TextBox not Displays Value from Codebehind....

<asp:TextBox ID="txtTest" runat ="server" ></asp:TextBox>
<asp:Label ID="lbltest" runat="server"></asp:Label>
Page_Load()
---------------
txtTest.text="ok";
if (string.IsNullOrEmpty(txtTest.Text))
lbltest.Text = "";
else
lbltest.Text = txtTest.Text;

Output
----------
lbltest----------  ok
txtTest---------  EmptyValue

Why TextBox showing empty value but i have assigned value.
...