protected void Category_SelectedIndexChanged(object sender, EventArgs e) { int MainCatId = Convert.ToInt32(Category.SelectedItem.Value); SqlCommand cmd = new SqlCommand("select * from SubCategory where MainCatId ='" + Category.SelectedItem.Value + "' ", con); SqlDataAdapter adp = new SqlDataAdapter(cmd); DataTable dt = new DataTable(); adp.Fill(dt); if (dt.Rows.Count != 0) { Sub.DataSource = dt; Sub.DataTextField = "SubCatName"; Sub.DataValueField = "SubCatId"; Sub.DataBind(); Sub.Items.Insert(0, new ListItem("-Select-", "0")); Sub.Enabled = true; } }