ArtifactResolve重复签名及ArtifactBinding空引用异常问题求助

问题1：PostBinding绑定后XML出现重复Signature节点 #

创建ArtifactResolve对象并通过Saml2PostBinding绑定后，生成的XML文档包含两个Signature节点，疑似对象被签名了两次。相关代码如下：

Saml2Configuration samlConfig = new Saml2Configuration
{
    Issuer = "issuer.com",
    SigningCertificate = cert,
    SignatureAlgorithm = "mysignalg",
    SignAuthnRequest = true,
};

Saml2ArtifactResolve artifactResolve = new Saml2ArtifactResolve(samlConfig)
{
    IdAsString = "_" + Guid.NewGuid().ToString("N"),
    Artifact = artifact
};

artifactResolve.Validate();
Saml2PostBinding binding = new Saml2PostBinding();
return binding.Bind(artifactResolve);

问题2：使用ArtifactBinding时触发空引用异常 #

改用Saml2ArtifactBinding绑定ArtifactResolve时，出现空引用异常。相关代码如下：

Saml2Configuration samlConfig = new Saml2Configuration
{
    Issuer = "msomething.nl",
    SigningCertificate = cert,
    SignatureAlgorithm = SingatureAlgorithm,
    SignAuthnRequest = true
};

Saml2ArtifactResolve artifactResolve = new Saml2ArtifactResolve(samlConfig)
{
    IdAsString = "_" + Guid.NewGuid().ToString("N"),
    Artifact = artifact,
    Destination = new Uri("http://mydestination"),
};

artifactResolve.Validate();
Saml2ArtifactBinding binding = new Saml2ArtifactBinding();
binding.RelayState = Guid.NewGuid().ToString();

return binding.Bind(artifactResolve);

内容的提问来源于stack exchange，提问作者TheFunOne