Using FindControl with a MasterPage in ASP.NET & C#

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Using FindControl with a MasterPage in ASP.NET & C#

ASP.NET Controls Tutorial

This tutorials shows how we can use the FindControl method to reference controls in naming containers. C# version.

Referencing controls in ASP.NET is usually straight-forward. However, because of its complexity and adding new features such as MasterPages, the ease in referencing controls gets a little harder. Because such things as a MasterPage are naming containers, we have to reference these as well, when trying to reference a control within in. For example, if we have a label within a MasterPage, and we want to reference this label from a Content Page, then we would have to use the FindControl method of the MasterPage. This tutorial will show how we can do this. We will start by creating a Master Page:

<%@ Master Language="C#" AutoEventWireup="true" CodeFile="MasterPage.master.cs" Inherits="MasterPage" %>

<!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>Using FindControl with MasterPages in ASP.NET 2.0 and C#.NET</title>

</head>
<body>

<form id="form1" runat="server">

<div style="width:50%;border:1px solid black;">This text is in the MasterPage.<br />
<asp:Label ID="Label1" runat="server"></asp:Label><br />
This text is in the MasterPage.<br /></div>
<br />

<asp:contentplaceholder id="ContentPlaceHolder1" runat="server">

</asp:contentplaceholder>

</form>

</body>
</html>

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Then we have the Content Page:

<%@ Page Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" Title="Untitled Page" %>
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">

Type in text and then click button to display text in a Label that is in the MasterPage.<br />
This is done using FindControl.<br />
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Submit" /><br />
<br />
Choose an item from the below list and it will be displayed in the Label that is
in the MasterPage.<br />
This is done using FindControl.<br />
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">

<asp:ListItem>Item 1</asp:ListItem>
<asp:ListItem>Item 2</asp:ListItem>
<asp:ListItem>Item 3</asp:ListItem>

</asp:DropDownList>

</asp:Content>

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The code-behind will look something like this:

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 _Default : System.Web.UI.Page
{

protected void Page_Load(object sender, EventArgs e)
{

}

protected void Button1_Click(object sender, EventArgs e)
{

if (TextBox1.Text != "")
{

Label Label1 = (Label)Master.FindControl("Label1");
Label1.Text = "<b>The text you entered was: " + TextBox1.Text + ".</b>";

}

}

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{

Label Label1 = (Label)Master.FindControl("Label1");
Label1.Text = "<b>You chose <u>" + DropDownList1.SelectedValue + "</u> from the dropdown menu.</b>";

}

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