Calling the UserControl Event from the WebForm



The main theme behind this article is give the clear idea about the event and the event handling in .NET.


An event is a message sent by an object to signal the occurrence of an action. This action caused by the user interaction such as button click,mouse click e.t.c.The Object that send the event is called the event sender. The object that receives the event and respond according to that is called the event receiver.

 Actually in communication between the sender and the receiver ,the sender does not know which method or object will receive the event it raises. The mediator between these two is called “Delegate”.

 A delegate is a class that can hold a reference to a method .The Delegate class has a signature and it can hold the reference only to the methods that match to its signature.
Normally I found the requirement to save the main page data in the user control button click which led me to write this article.
Here I have taken a user control which contains a text box and button. The following the design code given below

 Code design:

 <asp:TextBox ID="txtbx" runat="server">asp:TextBox>
<asp:Button ID="btn" runat="server" Text="Click Me" OnClick="btn_Click" />

 Code Behind:

   On WebUserControl.ascx.cs I have written simple delegate and event handler as shown below,
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

 public partial class UserControls_TestControl : System.Web.UI.UserControl
{
     public String Value { get; set; }
    public delegate void OnButtonClick(string value, int count);
    public event OnButtonClick btnHandler;

     protected void Page_Load(object sender, EventArgs e)
    {

     }
    protected void btn_Click(object sender, EventArgs e)
    {
         if (btnHandler != null)
        {
             btnHandler(string.Empty, 0);
            // Write some text to output
            Response.Write("User Controls Button Click
");
            txtbx.Text = this.Value;
        }
    }
}

 Here in the above code it first checks the  btnHandleris null or not and raising the event by passing arguments.You can pass as many arguments as you want.But you need to change the public delegate void OnButtonClick(string value, int count) and btnHandler(string.Empty,0) lines for changing number of arguments.
Here I have taken a main page which comprises of textbox .I have used this user control in the main page .When the click this button of the user control I need to set the Text box value to the same of the text box in the main page.
TestPage.aspx:

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>title>
head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:TextBox runat="server" ID="txtbx" /><br />
        <br />
        <UC:UControl ID="ucTest" runat="server" />
    div>
    form>
body>
html>


The Code behind of this TestPage.aspx.cs is given below:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

 public partial class Test_Page : System.Web.UI.Page
{

     protected void Page_Load(object sender, EventArgs e)
    {
        ucTest.btnHandler += new UserControls_TestControl.OnButtonClick(ucTest_btnHandler);
     }

     void ucTest_btnHandler(string value, int count)
    {
        value = txtbx.Text;
        ucTest.Value = value;
        Response.Write("Main Page Event
Selected Value: " + value + "
");
    }

     protected void btn_Click(object sender, EventArgs e)
    {
    }
}

 The user control contains one button. When user click on this button I will call a method on main page using delegate.
The screen shot are given below to show the passing the Main Page Text box value to the User Control

The Final Output Screen Shot is given below


 Now when you run the application and clicks on button you can see that when user click on button the user control raise the click event and calls the  ucTest.btnHandler(string Value,int count) method on main page.
The Source Code can be downloaded from here.

 Happy Coding:-)

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