Adding attributes to the <body> tag when using Master Pages

Chuck Bevitt

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30 Jul 20072 min read

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Accessing the Master Page <body> tag from an ASP.NET Content page

Problem

If you are using Master Pages in an ASP.NET application and you need to add an attribute to the <BODY> tag from a Content Page -- for instance, to set a client script function for the onload event of the page -- you will find that you can't do it directly because the <BODY> tag is in the Master Page, not in your Content Page.

Solution

Make the <BODY> tag on the Master Page a public property, so you can access it from any Content Page. First, promote the <BODY> tag in the Master Page to an ASP.NET server control. Change:

ASP.NET

<BODY>

to:

ASP.NET

<BODY id="MasterPageBodyTag" runat="server">

Now that the body tag is a server control, you can configure access to it as a public property in the Master Page code behind file:

using System.Web.UI.HtmlControls;
public partial class MyMasterPage : System.Web.UI.MasterPage
{
    public HtmlGenericControl BodyTag
    {
        get
        {
            return MasterPageBodyTag;
        }
        set
        {
            MasterPageBodyTag = value;
        }
    }
...

Note that the MasterPageBodyTag server control is of type System.Web.UI.HtmlControls.HtmlGenericControl. To demonstrate this, just set a breakpoint in the Page_Load function in the code behind file, run the ASP.NET project in debug mode to that point, and execute ?MasterPageBodyTag.GetType().ToString() in the Immediate Window. To use this property from a Content Page, first declare the type of your Master Page in your Content Page's ASPX file:

ASP.NET

<%@ MasterType TypeName="MyMasterPage" %>

Then somewhere in your Content Page's code behind file, use the Master Page's BodyTag property to add an attribute to the <BODY> tag:

protected void Page_Load(object sender, EventArgs e)
{
    Master.BodyTag.Attributes.Add("onload", "SayHello()");
...

This example, of course, assumes that there is a SayHello() client script in this Content Page. Running the application to the Content Page and then viewing the source code in the browser will show that the onload="SayHello()" attribute was added to the <BODY> tag. This technique should work for any HTML tag in the Master Page that you wish to access from a Content Page.

History

28 June, 2007 -- Original version posted
30 June, 2007 -- Article moved to main CodeProject.com article base
30 July, 2007 -- Article edited

License

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Written By

Chuck Bevitt

United States