There is an error with linq “System.NotSupportedEx

Question

Could you help to solve the problem with this error or say how it can be done differently. Thank you!

My task is to output the result (collection) with a note for each entity in it. If the user has it in the elected.

protected Expression < Func < TEntity, TBindingModel > > MapToBindingModel;  
protected ApplicationUserManager UserManager => Request.GetOwinContext().GetUserManager<ApplicationUserManager>();


internal ApplicationUser _applicationUser;

[HttpGet]
[Route]
[EnableQuery]
public virtual async Task<IHttpActionResult> GetAll()
{
    _applicationUser = await UserManager.FindByIdAsync(User.Identity.GetUserId());
    if (_applicationUser == null)
        return BadRequest("User is not found");

    return Ok(Service.GetAll().Select(MapToBindingModel));
}

MapToBindingModel = title => new TitleBindingModel
    {
        Id = title.Id,
       //data..
        Favorite = _applicationUser != null && _applicationUser.Favorite.Titles.Any(i=>i.Id == title.Id)       
    };       

Here is the error message:

{
    "Message": "An error has occurred.",
    "ExceptionMessage": "Could not create constant with type \"Domain.Authorization.ApplicationUser\". In this context only primitive types and enumeration types are supported.",
    "ExceptionType": "System.NotSupportedException",
    "StackTrace": "   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.ConstantTranslator.TypedTranslate(ExpressionConverter parent, ConstantExpression linq)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.EqualsTranslator.CreateIsNullExpression(ExpressionConverter parent, Expression input)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.NotTranslator.TypedTranslate(ExpressionConverter parent, UnaryExpression linq)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.BinaryTranslator.TypedTranslate(ExpressionConverter parent, BinaryExpression linq)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MemberInitTranslator.TypedTranslate(ExpressionConverter parent, MemberInitExpression linq)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SelectTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.Convert()\r\n   в System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption)\r\n   в System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass7.<GetResults>b__6()\r\n   в System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)\r\n   в System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass7.<GetResults>b__5()\r\n   в System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)\r\n   в System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)\r\n   в System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0()\r\n   в System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()\r\n   в Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList(JsonWriter writer, IEnumerable values, JsonArrayContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n   в Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType)\r\n   в Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value, Type objectType)\r\n   в System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n   в System.Net.Http.Formatting.JsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n   в System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStreamAsync(Type type, Object value, Stream writeStream, HttpContent content, TransportContext transportContext, CancellationToken cancellationToken)\r\n--- Конец трассировка стека из предыдущего расположения, где возникло исключение ---\r\n   в System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n   в System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   в System.Web.Http.Owin.HttpMessageHandlerAdapter.<BufferResponseContentAsync>d__27.MoveNext()"
}

Answer 1

You need a ToList() before .Select(MapToBindingModel)

Since EF can't project your results to TitleBindingModel you should materialize the result of GetAll() before attempting to map them.

public virtual async Task<IHttpActionResult> GetAll()
{
    ...

    return Ok(Service.GetAll().ToList().Select(MapToBindingModel));
}