blocks|key|159844|text|当涉及到从Web+Api+(或任何其他web服务)向使用者返回数据时，我强烈建议不要传递来自数据库的实体。使用模型更可靠、更易于维护，在模型中您可以控制数据的外观，而不是数据库。这样，您就不必在WebApiConfig中花费太多时间处理格式化程序。您可以只创建一个将子模型作为属性的UserModel，并去掉返回对象中的引用循环。这使得序列化程序更加令人满意。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|159845|此外，如果您只是在请求中指定“Accept”标头，则没有必要删除格式化程序或支持的媒体类型。玩弄这些东西有时会让事情变得更加混乱。|159846|示例：|159847|public+class+UserModel+{
++++public+string+Name+{get;set;}
++++public+string+Age+{get;set;}
++++//+Other+properties+here+that+do+not+reference+another+UserModel+class.
}|code-block|syntax|javascript|159848|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|O|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|P|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

When it comes to returning data back to the consumer from Web Api (or any other web service for that matter), I highly recommend not passing back entities that come from a database. It is much more reliable and maintainable to use Models in which you have control of what the data looks like and not the database. That way you don't have to mess around with the formatters so much in the WebApiConfig. You can just create a UserModel that has child Models as properties and get rid of the reference loops in the return objects. That makes the serializer much happier.

Also, it isn't necessary to remove formatters or supported media types typically if you are just specifying the "Accepts" header in the request. Playing around with that stuff can sometimes make things more confusing.

Example:

<pre><code>public class UserModel {
 public string Name {get;set;}
 public string Age {get;set;}
 // Other properties here that do not reference another UserModel class.
}
</code></pre>

blocks|key|2746578|text|也有这种情况会生成相同的错误：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2746579|如果返回的是List<dynamic>+to+web+api方法|offset|length|style|CODE|2746580|示例：|2746581|public+HttpResponseMessage+Get()
{
++++var+item+=+new+List<dynamic>+{+new+TestClass+{+Name+=+"Ale",+Age+=+30+}+};

++++return+Request.CreateResponse(HttpStatusCode.OK,+item);
}

public+class+TestClass
{
++++public+string+Name+{+get;+set;+}
++++public+int+Age+{+get;+set;+}
}|code-block|syntax|javascript|2746582|因此，对于此场景，在返回类中使用KnownTypeAttribute+(全部)，如下所示：|2746583|[KnownTypeAttribute(typeof(TestClass))]
public+class+TestClass
{
++++public+string+Name+{+get;+set;+}
++++public+int+Age+{+get;+set;+}
}|2746584|这对我来说很有效！|2746585|entityMap^0|0|6|D|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@$D|Y|E|Z|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|10|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|11|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|12|8|@]|9|@]|A|$]]|$1|Q|3|R|5|L|7|13|8|@]|9|@]|A|$M|N]]|$1|S|3|T|5|6|7|14|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

There's also this scenario that generate same error:

In case of the return being a <code>List&lt;dynamic&gt;</code> to web api method

Example:

<pre><code>public HttpResponseMessage Get()
{
 var item = new List&lt;dynamic&gt; { new TestClass { Name = "Ale", Age = 30 } };

 return Request.CreateResponse(HttpStatusCode.OK, item);
}

public class TestClass
{
 public string Name { get; set; }
 public int Age { get; set; }
}
</code></pre>

So, for this scenario use the [KnownTypeAttribute] in the return class (all of them) like this:

<pre><code>[KnownTypeAttribute(typeof(TestClass))]
public class TestClass
{
 public string Name { get; set; }
 public int Age { get; set; }
}
</code></pre>

This works for me!

blocks|key|156178|text|如果您正在使用EF，除了在Global.asax上添加以下代码|type|unstyled|depth|inlineStyleRanges|entityRanges|data|156179|GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings
++++.ReferenceLoopHandling+=+Newtonsoft.Json.ReferenceLoopHandling.Ignore;
GlobalConfiguration.Configuration.Formatters
++++.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);++++++++++|code-block|syntax|javascript|156180|别忘了导入|156181|using+System.Data.Entity;|156182|然后你可以返回你自己的EF模型|156183|就这么简单！|156184|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

If you are working with EF, besides adding the code below on Global.asax

<pre><code>GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings
 .ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
GlobalConfiguration.Configuration.Formatters
 .Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter); 
</code></pre>

Dont`t forget to import 

<pre><code>using System.Data.Entity;
</code></pre>

Then you can return your own EF Models

Simple as that!

