GetAnyPublicKey

public static AsymmetricAlgorithm GetAnyPublicKey(this X509Certificate2 c)
{
    AsymmetricAlgorithm a;

    a = c.GetRSAPublicKey();
    if (a != null)
        return a;

    a = c.GetDSAPublicKey();
    if (a != null)
        return a;

    a = c.GetECDsaPublicKey();
    if (a != null)
        return a;

    throw new NotSupportedException(SecurityResources.GetResourceString("NotSupported_KeyAlgorithm"));
}