private void cboProjections_Validating(object sender, CancelEventArgs e)
{
bool listSelected = radioSRIDFromList.Checked;
bool valueInList = cboProjections.SelectedIndex != -1;
string errorMessage = string.Empty;
//if our radio button is selected.
//if the value is not in the list
if (listSelected && !valueInList)
{
errorMessage = "Unknown SRID";
}
this.errorProvider1.SetError(cboProjections, errorMessage);
}