//this event fire when user don't focus on it
private void txtname_Validated(object sender, EventArgs e)
{
BL.Product product = new BL.Product();
if (product.Check_Product_Name(txtname.Text)) { MessageBox.Show("هذا المنتج موجود بالفعل", "تنبيه", MessageBoxButtons.OK, MessageBoxIcon.Warning);
txtname.Focus();
txtname.SelectionStart = 0;
txtname.SelectionLength = txtname.TextLength;
}
}