does not appear password value in

 I use this <asp:TextBox runat="server" ID="txt_Pass" TextMode="Password" Width="170px"></asp:TextBox>
text box for  password and i want to display the password in this text box.
So i select from database and assign into textbox.text but no text doesn't appear.
         con_open();
        cmd.CommandText = "Select * From [tblstaff] where [uid]=" + this.ddl_UID.SelectedValue + ";";
        DReader = cmd.ExecuteReader();
        DReader.Read();
        txt_UName.Text = DReader.GetValue(1).ToString();
        txt_Pass.Text = DReader.GetValue(2).ToString();
        txt_CPass.Text = DReader.GetValue(3).To ...