blocks|key|2959259|text|我不喜欢这个代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2959260|foreach(var+user+in+db.Users)|offset|length|style|CODE|2959261|作为另一种选择，人们可能会这样做，这对我很有效：|2959262|var+listOfUsers+=+db.Users.Select(r+=>+new+UserModel
+++++++++++++++++++++++++{
+++++++++++++++++++++++++++++userModel.FirstName+=+r.FirstName;
+++++++++++++++++++++++++++++userModel.LastName+=+r.LastName;

+++++++++++++++++++++++++});

return+listOfUsers.ToList();|code-block|syntax|javascript|2959263|然而，我最终还是使用了Lucas+Roselli的解决方案。|2959264|更新:通过返回匿名对象进行简化：|BOLD|2959265|var+listOfUsers+=+db.Users.Select(r+=>+new+
+++++++++++++++++++++++++{
+++++++++++++++++++++++++++++FirstName+=+r.FirstName;
+++++++++++++++++++++++++++++LastName+=+r.LastName;
+++++++++++++++++++++++++});

return+listOfUsers.ToList();|2959266|entityMap^0|0|0|T|0|0|0|0|0|G|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Y|8|@$D|Z|E|10|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|11|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|12|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|13|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|14|8|@$D|15|E|16|F|S]]|9|@]|A|$]]|$1|T|3|U|5|L|7|17|8|@]|9|@]|A|$M|N]]|$1|V|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|W|$]]

I don't like this code: 

<code>foreach(var user in db.Users)
</code>

As an alternative, one might do something like this, which worked for me:

<pre><code>var listOfUsers = db.Users.Select(r =&gt; new UserModel
 {
 userModel.FirstName = r.FirstName;
 userModel.LastName = r.LastName;

 });

return listOfUsers.ToList();
</code></pre>

However, I ended up using Lucas Roselli's solution.

Update: Simplified by returning an anonymous object:

<pre><code>var listOfUsers = db.Users.Select(r =&gt; new 
 {
 FirstName = r.FirstName;
 LastName = r.LastName;
 });

return listOfUsers.ToList();
</code></pre>

blocks|key|158601|text|补充jensendp的答案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|158602|我会将实体传递给用户创建的模型，并使用该实体中的值来设置新创建的模型中的值。例如：|158603|public+class+UserInformation+{
+++public+string+Name+{+get;+set;+}
+++public+int+Age+{+get;+set;+}

+++public+UserInformation(UserEntity+user)+{
++++++this.Name+=+user.name;
++++++this.Age+=+user.age;
+++}
}|code-block|syntax|javascript|158604|然后将返回类型更改为：IEnumerable<UserInformation>|offset|length|style|CODE|158605|entityMap^0|0|0|0|B|S|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|T|8|@$K|U|L|V|M|N]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

To add to jensendp's answer:

I would pass the entity to a user created model and use the values from that entity to set the values in your newly created model. For example:

<pre><code>public class UserInformation {
 public string Name { get; set; }
 public int Age { get; set; }

 public UserInformation(UserEntity user) {
 this.Name = user.name;
 this.Age = user.age;
 }
}
</code></pre>

Then change your return type to: <code>IEnumerable&lt;UserInformation&gt;</code>

blocks|key|2746733|text|给出正确的答案是一种方法，然而，当你可以通过一个配置设置来修复它时，这是一种过度杀伤力。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|2746734|最好在dbcontext构造函数中使用它|2746735|public+DbContext()+//+dbcontext+constructor
++++++++++++:+base("name=ConnectionStringNameFromWebConfig")
{
+++++this.Configuration.LazyLoadingEnabled+=+false;
+++++this.Configuration.ProxyCreationEnabled+=+false;
}|code-block|syntax|javascript|2746736|Asp.Net+Web+API+Error:+The+'ObjectContent`1'+type+failed+to+serialize+the+response+body+for+content+type+'application/xml;+charset=utf-8'|2746737|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/13959048/asp-net-web-api-error-the-objectcontent1-type-failed-to-serialize-the-respon^0|0|18|0|0|0|0|3T|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|10|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|11|8|@]|D|@$9|12|A|13|1|14]]|E|$]]|$1|O|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

Given right answer is one way to go, however it is an overkill when you can fix it by one config settings.

Better to use it in the dbcontext constructor 

<pre><code>public DbContext() // dbcontext constructor
 : base("name=ConnectionStringNameFromWebConfig")
{
 this.Configuration.LazyLoadingEnabled = false;
 this.Configuration.ProxyCreationEnabled = false;
}
</code></pre>

<a href="https://stackoverflow.com/questions/13959048/asp-net-web-api-error-the-objectcontent1-type-failed-to-serialize-the-respon">Asp.Net Web API Error: The &#39;ObjectContent`1&#39; type failed to serialize the response body for content type &#39;application/xml; charset=utf-8&#39;</a>

blocks|key|2959390|text|使用AutoMapper...|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2959391|public+IEnumerable<User>+GetAll()
++++{
++++++++using+(Database+db+=+new+Database())
++++++++{
++++++++++++var+users+=+AutoMapper.Mapper.DynamicMap<List<User>>(db.Users);
++++++++++++return+users;
++++++++}
++++}|code-block|syntax|javascript|2959392|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Use AutoMapper...

