Have this in your web config file
<configuration>
<system.Web>
<pages masterPageFile="your master name.master" />
</system.Web>
</configuration>
the
<system.web></system.web>
tag may be already exists, then only need to add the pages tag inside of it. Don't define a new System.Web tag
The above one is for .Net framework 4, some of the lower version may have this syntax
<pages master="your master.master"></pages>
Can have a master page inherited from a class inherited from master page.
In case of all the pages has to use a common base class, alternatively can have a class with extension methods for the
Page
class.
Example...
public static class PageExtensionMethods
{
public static string GetDefaultCopyRightString(this Page globalPage)
{
return "Copy Right Reserved Test Company , 2011";
}
}
Now you can call this method from any page i.e in all pages..example..
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string copyRight=this.GetDefaultCopyRightString();
}
}