X509Store certStore = new X509Store(StoreLocation.CurrentUser);
        certStore.Open(OpenFlags.ReadOnly);
        var cert = GetCertificate();
        var signatureToken = GetSecurityToken(cert);
        RequestSoapContext.Security.Tokens.Add(signatureToken);
        MessageSignature sign = new MessageSignature(signatureToken);
        RequestSoapContext.Security.Elements.Add(sign);