Master Page Related

//TO find Controls from the ContentPlaceHolder
ContentPlaceHolder mpContentPlaceHolder;
TextBox mpTextBox;
mpContentPlaceHolder =(ContentPlaceHolder)Master.FindControl("ContentPlaceHolder1");
if(mpContentPlaceHolder != null)
{
mpTextBox =
(TextBox) mpContentPlaceHolder.FindControl("TextBox1");
if(mpTextBox != null)
{
mpTextBox.Text = "TextBox found!";
}
}