CoreWCF接收MTOM格式XOP:Include附件的实现难题

我正在使用.NET 6和CoreWCF开发SOAP服务，需要接收供应商指定格式的SOAP消息，该消息包含元数据及通过MTOM发送的文件附件。

当我将请求类的属性设为字节数组时，可正常接收以下格式的文件：

<parent>
  <child>
    <attachment>cid:mycontentid</attachment>
  </child>
</parent>

但供应商采用引用http://www.w3.org/2004/08/xop/include命名空间的<xop:Include>元素发送文件，格式如下：

<parent xmlns:xop="http://www.w3.org/2004/08/xop/include">
  <child>
    <attachment>
      <xop:Include href="cid:mycontentid"/>
    </attachment>
  </child>
</parent>

尝试接收该格式文件时，无论如何设置，对应属性始终为null。我当前的Attachment/Include类代码如下：

public class Attachment
{
  //WSDL looks right, but deserializes to null
  //[XmlElement(ElementName = "Include", Namespace="http://www.w3.org/2004/08/xop/include")]
  //public Include Include { get; set; }
  
  //WSDL looks right, but deserializes to null
  //[XmlElement(ElementName = "Include", Namespace="http://www.w3.org/2004/08/xop/include")]
  //public byte[] Include { get; set; }

  //WSDL looks wrong, only accepts <attachment>cid:...<attachment>
  public byte[] Include { get; set; }
}

public class Include 
{
  [XmlAttribute(AttributeName="href", Namespace="http://www.w3.org/2004/08/xop/include")]
  public byte[] Href { get;set; }
}

相关文档较少，我陷入困境，请问如何用CoreWCF（或原WCF，我可适配）实现该需求？

1. 修正类结构与序列化属性 #

调整你的实体类，让序列化器正确识别XOP命名空间的Include元素，注意href是字符串类型（仅为附件的cid引用，不是字节数组）：

using System.Xml.Serialization;

public class Attachment
{
    [XmlElement(ElementName = "Include", Namespace = "http://www.w3.org/2004/08/xop/include")]
    public XopInclude Include { get; set; }
}

public class XopInclude
{
    [XmlAttribute(AttributeName = "href", Namespace = "http://www.w3.org/2004/08/xop/include")]
    public string Href { get; set; }
}

2. 启用MTOM绑定配置 #

CoreWCF必须启用MTOM才能解析XOP格式的请求，在代码或配置文件中设置绑定：

var binding = new BasicHttpBinding(BasicHttpSecurityMode.None);
binding.MessageEncoding = WSMessageEncoding.Mtom;
// 根据业务需求调整大小限制
binding.MaxReceivedMessageSize = 10485760; // 10MB
binding.ReaderQuotas.MaxArrayLength = 10485760;

3. 提取附件字节数组 #

如果需要直接获取附件的二进制内容，可在服务方法中通过OperationContext手动提取匹配的附件：

public void ProcessRequest(MyRequest request)
{
    var requestMessage = OperationContext.Current.RequestContext.RequestMessage;
    foreach (var attachment in requestMessage.Attachments)
    {
        // 去除cid前缀，匹配附件ID
        var targetCid = request.Child.Attachment.Include.Href.Replace("cid:", "");
        if (attachment.ContentId == targetCid)
        {
            using var stream = new MemoryStream();
            attachment.ContentStream.CopyTo(stream);
            byte[] fileBytes = stream.ToArray();
            // 处理文件内容
        }
    }
}

关键注意事项 #

• 不要将href属性定义为byte[]，它只是MTOM附件的标识字符串。
• 必须确保服务绑定启用MTOM，否则CoreWCF无法识别XOP格式的请求结构。
• 修正后的类结构会生成符合标准的WSDL，确保与供应商的请求契约匹配。

内容的提问来源于stack exchange，提问作者Chris Disley