Input string was not in a correct format.

Hi 
my code is
Label1.Font.Name = dp_fontName.SelectedItem.Text;
Label1.Font.Size = new FontUnit(Convert.ToInt32(dp_fontSize.SelectedValue));
Label1.ForeColor = System.Drawing.Color.FromName(dp_fontColor.SelectedItem.Text);
when i run the code. the dropdownlist will be display and also font name and font size,color. i  use required field validator to validate the control. its does,t work. i did.t select any dropdown its does't show error message on validator and also i got input string was not ina correct format.
 can you help any one.......


...