S#harp体系结构映射多对多和ado.net数据服务:预期结果为单个资源,但找到了多个资源

我正在开发一个应用程序,通过ADO.NET数据服务从一个SQL server数据库(从遗留数据库迁移)读取数据,该数据库采用nHibernate和s#arp体系结构。我正在尝试映射多对多关系。我有一个错误类:

public class Error
{
    public virtual int ERROR_ID { get; set; }
    public virtual string ERROR_CODE { get; set; }
    public virtual string DESCRIPTION { get; set; }

    public virtual IList<ErrorGroup> GROUPS { get; protected set; }
}

public class ErrorGroup
{
    public virtual int ERROR_GROUP_ID {get; set;}
    public virtual string ERROR_GROUP_NAME { get; set; }
    public virtual string DESCRIPTION { get; set; }

    public virtual IList<Error> ERRORS { get; protected set; }
}

public class ErrorGroupOverride : IAutoMappingOverride<ErrorGroup>
{
    public void Override(AutoMapping<ErrorGroup> mapping)
    {
        mapping.Table("ERROR_GROUP");
        mapping.Id(x => x.ERROR_GROUP_ID, "ERROR_GROUP_ID");
        mapping.IgnoreProperty(x => x.Id);
        mapping.HasManyToMany<Error>(x => x.Error)
            .Table("ERROR_GROUP_LINK")
            .ParentKeyColumn("ERROR_GROUP_ID")
            .ChildKeyColumn("ERROR_ID").Inverse().AsBag();
    }
}

public class ErrorOverride : IAutoMappingOverride<Error>
{
    public void Override(AutoMapping<Error> mapping)
    {
        mapping.Table("ERROR");
        mapping.Id(x => x.ERROR_ID, "ERROR_ID");
        mapping.IgnoreProperty(x => x.Id);
        mapping.HasManyToMany<ErrorGroup>(x => x.GROUPS)
            .Table("ERROR_GROUP_LINK")
            .ParentKeyColumn("ERROR_ID")
            .ChildKeyColumn("ERROR_GROUP_ID").AsBag();
    }
}

当我在浏览器中查看数据服务时,如: http://localhost:1905/DataService.svc/Errors 它显示了没有问题的错误列表,并像 http://localhost:1905/DataService.svc/Errors(123)

问题 http://localhost:1905/DataService.svc/Errors(123)

The XML page cannot be displayed 
Cannot view XML input using XSL style sheet. Please correct the error and then click the Refresh button, or try again later. 
--------------------------------------------------------------------------------
Only one top level element is allowed in an XML document. Error processing resource 'http://localhost:1905/DataServic...
<error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">
-^

我查看源代码,然后 我得到了数据 . 但是,它有一个例外:

<error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">
  <code></code>
  <message xml:lang="en-US">An error occurred while processing this request.</message>
  <innererror xmlns="xmlns">
    <message>A single resource was expected for the result, but multiple resources were found.</message>

    <type>System.InvalidOperationException</type>
    <stacktrace>   at System.Data.Services.Serializers.Serializer.WriteRequest(IEnumerator queryResults, Boolean hasMoved)&#xD;
   at System.Data.Services.ResponseBodyWriter.Write(Stream stream)</stacktrace>
  </innererror>
</error>

A我错过了什么???这个错误是从哪里来的?