Accessing Master page functions from content page we must include a MasterType directive at the top of the Content page ASPX file:
<%@ MasterType virtualpath="~/DetailsMaster.master" %>
In DetailsMaster.master.cs page
public void SavePageData()
// function definition
After place the MasterType directive is in place in the Content page, then public functions in the Master page are available to the Content page code.
//Call the SavePageData function from the Master page
I hope it will helpfull for other developer.