始终有错误“ObjectContent 1类型无法序列化响应正文...” [英] Always have error "The ObjectContent 1 type failed to serialize the response body..."

问题描述

我使用Web api从数据库中检索数据。我只有1个表tblMessage，并希望从该表中获取数据。

I use Web api to retrieve data from the database. I only have 1 table "tblMessage" and want to get data from that table.

我设置了所有的东西，但是当我运行网站。错误总是说

I set everything up but then when I run the website. the error always say

'ObjectContent`1'类型无法序列化内容类型'application / xml

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

我在stackoverflow上读了一些帖子，说出错误可以通过告诉浏览器以json格式输出数据来修复。之后，错误变成

I read some posts on stackoverflow that sayid the error could be fixed by telling the browser to output data in json format. After that, the error becomes

'ObjectContent`1'类型无法将内容类型'application / json

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

我已经尝试过以下帖子中的所有解决方案，但他们不解决问题（浏览器报告相同的错误）

I have tried all solutions from the following posts, but they dont fix the problem ( browser reports the same error)

Web API错误：'ObjectContent`1'类型无法将响应主体序列化为内容类型

无法序列化内容类型的响应正文

Web API错误：'ObjectContent`1'类型无法序列化内容类型的响应正文

这个错误是什么？ / p>

What exactly this error is?

public interface IMessage
{
    IQueryable<Message> GetAll();
}

public class Message
{
    [Key]
    public int i_StmID { get; set; }
    public string vch_MsgString { get; set; } 
}

public class EFDBContext : DbContext
{
    public DbSet<Message> Message { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        modelBuilder.Entity<Message>().ToTable("tblMessage");
    }
}

public class MessageRepository : IMessage
{
    private EFDBContext context = new EFDBContext();

    public IQueryable<Message> GetAll()
    {
        return context.tblMessage;
    }
}

public class MessageController : ApiController
{
    public IMessage repo = new MessageRepository();

    public IEnumerable<Message> GetAllMsg()
    {
        return repo.GetAll();
    }
}

推荐答案

更改 IEnumerable< Message > to 列表< Message>

public IEnumerable<Message> GetAllMsg()
{
    return repo.GetAll();
}

to

public List<Message> GetAllMsg()
{
    return repo.GetAll();
}

更新：
但要注意获取 OutOfMemoryException 因为这个方法会将所有消息对象存储在本地内存中，所以你必须实现某种寻呼。

UPDATE: But beware of getting OutOfMemoryException because this method will store all Message objects in local memory so you have to implement some kind of paging.

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