ServiceCredentials Class

public class MyServiceCredentials : ServiceCredentials
{
    X509Certificate2 additionalCertificate;

    public MyServiceCredentials()
    {
    }

    protected MyServiceCredentials(MyServiceCredentials other)
        : base(other)
    {
        this.additionalCertificate = other.additionalCertificate;
    }

    public X509Certificate2 AdditionalCertificate
    {
        get
        {
            return this.additionalCertificate;
        }
        set
        {
            if (value == null)
            {
                throw new ArgumentNullException("value");
            }
            this.additionalCertificate = value;
        }
    }

    public override SecurityTokenManager CreateSecurityTokenManager()
    {
        return base.CreateSecurityTokenManager();
    }

    protected override ServiceCredentials CloneCore()
    {
        return new MyServiceCredentials(this);
    }
}