使用Web API生成实体框架搭建API控制器错误。

I have the fowling models:

我有捕鸟模型:

public class Order 
{ 
    public int OrderId { get; set; } 
    //
    public virtual ICollection<Client> Clients { get; set; } 
} 

public class Client 
{ 
    public int ClientId { get; set; } 
    public string ClientName { get; set; } 
    public virtual Order Order { get; set; } 
} 
public c