<pre><code>public IEnumerable&lt;User&gt; GetAll()
 {
 using (Database db = new Database())
 {
 var users = AutoMapper.Mapper.DynamicMap&lt;List&lt;User&gt;&gt;(db.Users);
 return users;
 }
 }
</code></pre>

blocks|key|2959400|text|我收到此错误的另一种情况是，当我的数据库查询返回空值，但我的用户/视图模型类型被设置为不可为空时。例如，将my+UserModel字段从int更改为int?+resolved。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2959401|entityMap^0|1W|3|22|4|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

Another case where I received this error was when my database query returned a null value but my user/view model type was set as non-nullable. For example, changing my UserModel field from <code>int</code> to <code>int?</code> resolved.

blocks|key|2959423|text|在Application_Start上将此代码添加到下面的global.asax|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2959424|从.Ignore更新到.Serialize。它必须起作用。|2959425|GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling+=+Newtonsoft.Json.ReferenceLoopHandling.Serialize;
++++++++++++GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);|code-block|syntax|javascript|2959426|entityMap^0|1|H|T|B|0|1|7|B|A|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|Y|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|N|$]]

Add this code to <code>global.asax</code> below on <code>Application_Start</code>:

Update from <code>.Ignore</code> to <code>.Serialize</code> . It must work.

<pre><code>GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Serialize;
 GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);
</code></pre>

blocks|key|2959431|text|我个人最喜欢的是:只需将下面的代码添加到App_Start/WebApiConfig.cs。默认情况下，这将返回json而不是XML，还可以防止出现类似的错误。不需要编辑Global.asax来删除XmlFormatter等。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2959432|2959433|+'ObjectContent`1‘类型无法序列化内容类型'application/xml；字符集=utf-8的响应正文|blockquote|2959434|2959435|2959436|config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new+MediaTypeHeaderValue("text/html"));|code-block|syntax|javascript|2959437|entityMap^0|K|P|2D|B|2R|C|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]|$1|G|3|H|5|I|7|10|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|11|8|@]|D|@]|E|$]]|$1|K|3|-4|5|6|7|12|8|@]|D|@]|E|$]]|$1|L|3|M|5|N|7|13|8|@]|D|@]|E|$O|P]]|$1|Q|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|R|$]]

My personal favorite: Just add the code below to <code>App_Start/WebApiConfig.cs</code>. This will return json instead of XML by default and also prevent the error you had. No need to edit <code>Global.asax</code> to remove <code>XmlFormatter</code> etc.

<blockquote>
 The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8
</blockquote>

<pre><code>config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));
</code></pre>

blocks|key|2959439|text|public+class+UserController+:+ApiController
{

+++Database+db+=+new+Database();

+++//+construction
+++public+UserController()
+++{
++++++//+Add+the+following+code
++++++//+problem+will+be+solved
++++++db.Configuration.ProxyCreationEnabled+=+false;
+++}

+++public+IEnumerable<User>+GetAll()
++++{
++++++++++++return+db.Users.ToList();
++++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2959440|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>public class UserController : ApiController
{

 Database db = new Database();

 // construction
 public UserController()
 {
 // Add the following code
 // problem will be solved
 db.Configuration.ProxyCreationEnabled = false;
 }

 public IEnumerable&lt;User&gt; GetAll()
 {
 return db.Users.ToList();
 }
}
</code></pre>

blocks|key|2959447|text|使用以下命名空间：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2959448|using+System.Web.OData;|offset|length|style|CODE|2959449|而不是：|2959450|using+System.Web.Http.OData;|2959451|这对我很管用|2959452|entityMap^0|0|0|N|0|0|0|S|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@$D|R|E|S|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|T|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|U|8|@$D|V|E|W|F|G]]|9|@]|A|$]]|$1|L|3|M|5|6|7|X|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|O|$]]

Use the following namespace:

<code>using System.Web.OData;</code>

Instead of :

