To access the Master Page’s methods or properties from a content page, reference Master Page through the Page.Master property. This property returns an object of type, so you’ll need to explicitly cast it to the appropriate type before calling its methods or referencing its properties. Alternatively, you can set the @MasterType directive, which adds a property to the auto-generated ASP.NET code-behind class code-named Master that is a strongly-typed reference to the specified Master Page.
The following markup in the .aspx file for the content page spells out the Master Page type:
<%@ MasterType VirtualPath="~/MasterPage.master" %>
To illustrate this, imagine that we had a DropDownList on Master Page. When its selected index changes, we want to notify the content page of the change to update its display accordingly. Start by creating a DropDownList named Color in Master Page that lists various colours (red, green, etc.) and then create an event handler for this DropDownList’s SelectedIndexChanged event. Next, we need to define an event for Master Page, specifying the event handler signature. The event handler signature specifies what input parameters are passed to the event handler. For this example, let’s pass the selected DropDownList item’s Text and Value property values. Therefore, we can use the CommandEventHandler delegate, which passes a CommandEventArgs object to the event handler, which includes CommandName and CommandArgument properties that we can use to hold the selected ListItem's Text and Value property values.
To define an event named MoodChanged for Master Page that uses the CommandEventHandler delegate, use the following syntax:
[Masterpage.aspx]
<%@ 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 runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:DropDownList ID="Color" runat="server" OnSelectedIndexChanged="Color_SelectedIndexChanged"
AutoPostBack="True">
<asp:ListItem>Red</asp:ListItem>
<asp:ListItem Value="Green">Green</asp:ListItem>
<asp:ListItem Value="Blue">Blue</asp:ListItem>
<asp:ListItem Value="Yellow">Yellow</asp:ListItem>
</asp:DropDownList>
<asp:Panel ID="Panel1" runat="Server">
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Login" />
</asp:Panel>
<asp:ContentPlaceHolder ID="ContentPlaceHolder1" runat="server">
</asp:ContentPlaceHolder>
</div>
</form>
</body>
</html>
[Master Page Code-Behind]
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 MasterPage : System.Web.UI.MasterPage
{
public event CommandEventHandler ColorChanged;
public event CommandEventHandler MoodChanged;
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Color_SelectedIndexChanged(object sender, EventArgs e)
{
if (Color.SelectedIndex != 0 && ColorChanged != null)
ColorChanged(this, new CommandEventArgs(Color.SelectedItem.Text, Color.SelectedValue));
}
protected void Button1_Click(object sender, EventArgs e)
{
if (TextBox1.Text != "" && MoodChanged != null)
MoodChanged(this, new CommandEventArgs(TextBox1.Text, TextBox2.Text));
}
}
[Content Page] [Default.aspx]
<%@ Page Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true"
CodeFile="Default.aspx.cs" Inherits="_Default" Title="Untitled Page" %>
<%@ MasterType VirtualPath="~/MasterPage.master" %>
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
<asp:Label ID="ColorChnage" runat="Server"></asp:Label><br />
<asp:Label ID="Label1" runat="Server"></asp:Label>
</asp:Content>
[Code-Behind]
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 Page_Init(object sender, EventArgs e)
{
// Wire up the event (MoodChanged) to the event handler (MoodChangedFromMasterPage)
Master.ColorChanged += new CommandEventHandler(ColorChangedFromMasterPage);
Master.MoodChanged += new CommandEventHandler(MoodChangedFromMasterPage);
}
private void ColorChangedFromMasterPage(object sender, CommandEventArgs e)
{
string moodText = e.CommandName;
string moodValue = e.CommandArgument.ToString();
ColorChnage.Text = String.Format("You have selected color {0}, which has a value of {1}...", moodText, moodValue);
Label1.Visible = false;
ColorChnage.Visible = true;
}
private void MoodChangedFromMasterPage(object sender, CommandEventArgs e)
{
string moodText = e.CommandName;
string moodValue = e.CommandArgument.ToString();
Label1.Text = String.Format("You have enterd user name {0}, which has a password of {1}...", moodText, moodValue);
((Panel)Master.FindControl("Panel1")).Visible = false;
Label1.Visible = true;
ColorChnage.Visible = false;
}
}