VS2012中Database-first开发Web应用，老是报错序列化错误，真的求解！！

在下第一次发帖，各位多多包涵~
我最近在学习Entity Framework框架

同时在做一个网上超市的小作业，要求
数据库已经存在
数据库： Microsoft SQL Server 2008
开发工具：VS2012
模式架构：MVC4 & Entity Framework Database-First

我现在已经向工程中添加了ADO.NET Entity Data Model，工程自动生成了edmx文件，然后我在Controller类当中添加了一个名为“BlankController”用来测试的ApiController，代码如下：



using System;

using System.Collections.Generic;

using System.Linq;

using System.Net;

using System.Net.Http;

using System.Web.Http;



using MySuperMarket.Models;



namespace MySuperMarket.Controllers

{

    public class BlankController : ApiController

    {

        public OnlineMarketEntities db = new OnlineMarketEntities();



        public IEnumerable<Client> GetClients()

        {

            return db.Client.Where(p=>p.CLID != 0);

        }

    }

}

之后我便开始运行项目，但是出来之后结果是这样的：



This XML file does not appear to have any style information associated with it. 

The document tree is shown below.

<Error>

  <Message>

    An error has occurred.

  </Message>

  <ExceptionMessage>

    The 'ObjectContent`1' type failed to serialize the response body for content

    type 'application/xml; charset=utf-8'.

  </ExceptionMessage>

  <ExceptionType>

    System.InvalidOperationException

  </ExceptionType>

  <StackTrace/>

  <InnerException>

    <Message>

      An error has occurred.

    </Message>

    <ExceptionMessage>

      不应为数据协定名称为“Client_8258663FD2AFC77B2A97525EB9CA5AC173CC75D31938

      FEB3D9C02506ECFB9F13:http://schemas.datacontract.org/2004/07/System.Data.

      Entity.DynamicProxies”的类型“System.Data.Entity.DynamicProxies.Client_8

      258663FD2AFC77B2A97525EB9CA5AC173CC75D31938FEB3D9C02506ECFB9F13”。请考虑使

      用 DataContractResolver，或将任何未知类型以静态方式添加到已知类型的列表。例

      如，可以使用 KnownTypeAttribute 特性，或者将未知类型添加到传递给 

      DataContractSerializer 的已知类型列表。

    </ExceptionMessage>

    <ExceptionType>

      System.Runtime.Serialization.SerializationException

    </ExceptionType>

    <StackTrace>

      在 System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeAn

      dVerifyType(DataContract dataContract, XmlWriterDelegator xmlWriter, 

      Object obj, Boolean verifyKnownType, RuntimeTypeHandle declaredTypeHandle,

      Type declaredType) 在 System.Runtime.Serialization.

      XmlObjectSerializerWriteContext.SerializeWithXsiType

     (XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle  

      objectTypeHandle, Type objectType, Int32 declaredTypeID, 

      RuntimeTypeHandle declaredTypeHandle, Type declaredType) 在 

      System.Runtime.Serialization.XmlObjectSerializerWriteContext.

      InternalSerialize(XmlWriterDelegator xmlWriter, Object obj, Boolean 

      isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, 

      RuntimeTypeHandle declaredTypeHandle) 在 

      WriteArrayOfClientToXml(XmlWriterDelegator , Object , 

      XmlObjectSerializerWriteContext , CollectionDataContract ) 在 

      System.Runtime.Serialization.CollectionDataContract.WriteXmlValue

      (XmlWriterDelegator xmlWriter, Object obj, XmlObjectSerializerWriteContext 

      context) 在 System.Runtime.Serialization.XmlObjectSerializerWriteContext.

      WriteDataContractValue(DataContract dataContract, 

      XmlWriterDelegator xmlWriter, Object obj, 

      RuntimeTypeHandle declaredTypeHandle) 在 

      System.Runtime.Serialization.XmlObjectSerializerWriteContext.

      SerializeAndVerifyType(DataContract dataContract, 

      XmlWriterDelegator xmlWriter, Object obj, Boolean verifyKnownType, 

      RuntimeTypeHandle declaredTypeHandle, Type declaredType) 在 

      System.Runtime.Serialization.XmlObjectSerializerWriteContext.

      SerializeWithXsiTypeAtTopLevel(DataContract dataContract, 

      XmlWriterDelegator xmlWriter, Object obj, 

      RuntimeTypeHandle originalDeclaredTypeHandle, Type graphType) 在 

      System.Runtime.Serialization.DataContractSerializer.

      InternalWriteObjectContent(XmlWriterDelegator writer, Object graph, 

      DataContractResolver dataContractResolver) 在 

      System.Runtime.Serialization.DataContractSerializer.

      InternalWriteObject(XmlWriterDelegator writer, Object graph, 

      DataContractResolver dataContractResolver) 在 

      System.Runtime.Serialization.XmlObjectSerializer.

      WriteObjectHandleExceptions(XmlWriterDelegator writer, Object graph, 

      DataContractResolver dataContractResolver) 在 

      System.Runtime.Serialization.DataContractSerializer.WriteObject

      (XmlWriter writer, Object graph) 在 

      System.Net.Http.Formatting.XmlMediaTypeFormatter.<>c__DisplayClass7.

      <WriteToStreamAsync>b__6() 在

      System.Threading.Tasks.TaskHelpers.RunSynchronously(Action action, 

      CancellationToken token)

    </StackTrace>

  </InnerException>

</Error>

现在总的情况就是这样了。

这是我第一次用VS2012，第一次用EF，第一次用Database-First，出了问题之后，网上找了很多很多，可是实在不知道怎么办了，故来求助各位大虾，到底是什么问题？项目已经完全停滞了

还望高人能略指点迷津！真心地感谢呐~~~~~

Entity Framework Database First C# ASP.NET XML --------------------编程问答-------------------- 请各位大虾赐教，lz在线等啊 --------------------编程问答-------------------- 解决.Net MVC EntityFramework Json 序列化循环引用问题.

解决.Net MVC EntityFramework Json 序列化循环引用问题. --------------------编程问答--------------------

引用 2 楼 geass 的回复:

解决.Net MVC EntityFramework Json 序列化循环引用问题.

解决.Net MVC EntityFramework Json 序列化循环引用问题.

嗯，先谢过，我马上去看看~

补充：.NET技术 ,  ASP.NET