<code>using System.Web.Http.OData;</code>

It worked for me

blocks|key|2959463|text|对我有效的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2959464|2959465|对要序列化的类使用[DataContract]，对每个属性使用[DataMember]属性。这足以获得Json结果(例如。|ordered-list-item|offset|length|style|CODE|2959466|要在Global.asax中获得xml序列化，请编写以下代码：|2959467|2959468|var+xml+=+GlobalConfiguration.Configuration.Formatters.XmlFormatter;+xml.UseXmlSerializer+=+true;|2959469|Read这篇文章，它帮助我理解了序列化：https://www.asp.net/web-api/overview/formats-and-model-binding/json-and-xml-serialization|unordered-list-item|2959470|2959471|entityMap|0|LINK|mutability|MUTABLE|url|https://www.asp.net/web-api/overview/formats-and-model-binding/json-and-xml-serialization^0|0|0|9|E|V|C|0|2|B|0|0|0|2P|0|K|2H|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|11|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|12|8|@$F|13|G|14|H|I]|$F|15|G|16|H|I]]|9|@]|A|$]]|$1|J|3|K|5|E|7|17|8|@$F|18|G|19|H|I]]|9|@]|A|$]]|$1|L|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|1B|8|@$F|1C|G|1D|H|I]]|9|@]|A|$]]|$1|O|3|P|5|Q|7|1E|8|@]|9|@$F|1F|G|1G|1|1H]]|A|$]]|$1|R|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|1J|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

Solution that worked for me:

<ol>
<li>Use <code>[DataContract]</code> for class and <code>[DataMember]</code> attributes for each property to serialize. This is enough to get Json result (for ex. from fiddler).</li>
<li>To get xml serialization write in <code>Global.asax</code> this code:

<code>var xml = GlobalConfiguration.Configuration.Formatters.XmlFormatter;
xml.UseXmlSerializer = true;</code></li>
<li>Read this article, it helped me to understand serialization:
<a href="https://www.asp.net/web-api/overview/formats-and-model-binding/json-and-xml-serialization" rel="nofollow noreferrer">https://www.asp.net/web-api/overview/formats-and-model-binding/json-and-xml-serialization</a></li>
</ol>

blocks|key|2959484|text|当Response-Type不是public时，也会发生这种情况！当我使用Visual+Studio生成类型时，我返回了一个内部类。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2959485|internal+class+-->+public+class|code-block|syntax|javascript|2959486|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This also happens when the Response-Type is not public!
I returned an internal class as I used Visual Studio to generate me the type.

<pre><code>internal class --&gt; public class
</code></pre>

blocks|key|156324|text|虽然上面所有这些答案都是正确的，但您可能需要检查InnerException+>+ExceptionMessage。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|156325|如果它像这样说“T+connection.”，则说明ObjectContext实例已被释放，不能再用于需要Connection.的操作。由于EF的默认行为，这可能是一个问题。|156326|通过在DbContext构造函数中指定LazyLoadingEnabled+=false，就可以做到这一点。|156327|public+class+MyDbContext+:+DbContext
{
++public+MyDbContext()
++{
++++this.Configuration.LazyLoadingEnabled+=+false;
++}
}|code-block|syntax|javascript|156328|有关EF的EagerLoading和LazyLoading行为的更多详细信息，请参阅此MSDN+Article。|156329|entityMap|0|LINK|mutability|MUTABLE|url|https://msdn.microsoft.com/en-us/data/jj574232.aspx^0|O|X|0|0|J|Q|0|0|17|C|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|11|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|J|3|K|5|L|7|15|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|16|8|@]|D|@$9|17|A|18|1|19]]|E|$]]|$1|Q|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]]]

While all these answers above are correct, one may want to check the InnerException > ExceptionMessage. 

If it says something like this "The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.". This could be an issue because of default behavior of the EF. 

By assigning LazyLoadingEnabled = false in your DbContext constructor will do the trick.

<pre><code>public class MyDbContext : DbContext
{
 public MyDbContext()
 {
 this.Configuration.LazyLoadingEnabled = false;
 }
}
</code></pre>

For more detailed reading about EagerLoading and LazyLoading behavior of EF refer this <a href="https://msdn.microsoft.com/en-us/data/jj574232.aspx" rel="nofollow noreferrer">MSDN Article</a>.

blocks|key|2959556|text|将此代码添加到Global.asax文件的Application_Start()方法中应该可以解决这个问题|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2959557|protected+void+Application_Start()
{
++++GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings
++++++++.ReferenceLoopHandling+=+Newtonsoft.Json.ReferenceLoopHandling.Ignore;
++++GlobalConfiguration.Configuration.Formatters
++++++++.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);+
//+...
}|code-block|syntax|javascript|2959558|方法2:不推荐|2959559|如果您正在使用EntityFramework，则可以在DbContext类构造函数中禁用代理。注意:如果更新模型，此代码将被删除|2959560|public+class+MyDbContext+:+DbContext
{
++public+MyDbContext()
++{
++++this.Configuration.ProxyCreationEnabled+=+false;
++}
}|2959561|entityMap^0|7|B|L|J|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|Z|8|@]|D|@]|E|$]]|$1|O|3|P|5|H|7|10|8|@]|D|@]|E|$I|J]]|$1|Q|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|R|$]]

