您的网页上使用一个ScriptManager？如果是这样，请尝试以下操作：

 公共无效SetInputFocus（）
{
    文本框TBOX = this.loginForm.FindControl（用户名）的文本框;
    如果（TBOX！= NULL）
    {
       ScriptManager.GetCurrent（this.Page）.SETFOCUS（TBOX）;
    }
}
 

更新：之前从未使用过的多视点，但试试这个：

 保护无效MultiView1_ActiveViewChanged（对象发件人，EventArgs的发送）
{
   SetInputFocus（）;
}
 

I am trying to set the focus to the user name TextBox which is inside an ASP.NET Login control.

I have tried to do this a couple of ways but none seem to be working. The page is loading but not going to the control.

Here is the code I've tried.

SetFocus(this.loginForm.FindControl("UserName"));

And

TextBox tbox = (TextBox)this.loginForm.FindControl("UserName");
if (tbox != null)
{    
  tbox.Focus();
} // if

Are you using a ScriptManager on the Page? If so, try the following:

public void SetInputFocus()
{
    TextBox tbox = this.loginForm.FindControl("UserName") as TextBox;
    if (tbox != null)
    {
       ScriptManager.GetCurrent(this.Page).SetFocus(tbox);
    }
}

Update: Never used a multiview before, but try this:

protected void MultiView1_ActiveViewChanged(object sender, EventArgs e)
{
   SetInputFocus();
}