使用Entity Framework的数据库优先模式与Web API。

Question

使用Entity Framework的数据库优先模式与Web API。

jsonentity-frameworkangularjs

3

可以将Entity Framework和Web API一起使用吗？

应用程序结构：

1.带有AngularJS的Web API应用程序 2.数据访问层：使用Entity Framework

在我的Web API应用程序中，我想要使用DAL中的实体作为模型。

从Web API控制器返回的数据应该是JSON格式。

当我尝试时，总是会出现以下错误：

{"$id":"1","Message":"An error has occurred.","ExceptionMessage":"The '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(Nullable1 forMergeOption)\r\n at System.Data.Objects.ObjectQuery1.System.Collections.Generic.IEnumerable.GetEnumerator()\r\n at System.Collections.Generic.List1..ctor(IEnumerable1 collection)\r\n at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)\r\n at Newtonsoft.Json.Serialization.JsonArrayContract.CreateWrapper(Object list)\r\n at 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 at Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value)\r\n at Newtonsoft.Json.JsonSerializer.Serialize(JsonWriter jsonWriter, Object value)\r\n at System.Net.Http.Formatting.JsonMediaTypeFormatter.<>c_DisplayClassd.b_c()\r\n at System.Threading.Tasks.TaskHelpers.RunSynchronously(Action action, CancellationToken token)"}}

这是我的控制器（当我使用Code First时，相同的代码可以工作）：

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;
  }
 }
}

- Ali Adravi

可以同时使用两者。问题出在你的Web API上。你能添加你想要访问的控制器吗？ - kubuntu

2

您的DataContext正在被释放。将using (var db = new AdvanceContext())更改为： var db = new AdvanceContext(); - Larry Flewwelling

1个回答

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原文链接

- Nimasha Jayathunga · Answer 1

在您的上下文中添加以下行：

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

例子：

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; }