Adding this in your <code>Application_Start()</code> method of <code>Global.asax</code> file should solve the problem

<pre><code>protected void Application_Start()
{
 GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings
 .ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
 GlobalConfiguration.Configuration.Formatters
 .Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter); 
// ...
}
</code></pre>

METHOD 2: [Not recommended] 
If you are working with EntityFramework, you can disable proxy in your DbContext class constructor. NOTE: this code wll be removed if you update the model

<pre><code>public class MyDbContext : DbContext
{
 public MyDbContext()
 {
 this.Configuration.ProxyCreationEnabled = false;
 }
}
</code></pre>

blocks|key|2959645|text|在我的例子中，我收到了类似的错误消息：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2959646|2959647|+'ObjectContent`1‘类型无法序列化内容类型'application/xml；charset=utf-8’的响应正文。|blockquote|2959648|2959649|2959650|但是当我深入研究它的时候，问题是：|2959651|数据协定名称为'SomeSubRootType://schemas.datacontract.org/2004/07/WhatEverService‘的|2959652|类型“name.SomeSubRootType”不应为空。如果您正在使用DataContractResolver，请考虑使用DataContractSerializer，或者将任何未知类型静态添加到已知类型列表中-例如，通过使用KnownTypeAttribute属性或通过将它们添加到传递给序列化程序的已知类型列表中。|2959653|2959654|2959655|我通过添加KnownType解决了这个问题。|offset|length|style|CODE|2959656|[KnownType(typeof(SomeSubRootType))]
public+partial+class+SomeRootStructureType|code-block|syntax|javascript|2959657|这个问题的解决灵感来自于这个answer。|2959658|参考：https://msdn.microsoft.com/en-us/library/ms730167(v=vs.100).aspx|2959659|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/8794594/type-not-expected-using-datacontractserializer-but-its-just-a-simple-class|1|https://msdn.microsoft.com/en-us/library/ms730167(v=vs.100).aspx^0|0|0|0|0|0|0|0|0|0|0|5|9|0|0|E|6|0|0|3|1S|1|0^^$0|@$1|2|3|4|5|6|7|1E|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|1G|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]|$1|G|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|1J|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|1K|8|@]|9|@]|A|$]]|$1|L|3|M|5|E|7|1L|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|1M|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|1N|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|1O|8|@$R|1P|S|1Q|T|U]]|9|@]|A|$]]|$1|V|3|W|5|X|7|1R|8|@]|9|@]|A|$Y|Z]]|$1|10|3|11|5|6|7|1S|8|@]|9|@$R|1T|S|1U|1|1V]]|A|$]]|$1|12|3|13|5|6|7|1W|8|@]|9|@$R|1X|S|1Y|1|1Z]]|A|$]]|$1|14|3|-4|5|6|7|20|8|@]|9|@]|A|$]]]|15|$16|$5|17|18|19|A|$1A|1B]]|1C|$5|17|18|19|A|$1A|1D]]]]

In my case I have had similar error message:

<blockquote>
 The 'ObjectContent`1' type failed to serialize the response body for
 content type 'application/xml; charset=utf-8'.
</blockquote>

But when I dig deeper in it, the issue was:

<blockquote>
 Type 'name.SomeSubRootType'
 with data contract name
 'SomeSubRootType://schemas.datacontract.org/2004/07/WhatEverService'
 is not expected. Consider using a DataContractResolver if you are
 using DataContractSerializer or add any types not known statically to
 the list of known types - for example, by using the KnownTypeAttribute
 attribute or by adding them to the list of known types passed to the
 serializer.
</blockquote>

The way I solved by adding <code>KnownType</code>.

<pre><code>[KnownType(typeof(SomeSubRootType))]
public partial class SomeRootStructureType
</code></pre>

This was solved inspired from this <a href="https://stackoverflow.com/questions/8794594/type-not-expected-using-datacontractserializer-but-its-just-a-simple-class">answer</a>.

