clicking the combobox message will appear to the user

Hi Sarika,

Make sure AutoPostBack property of the dropdownlist to True


Thanks

try this. hope it helps.



        protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (ListBox1.SelectedItem == null)
            {
                MessageBoxShow(this, "Please select listitem first.");
            }
        }

         private void MessageBoxShow(Page page, string message)
        {
            Literal ltr = new Literal();
            ltr.Text = @"";
            page.Controls.Add(ltr);
        }

Sarika