C# - Validate Dropdownlist Selectedvalue Against A List From Static Property?

I am using javascript to validate user input on my aspx page. I am easily able to validate textboxes and dropdown list for differenet scenarios.

Now, on one of my dropdown lists (for country), I need to check if it is an allowed country or not for a particular service. I have stored the valid country list in a static property. Is there a way to validate my dropdownlist selected value against that static property?

function validateService(source, args)
{
var country = document.getElementById('<%= ddDestCountry.ClientID %>');
var service = document.getElementById('<%= ddService.ClientID %>');
// Get allowed country list from my static class
var countryList = document.getElementById('<%= StaticProperties.EUCountryList %>');
if (service.value == "P")
{
// I want to do something like this
if (!countrylist.Contains(country.value))
{
args.IsValid = false;
}
else {
args.IsValid = true;
}
}
return;
}

Update(Additional Information): The static property is read-only so it cannot be tampered with from the page.