Reference: <a href="https://msdn.microsoft.com/en-us/library/ms730167(v=vs.100).aspx" rel="nofollow noreferrer">https://msdn.microsoft.com/en-us/library/ms730167(v=vs.100).aspx</a>

blocks|key|158813|text|我使用此代码将其解析为WebApiConfig.cs文件|type|unstyled|depth|inlineStyleRanges|entityRanges|data|158814|var+json+=+config.Formatters.JsonFormatter;
json.SerializerSettings.PreserveReferencesHandling+=+Newtonsoft.Json.PreserveReferencesHandling.Objects;+
config.Formatters.Remove(config.Formatters.XmlFormatter);|code-block|syntax|javascript|158815|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I resolved it using this code to WebApiConfig.cs file

<pre><code>var json = config.Formatters.JsonFormatter;
json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects; 
config.Formatters.Remove(config.Formatters.XmlFormatter);
</code></pre>

blocks|key|158854|text|​|type|unstyled|depth|inlineStyleRanges|entityRanges|data|158855|📷|atomic|offset|length|158856|158857|我基本上添加了一行，它们是|158858|158859|entities.Configuration.ProxyCreationEnabled+=+false;|unordered-list-item|158860|158861|转到UsersController.cs|158862|using+System;
using+System.Collections.Generic;
using+System.Linq;
using+System.Net;
using+System.Net.Http;
using+System.Web.Http;
using+UserDataAccess;

namespace+SBPMS.Controllers
{
++++public+class+UsersController+:+ApiController
++++{


++++++++public+IEnumerable<User>+Get()+{
++++++++++++using+(SBPMSystemEntities+entities+=+new+SBPMSystemEntities())+{
++++++++++++++++entities.Configuration.ProxyCreationEnabled+=+false;
++++++++++++++++return+entities.Users.ToList();
++++++++++++}
++++++++}
++++++++public+User+Get(int+id)+{
++++++++++++using+(SBPMSystemEntities+entities+=+new+SBPMSystemEntities())+{
++++++++++++++++entities.Configuration.ProxyCreationEnabled+=+false;
++++++++++++++++return+entities.Users.FirstOrDefault(e+=>+e.user_ID+==+id);
++++++++++++}
++++++++}
++++}
}|code-block|syntax|javascript|158863|158864|158865|158866|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/f39c9967e3f182cb22f31eea4b068882.png|imageAlt|1|https://ask.qcloudimg.com/http-save/yehe-900000/3f64c8b183eba64a2801cf62b93b55fd.png^0|0|0|1|0|0|0|0|0|0|0|0|0|0|0|1|1|0|0^^$0|@$1|2|3|4|5|6|7|19|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1A|8|@]|9|@$E|1B|F|1C|1|1D]]|A|$]]|$1|G|3|4|5|6|7|1E|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|1F|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]|$1|K|3|L|5|M|7|1H|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|1J|8|@]|9|@]|A|$]]|$1|Q|3|R|5|S|7|1K|8|@]|9|@]|A|$T|U]]|$1|V|3|4|5|6|7|1L|8|@]|9|@]|A|$]]|$1|W|3|C|5|D|7|1M|8|@]|9|@$E|1N|F|1O|1|1P]]|A|$]]|$1|X|3|4|5|6|7|1Q|8|@]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1R|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15|16|-4]]|17|$5|11|12|13|A|$14|18|16|-4]]]]

<a href="https://i.stack.imgur.com/nUeDQ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nUeDQ.png" alt="This is my error"></a>

I basically add one line which they are 

<ul>
<li>entities.Configuration.ProxyCreationEnabled = false;</li>
</ul>

to UsersController.cs 

<pre><code>using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using UserDataAccess;

namespace SBPMS.Controllers
{
 public class UsersController : ApiController
 {


 public IEnumerable&lt;User&gt; Get() {
 using (SBPMSystemEntities entities = new SBPMSystemEntities()) {
 entities.Configuration.ProxyCreationEnabled = false;
 return entities.Users.ToList();
 }
 }
 public User Get(int id) {
 using (SBPMSystemEntities entities = new SBPMSystemEntities()) {
 entities.Configuration.ProxyCreationEnabled = false;
 return entities.Users.FirstOrDefault(e =&gt; e.user_ID == id);
 }
 }
 }
}
</code></pre>

