Please refer below code.
ContentPlaceHolder cp = this.Master.Master.FindControl("ContentPlaceHolder2") as ContentPlaceHolder;
cp.FindControl("TopPartCTL1").Visible = true;
I hope above code will help you.
ContentPlaceHolder cp = this.Master.Master.FindControl("ContentPlaceHolder2") as ContentPlaceHolder;
cp.FindControl("TopPartCTL1").Visible = true;
I hope above code will help you.