gistfile1.cs

protected override bool OnServerValidate(string value)
{
    var validatorSettings = GetValidatorSettingsItem();
    Sitecore.Diagnostics.Assert.IsNotNull(validatorSettings, ValidationSettingsItemMissingMessage + ValidationSettingsItem);

    // obtain an instance of the SimpleForm
    var form = WebUtil.GetParent<SimpleForm>(this);

    // obtain an instance of our field
    var countryField = (CountryDropDownList)WebUtil.FindFirstOrDefault(form, c => c is CountryDropDownList && string.Compare((c as CountryDropDownList).Result.FieldName, validatorSettings.CountryFieldName) == 0);
    if (countryField != null)
    {
        // is the field required?
        bool isRequired = countryField.Requred.Any();
                
        // continue handling further processing here...
    }

    return base.OnServerValidate(value);
}