Set Page Programmatically

The page title in SharePoint is located in the content place holder called PlaceHolderPageTitle.

You can change it by referencing the place holder and setting a value in. 

ContentPlaceHolder cp= (ContentPlaceHolder)Page.Master.FindControl("PlaceHolderPageTitle");

cp.Controls.Clear();
cp.Controls.Add(new LiteralControl("The Title here"));

QED