在 Azure 移动服务 .NET 中使用 DTO 会引发目标调用异常
Using DTO in Azure Mobile Service .NET throws target invocation exception
我使用 Azure 移动服务 .NET 后端，我们都知道我们必须使用 Entity Framework classes 映射到数据库 creation/migration。
所以我需要使用 DTO 来仅序列化我想要的属性、计算属性等。我正在关注 Field Engineer example。但是Automapper让我很痛苦，尽管我做了所有应该做的事情。
我检查了其他几个博客和网站，有些使用 Automapper，有些则没有，例如 this one。我感觉不使用 Automapper 并使用 Select() 即时创建 DTO 更舒服，就像我之前在实现 Web API.
时所做的那样
我将 TableController class 还原为 Post，使用 EntityDomainManager，并将 GetAllPosts 方法留给了以下方法。
public class PostController : TableController<Post>
{
private MobileServiceContext _context;
protected override void Initialize(HttpControllerContext controllerContext)
{
base.Initialize(controllerContext);
_context = new MobileServiceContext();
DomainManager = new EntityDomainManager<Post>(_context, Request, Services);
}
//[ExpandProperty("User")]
// GET tables/Post
public IQueryable<PostDto> GetAllPost()
{
return Query().Include("User").Select(x => new PostDto());
}
}
我收到以下错误。
{"message":"An error has occurred.","exceptionMessage":"Exception has been thrown by the target of an invocation.","exceptionType":"System.Reflection.TargetInvocationException","stackTrace":" at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)\r\n at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)\r\n at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)\r\n at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)\r\n at System.Web.Http.OData.Query.ODataQueryOptions.LimitResults(IQueryable queryable, Int32 limit, Boolean& resultsLimited)\r\n at System.Web.Http.OData.Query.ODataQueryOptions.ApplyTo(IQueryable query, ODataQuerySettings querySettings)\r\n at System.Web.Http.OData.EnableQueryAttribute.ApplyQuery(IQueryable queryable, ODataQueryOptions queryOptions)\r\n at System.Web.Http.OData.EnableQueryAttribute.ExecuteQuery(Object response, HttpRequestMessage request, HttpActionDescriptor actionDescriptor)\r\n at System.Web.Http.OData.EnableQueryAttribute.OnActionExecuted(HttpActionExecutedContext actionExecutedContext)\r\n at System.Web.Http.Filters.ActionFilterAttribute.OnActionExecutedAsync(HttpActionExecutedContext actionExecutedContext, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.GetResult()\r\n at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Filters.AuthorizationFilterAttribute.<ExecuteAuthorizationFilterAsyncCore>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Controllers.AuthenticationFilterResult.<ExecuteAsync>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()","innerException":{"message":"An error has occurred.","exceptionMessage":"The specified type member 'DatePosted' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.","exceptionType":"System.NotSupportedException","stackTrace":" at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MemberAccessTranslator.TypedTranslate(ExpressionConverter parent, MemberExpression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input, DbExpressionBinding& binding)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateSet(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.ThenByTranslatorBase.Translate(ExpressionConverter parent, MethodCallExpression call)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateSet(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.ThenByTranslatorBase.Translate(ExpressionConverter parent, MethodCallExpression call)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateSet(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.UnarySequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.Convert()\r\n at System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption)\r\n at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass7.<GetResults>b__6()\r\n at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)\r\n at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass7.<GetResults>b__5()\r\n at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)\r\n at System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)\r\n at System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0()\r\n at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()\r\n at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)\r\n at System.Web.Http.OData.Query.TruncatedCollection`1..ctor(IQueryable`1 source, Int32 pageSize)\r\n at System.Web.Http.OData.Query.ODataQueryOptions.LimitResults[T](IQueryable`1 queryable, Int32 limit, Boolean& resultsLimited)"}}
