How to access content page controls from master page in asp.net

Question

it is very easy to access master page control from content page like

protected void Page_Load(object sender, EventArgs e)
{
    // content page load event
          


        

Answer 1

C# code within Site.Master:

Code within Site.Master.cs:

public partial class SiteMaster : MasterPage
{
    protected void Page_Load(object sender, EventArgs e)
    {          
        ToolkitScriptManager1.RegisterPostBackControl(this.MainContent.FindControl("btnOnDefaultPage"));            
    }
}

This is an example how a client control on the Default.aspx is referenced from a Site.Master.cs