<a href="https://i.stack.imgur.com/56TKm.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/56TKm.png" alt="Here is my output:"></a>

blocks|key|156436|text|Visual+Studio+2017或2019在这方面完全没有考虑到这一点，因为Visual+Studio本身要求输出是json格式，而Visual+Studio的默认格式是"XmlFormat“json|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|156437|Visual+Studio应该自动完成此操作，而不是给开发人员带来如此多的麻烦。|156438|要纠正此问题，请转到WebApiConfig.cs文件，然后添加|156439|json.SerializerSettings.PreserveReferencesHandling+=+Newtonsoft.Json.PreserveReferencesHandling.Objects；config.Formatters.Remove(config.Formatters.XmlFormatter);；var+json+=config.Formatters.JsonFormatter|156440|在寄存器(HttpConfiguration配置)方法中的"config.MapHttpAttributeRoutes();“之后。这将允许您的项目生成json输出。|156441|entityMap^0|1O|4|2G|E|0|0|14|0|0|W|0|0|4H|4I|15|0|0|2B|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]|$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|J|3|K|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|L|3|M|5|6|7|15|8|@$9|16|A|17|B|C]]|D|@]|E|$]]|$1|N|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|O|$]]

Visual Studio 2017 or 2019 is totally unthoughtful on this, because Visual Studio itself requires the output to be in json format, while Visual Studio's default format is "XmlFormat" (config.Formatters.XmlFormatter).

Visual Studio should do this automatically instead of giving developers so much trouble.

To correct this problem, go to the WebApiConfig.cs file, and add

var json = config.Formatters.JsonFormatter;
 json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects;
 config.Formatters.Remove(config.Formatters.XmlFormatter); 

after "config.MapHttpAttributeRoutes();" in the Register(HttpConfiguration config) method. This would allow your project to produce json output.

blocks|key|158884|text|在我的例子中，我解决了重新创建数据库的问题。我在一个模型中做了一些更改，并在Package+Manager控制台中启动Update-Database，我得到了以下错误：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|158885|158886|“ALTER+TABLE语句与外键约束"FK_dbo.Activities_dbo.Projects_ProjectId”冲突。冲突发生在数据库"TrackEmAllContext-20190530144302“、表"dbo.Projects”、列“Id”中。“|blockquote|158887|158888|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|J|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|K|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|L|8|@]|9|@]|A|$]]|$1|G|3|-4|5|6|7|M|8|@]|9|@]|A|$]]]|H|$]]

In my case I solved recreating the database.
I made some changes in a model and launching Update-Database in Package Manager Console I got the following Error: 

<blockquote>
 "The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_dbo.Activities_dbo.Projects_ProjectId". The conflict occurred in database "TrackEmAllContext-20190530144302", table "dbo.Projects", column 'Id'."
</blockquote>

blocks|key|156521|text|以防:如果向WebApiConfig.cs或Global.asax.cs添加代码对您不起作用：|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|156522|.ToList();|code-block|syntax|javascript|156523|添加.ToList()函数。|156524|我尝试了每种解决方案，但下面的方法对我有效：|156525|var+allShops+=+context.shops.Where(s+=>+s.city_id+==+id)**.ToList()**;
return+allShops;|156526|我希望这会有帮助。|156527|entityMap^0|6|F|M|E|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|11|8|@]|D|@]|E|$]]|$1|O|3|P|5|H|7|12|8|@]|D|@]|E|$I|J]]|$1|Q|3|R|5|6|7|13|8|@]|D|@]|E|$]]|$1|S|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|T|$]]

In case: If adding code to WebApiConfig.cs or Global.asax.cs doesn't work for you:

<pre><code>.ToList();
</code></pre>

Add .ToList() function.

I tried out every solution but following worked for me:

<pre><code>var allShops = context.shops.Where(s =&gt; s.city_id == id)**.ToList()**;
return allShops;
</code></pre>

I hope, it helps.

blocks|key|160255|text|添加以下行|type|unstyled|depth|inlineStyleRanges|entityRanges|data|160256|this.Configuration.ProxyCreationEnabled+=+false;|code-block|syntax|javascript|160257|作为false使用ProxyCreationEnabled的两种方法。|offset|length|style|CODE|160258|160259|将其添加到DBContext构造函数中|ordered-list-item|160260|160261|公共ProductEntities()：base("name=ProductEntities")+{+this.Configuration.ProxyCreationEnabled+=+false；}|160262|或|BOLD|160263|160264|在Get方法内添加行|160265|160266|公共IEnumerable+Get()+{+using+(ProductEntities+obj+=新ProductEntities(){+this.Configuration.ProxyCreationEnabled+=+false；return+obj.Brand_Details.ToList()；}+}|160267|entityMap^0|0|0|2|5|9|K|0|0|5|9|0|0|0|0|1|0|0|1|3|0|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|15|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|16|8|@$I|17|J|18|K|L]|$I|19|J|1A|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]|$1|N|3|O|5|P|7|1C|8|@$I|1D|J|1E|K|L]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]|$1|R|3|S|5|6|7|1G|8|@]|9|@]|A|$]]|$1|T|3|U|5|6|7|1H|8|@$I|1I|J|1J|K|V]]|9|@]|A|$]]|$1|W|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]|$1|X|3|Y|5|P|7|1L|8|@$I|1M|J|1N|K|L]]|9|@]|A|$]]|$1|Z|3|-4|5|6|7|1O|8|@]|9|@]|A|$]]|$1|10|3|11|5|6|7|1P|8|@]|9|@]|A|$]]|$1|12|3|-4|5|6|7|1Q|8|@]|9|@]|A|$]]]|13|$]]

Add the below line 

<pre><code>this.Configuration.ProxyCreationEnabled = false;
</code></pre>

Two way to use <code>ProxyCreationEnabled</code> as <code>false</code>.

