var hashid = new Hashids("123456789");
int id = hashid.DecodeSingle("NkK9");

var hashid = new Hashids("123456789");

try
{
    int id = hashid.DecodeSingle("NkK9");
}
catch (MultipleResultsException)
{
    //Handle exception when the hash returns more than one id.
}

int id;

if (hashid.TryDecodeSingle("NkK9,NkK9", out id))
{
   Console.WriteLine(id.ToString());
}
else
{
   Console.WriteLine("Invalid Id");
}