Login_click()
{
  Responese.Redirect("newPage.aspx");
}

Login_click()
{
//... validate the user and get the user name
Response.Redirect(username +".sample.com");
}

我还没有测试过，但我想您已经尝试过了

Ive not tested this but I guess you''ve already tried

这对我来说很有效

this worked for me though

string name = "plus";
            string url = "http://www."+name+".google.com";
            Response.Redirect(url);

如果要在本地主机中重定向，请使用

If you want to redirect in localhost then use

Server.MapPath(url)