<ol>
<li>Add it inside of <code>DBContext</code> Constructor

<pre><code>public ProductEntities() : base("name=ProductEntities")
{
 this.Configuration.ProxyCreationEnabled = false;
}
</code></pre></li>
</ol>

OR

<ol start="2">
<li>Add the line inside of <code>Get</code> method

<pre><code>public IEnumerable&lt;Brand_Details&gt; Get()
{
 using (ProductEntities obj = new ProductEntities())
 {
 this.Configuration.ProxyCreationEnabled = false;
 return obj.Brand_Details.ToList();
 }
}
</code></pre></li>
</ol>

blocks|key|2959979|text|对类使用Serializable：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2959980|示例：|2959981|[Serializable]
public+class+UserModel+{
++++public+string+Name+{get;set;}
++++public+string+Age+{get;set;}
}|code-block|syntax|javascript|2959982|它对我起作用了！|2959983|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Use [Serializable] for class:

Example:

<pre><code>[Serializable]
public class UserModel {
 public string Name {get;set;}
 public string Age {get;set;}
}
</code></pre>

It worked for me!

blocks|key|160291|text|您必须在App_Start文件夹中的WebApiConfig.cs中定义序列化格式化程序，例如|type|unstyled|depth|inlineStyleRanges|entityRanges|data|160292|添加config.Formatters.Remove(config.Formatters.XmlFormatter)；//，它将为您提供JSON格式的数据。|160293|添加config.Formatters.Remove(config.Formatters.JsonFormatter)；//，它将为您提供XML格式的数据|160294|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

You will have to define Serializer Formatter within WebApiConfig.cs available in App_Start Folder like

Adding config.Formatters.Remove(config.Formatters.XmlFormatter);
 // which will provide you data in JSON Format

Adding config.Formatters.Remove(config.Formatters.JsonFormatter);
 // which will provide you data in XML Format

blocks|key|2960075|text|在我的例子中，当我删除导航属性之前的virtual关键字时，它被修复了，我指的是参考表。所以我改变了|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2960076|public+virtual+MembershipType+MembershipType+{+get;+set;+}|code-block|syntax|javascript|2960077|至：|2960078|public+MembershipType+MembershipType+{+get;+set;+}|2960079|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

in my case, it was fixed when I removed the virtual keyword before my navigation properties,
I mean the reference tables.
so I changed 

<pre><code>public virtual MembershipType MembershipType { get; set; }
</code></pre>

to:

<pre><code>public MembershipType MembershipType { get; set; }
</code></pre>

blocks|key|156577|text|只需在global.asax中添加以下行：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|156578|GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling+=+Newtonsoft.Json.ReferenceLoopHandling.Ignore;++
GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);|code-block|syntax|javascript|156579|导入|156580|using+System.Data.Entity;|156581|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Just put following lines in global.asax:

<pre><code>GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore; 
GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);
</code></pre>

Import

<pre><code>using System.Data.Entity;
</code></pre>

I am working with ASP.NET MVC 5 Web Api. I want consult all my users.

I wrote <code>api/users</code> and I receive this:

<blockquote>
 "The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; charset=utf-8'"
</blockquote>

In WebApiConfig, already I added these lines:

<pre><code>HttpConfiguration config = new HttpConfiguration();
config.Formatters.XmlFormatter.SupportedMediaTypes.Remove(appXmlType);
config.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore; 
</code></pre>

But it still doesn't work.

My function for return data is this:

<pre><code>public IEnumerable&lt;User&gt; GetAll()
{
 using (Database db = new Database())
 {
 return db.Users.ToList();
 }
}
</code></pre>

Failed to serialize the response in Web API with Json

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在使用ASP.NET MVC5WebApi。我想咨询我所有的用户。我写了api/users，我收到了这样的信息：“'ObjectContent`1‘类型无法序列化内容类型'application/json；字符集=utf-8’的响应正文”在WebApiConfig中，我已经添加了以下几行：HttpConfigura...

问无法使用Json在Web API中序列化响应
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