如果我只是将它转换为 Entity Framework class 就可以了。你会注意到我没有填写任何 属性，只是为了测试目的。
我使用 IIS Express 在本地进行测试。
数据对象和模型。
public class Post : EntityData
{
public DateTimeOffset DatePosted { get; set; }
public string StatusText { get; set; }
public PostType TypeOfPost { get; set; }
[ForeignKey("Id")]
public virtual User User { get; set; }
[ForeignKey("Id")]
public virtual ICollection<PostPhotoUrl> PhotoUrls { get; set; }
}
public class PostDto
{
public PostDto()
{
PhotoUrls = new HashSet<PostPhotoUrlDto>();
}
public DateTimeOffset DatePosted { get; set; }
public string StatusText { get; set; }
public int TypeOfPost { get; set; }
public UserDto User { get; set; }
public ICollection<PostPhotoUrlDto> PhotoUrls { get; set; }
}
在网上搜索找不到任何其他更清楚的教程如何使用 Azure 移动服务和 DTO，虽然它不应该引入这样的困难。如果有资源欢迎。
我应该提到，如果我不执行以下操作，测试网站在尝试测试端点时会引发错误。
config.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
异常快照：
我真的不需要这个项目的 DTO，但如果我现在不解决我不明白的问题，它会回来找我的 运行服务。
我不确定，但我认为问题可能出在这行代码上
return Query().Include("User").Select(x => new PostDto());
如果您不使用 AutoMapper，那么您将需要手动解析 Select 语句中的属性，如下所示
return Query().Include("User")
.Select(x => new PostDto()
{
DatePosted = x.DatePosted,
StatusText = x.StatusText,
TypeOfPost = x.TypeOfPost,
User = new UserDto
{
//Your propertoes here
//eg Id = x.User.Id etc
}
);
似乎 Select() LINQ 表达式在元素完全加载或引用仍未设置之前发生冲突。
我将该方法转换为 IEnumerable return 类型并在转换为 DTO 之前急切加载数据。
public IEnumerable<PostDto> GetAllPost()
{
return Query().Include("User").ToList().Select(x => new PostDto
{
DatePosted = x.DatePosted,
StatusText = x.StatusText,
TypeOfPost = (int)x.TypeOfPost,
User = new UserDto
{
Id = x.User.Id
}
});
}
测试我的服务后，它return编辑了我插入数据库中的以下数据。
[
{
"datePosted": "2015-04-27T04:05:38.843Z",
"statusText": "Post Text",
"typeOfPost": 1,
"user": {
"id": "a59d0f12-8bb1-448e-9c08-56f862b77ee4"
},
"photoUrls": []
}
]
现在应该使用 AutoMapper 进行测试，以证明它也适用于它。
唯一未知的是为什么我需要将 ReferenceLoopHandling 属性 设置为 Ignore 以便服务正确显示 JSON 示例数据。
config.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
我使用 Azure 移动服务 .NET 后端，我们都知道我们必须使用 Entity Framework classes 映射到数据库 creation/migration。 所以我需要使用 DTO 来仅序列化我想要的属性、计算属性等。我正在关注 Field Engineer example。但是Automapper让我很痛苦，尽管我做了所有应该做的事情。
我检查了其他几个博客和网站，有些使用 Automapper，有些则没有，例如 this one。我感觉不使用 Automapper 并使用 Select() 即时创建 DTO 更舒服，就像我之前在实现 Web API.
时所做的那样我将 TableController class 还原为 Post，使用 EntityDomainManager，并将 GetAllPosts 方法留给了以下方法。
public class PostController : TableController<Post>
{
private MobileServiceContext _context;
protected override void Initialize(HttpControllerContext controllerContext)
{
base.Initialize(controllerContext);
_context = new MobileServiceContext();
DomainManager = new EntityDomainManager<Post>(_context, Request, Services);
}
//[ExpandProperty("User")]
// GET tables/Post
public IQueryable<PostDto> GetAllPost()
{
return Query().Include("User").Select(x => new PostDto());
}
}
我收到以下错误。
{"message":"An error has occurred.","exceptionMessage":"Exception has been thrown by the target of an invocation.","exceptionType":"System.Reflection.TargetInvocationException","stackTrace":" at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)\r\n at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)\r\n at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)\r\n at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)\r\n at System.Web.Http.OData.Query.ODataQueryOptions.LimitResults(IQueryable queryable, Int32 limit, Boolean& resultsLimited)\r\n at System.Web.Http.OData.Query.ODataQueryOptions.ApplyTo(IQueryable query, ODataQuerySettings querySettings)\r\n at System.Web.Http.OData.EnableQueryAttribute.ApplyQuery(IQueryable queryable, ODataQueryOptions queryOptions)\r\n at System.Web.Http.OData.EnableQueryAttribute.ExecuteQuery(Object response, HttpRequestMessage request, HttpActionDescriptor actionDescriptor)\r\n at System.Web.Http.OData.EnableQueryAttribute.OnActionExecuted(HttpActionExecutedContext actionExecutedContext)\r\n at System.Web.Http.Filters.ActionFilterAttribute.OnActionExecutedAsync(HttpActionExecutedContext actionExecutedContext, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.GetResult()\r\n at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Filters.AuthorizationFilterAttribute.