FFCC99"
Height="59px"
Width="105px">
<asp:ListItem>Amit</asp:ListItem>
<asp:ListItem>Alok</asp:ListItem>
<asp:ListItem>Rajesh</asp:ListItem>
<asp:ListItem>Manoj</asp:ListItem>
<asp:ListItem>Manish</asp:ListItem>
</asp:DropDownList>
<br
/>
<br
/>
<BC:WebUserControl
ID="WebUserControl1"
runat="server"
/>
</p>
</asp:Content>
Code
Description:
Here we have add only one label and a dropdown list to the default page. Further
we are using the user control by adding the directive to the source file of
default.aspx.
Step 6:
In this step we will write the code for the default.aspx.cs page which is given below.
Code :
using System;
using
System.Collections.Generic;
using
System.Linq;
using System.Web;
using
System.Web.UI;
using
System.Web.UI.WebControls;
public
partial class
_Default : System.Web.UI.Page
{
protected void
Page_Load(object sender,
EventArgs e)
{
WebUserControl1.btnHandler += new
Controls_WebUserControl.btn_Click(WebUserControl1_btnHandler);
}
void WebUserControl1_btnHandler(string
str)
{
Response.Write("Main Page
Event<BR/>Selected Value of drop down list is: " + dropdownselect.SelectedItem.Text
+ "<BR/>");
}
}
Code Description:
The above code will declare and define event of user control, when user Clicks
on button which is inside user control. The given below event raised as I have
called raised that event on button click.
Step 7:
Now build the application by click on build option.
Before Run:
![Before Run]()
Step 8:
Further we have to run the application by pressing F5.
After Run: Select the name from the drop down list.
![Select Item]()
Output :
After selection Click the button user control it will raise an event which is
shown in the output given below.
![Output]()