实体框架数据库首先使用Web API

Question

是否可以一起使用Entity Framework，Web API？

申请结构：

1. 使用AngularJS的Web API应用程序
2. 数据访问层：使用实体框架

在我的Web API应用程序中，我想使用DAL中的实体作为模型。

Web API控制器的数据返回应为JSON。

当我尝试它总是会出现这样的错误：

{“$ id”：“1”，“Message”：“发生错误。”，“ExceptionMessage”：“'ObjectContent 1' type failed to serialize the response body for content type 'application/json; charset=utf-8'.","ExceptionType":"System.InvalidOperationException","StackTrace":null,"InnerException":{"$id":"2","Message":"An error has occurred.","ExceptionMessage":"Error while copying content to a stream.","ExceptionType":"System.Net.Http.HttpRequestException","StackTrace":null,"InnerException":{"$id":"3","Message":"An error has occurred.","ExceptionMessage":"The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.","ExceptionType":"System.ObjectDisposedException","StackTrace":" at System.Data.Objects.ObjectContext.EnsureConnection()\r\n at System.Data.Objects.ObjectQuery 1.GetResults（Nullable 1 forMergeOption)\r\n at System.Data.Objects.ObjectQuery 1。 System.Collections.Generic.IEnumerable.GetEnumerator（）\ r \ n at System.Collections.Generic.List 1..ctor(IEnumerable 1 collection）\ r \ n at System.Linq.Enumerable.ToList [TSource]（IEnumerable`1源码）\ r \ n at Newtonsoft.Json.Serialization.JsonArrayContract.CreateWrapper（Object list）\ r \ n在Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue（JsonWriter writer，Object value，JsonContract valueContract，JsonProperty member，JsonContainerContract containerContract， JsonProperty containerProperty）\ r \ n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize（JsonWriter jsonWriter，Object value）\ r \ n在Newtonsoft.Json.JsonSerializer.SerializeInternal（JsonWriter jsonWriter，Object value）\ r \ n在Newtonsoft。 System.Net.Http.Formatting.JsonMediaTypeFormatter中的Json.JsonSerializer.Serialize（JsonWriter jsonWriter，Object value）\ r \ n。＆lt;＆gt; c_ Disp在System.Threading.Tasks.TaskHelpers.RunSynchronously（Action action，CancellationToken令牌）“}}}

中的layClassd.b _c（）\ r \ n

这是我的控制器（当我使用Code First时，相同的代码正常工作）

public class TodoController : ApiController
{
  // GET api/Todo
  public IEnumerable<Todo> GetTodoItems(string q = null, string sort = null, 
       bool desc = false, int? limit = null, int offset = 0)
 {
   using (var db = new AdvanceContext())
   {
     var list = ((IObjectContextAdapter)db).ObjectContext.CreateObjectSet<Todo>();

     IQueryable<Todo> items = string.IsNullOrEmpty(sort)
              ? list.OrderBy(o => o.Priority)
              : list.OrderBy(String.Format("it.{0} {1}", sort, desc ? "DESC" : "ASC"));

     if (!string.IsNullOrEmpty(q) && q != "undefined")
        items = items.Where(t => t.Description.Contains(q));

     if (offset > 0)
        items = items.Skip(offset);

     if (limit.HasValue)
        items = items.Take(limit.Value);

      return items;
  }
 }
}

Answer 1

在您的上下文中添加以下行：

this.Configuration.LazyLoadingEnabled = true;
this.Configuration.ProxyCreationEnabled = false;

示例：

public partial class Dbname : DbContext
{
    public Dbname()
        : base("name=Dbname")
    {
        this.Configuration.LazyLoadingEnabled = true;
        this.Configuration.ProxyCreationEnabled = false;
    }

    public virtual DbSet<dtproperty> dtproperties { get; set; }