<ExecuteAuthorizationFilterAsyncCore>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Controllers.AuthenticationFilterResult.<ExecuteAsync>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()","innerException":{"message":"An error has occurred.","exceptionMessage":"The specified type member 'DatePosted' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.","exceptionType":"System.NotSupportedException","stackTrace":" at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MemberAccessTranslator.TypedTranslate(ExpressionConverter parent, MemberExpression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input, DbExpressionBinding& binding)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateSet(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.ThenByTranslatorBase.Translate(ExpressionConverter parent, MethodCallExpression call)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateSet(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.ThenByTranslatorBase.Translate(ExpressionConverter parent, MethodCallExpression call)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateSet(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.UnarySequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.Convert()\r\n at System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption)\r\n at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass7.<GetResults>b__6()\r\n at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)\r\n at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass7.<GetResults>b__5()\r\n at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)\r\n at System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)\r\n at System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0()\r\n at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()\r\n at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)\r\n at System.Web.Http.OData.Query.TruncatedCollection`1..ctor(IQueryable`1 source, Int32 pageSize)\r\n at System.Web.Http.OData.Query.ODataQueryOptions.LimitResults[T](IQueryable`1 queryable, Int32 limit, Boolean& resultsLimited)"}}
如果我只是将它转换为 Entity Framework class 就可以了。你会注意到我没有填写任何 属性，只是为了测试目的。
我使用 IIS Express 在本地进行测试。
数据对象和模型。
public class Post : EntityData
{
public DateTimeOffset DatePosted { get; set; }
public string StatusText { get; set; }
public PostType TypeOfPost { get; set; }
[ForeignKey("Id")]
public virtual User User { get; set; }
[ForeignKey("Id")]
public virtual ICollection<PostPhotoUrl> PhotoUrls { get; set; }
}
public class PostDto
{
public PostDto()
{
PhotoUrls = new HashSet<PostPhotoUrlDto>();
}
public DateTimeOffset DatePosted { get; set; }
public string StatusText { get; set; }
public int TypeOfPost { get; set; }
public UserDto User { get; set; }
public ICollection<PostPhotoUrlDto> PhotoUrls { get; set; }
}
在网上搜索找不到任何其他更清楚的教程如何使用 Azure 移动服务和 DTO，虽然它不应该引入这样的困难。如果有资源欢迎。
我应该提到，如果我不执行以下操作，测试网站在尝试测试端点时会引发错误。
config.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
异常快照：
我真的不需要这个项目的 DTO，但如果我现在不解决我不明白的问题，它会回来找我的 运行服务。
我不确定，但我认为问题可能出在这行代码上
return Query().Include("User").Select(x => new PostDto());
如果您不使用 AutoMapper，那么您将需要手动解析 Select 语句中的属性，如下所示
return Query().Include("User")
.Select(x => new PostDto()
{
DatePosted = x.DatePosted,
StatusText = x.StatusText,
TypeOfPost = x.TypeOfPost,
User = new UserDto
{
//Your propertoes here
//eg Id = x.User.Id etc
}
);
似乎 Select() LINQ 表达式在元素完全加载或引用仍未设置之前发生冲突。 我将该方法转换为 IEnumerable return 类型并在转换为 DTO 之前急切加载数据。
public IEnumerable<PostDto> GetAllPost()
{
return Query().Include("User").ToList().Select(x => new PostDto
{
DatePosted = x.DatePosted,
StatusText = x.StatusText,
TypeOfPost = (int)x.TypeOfPost,
User = new UserDto
{
Id = x.User.Id
}
});
}
测试我的服务后，它return编辑了我插入数据库中的以下数据。
[
{
"datePosted": "2015-04-27T04:05:38.843Z",
"statusText": "Post Text",
"typeOfPost": 1,
"user": {
"id": "a59d0f12-8bb1-448e-9c08-56f862b77ee4"
},
"photoUrls": []
}
]
现在应该使用 AutoMapper 进行测试，以证明它也适用于它。
唯一未知的是为什么我需要将 ReferenceLoopHandling 属性 设置为 Ignore 以便服务正确显示 JSON 示例数据。
config.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;