How to make the Default focus in content page from master page

Question

I have masterpage with content place holder. i have contentpage which is using master page . in all my content page i need to default focus on the text b

Answer 1

Control masterC = 
Page.Master.FindControl("ContentPlaceHolder1");
    TextBox TextBox1 = 
masterC.FindControl("TextBoxUsername") as TextBox;

TextBox1.Focus();