Get 2 columns of table in a relationship

Question

I have the following Entity Framework 7 entities:

public class EbookFile {    
  public Int32 EbookId { get; set; }
  public Int32 FileId { get; set; }
  public virtual Ebook Ebook { get; set; }
  public virtual File File { get; set; }
}

public class File {
  public Int32 Id { get; set; }
  public Byte[] Content { get; set; }  
  public String Name { get; set; }    
  public virtual ICollection<EbookFile> EbooksFiles { get; set; }
}

Given an EbookId I need to get Ids and Names of all files associated with it:

Dictionary<Int32, Dictionary<String, Int32>> files = await _context
  .EbooksFiles
  .Include(x => x.File)
  .Where(x => result.Select(y => y.Id).Contains(x.EbookId))
  .GroupBy(x => x.EbookId)
  .ToDictionaryAsync(x => x.Key, x => x.ToDictionary(y => y.File.Name, y => y.File.Id));

The problem is that I am also getting the Content which I do not want:

SELECT [x].[EbookId], [x].[FileId], [f].[Id], [f].[Content], [f].[Name]
FROM [EbooksFiles] AS [x]
INNER JOIN [Files] AS [f] ON [x].[FileId] = [f].[Id]

How can I improve my Linq expression to get only the FileId and Name into a dictionary?

TEST QUERY

var ids = new Int32[] { 1, 2 };

var files = _context
    .EbooksFiles
    .Where(x => ids.Contains(x.EbookId))
    .Select(x => new { x.EbookId, x.File.Name, x.File.Id })
    .GroupBy(x => x.EbookId)
    .ToList();

STACK TRACE

2016-04-29 15:13:40 [Error] An unhandled exception has occurred while executing the request System.InvalidOperationException: Sequence contains more than one element at System.Linq.Enumerable.Single[TSource](IEnumerable1 source) at Microsoft.Data.Entity.Query.EntityQueryModelVisitor.<>c__DisplayClass79_01.b__0(IEnumerable1 ps, IQuerySource qs) at Microsoft.Data.Entity.Query.EntityQueryModelVisitor.BindMemberExpressionCore[TResult](MemberExpression memberExpression, IQuerySource querySource, Func3 memberBinder) at Microsoft.Data.Entity.Query.EntityQueryModelVisitor.BindMemberExpression[TResult](MemberExpression memberExpression, IQuerySource querySource, Func3 memberBinder) at Microsoft.Data.Entity.Query.EntityQueryModelVisitor.BindMemberExpression(MemberExpression memberExpression, Action2 memberBinder) at Microsoft.Data.Entity.Query.ExpressionVisitors.Internal.RequiresMaterializationExpressionVisitor.VisitMember(MemberExpression memberExpression) at System.Linq.Expressions.MemberExpression.Accept(ExpressionVisitor visitor) at Microsoft.Data.Entity.Query.ExpressionVisitors.ExpressionVisitorBase.Visit(Expression expression) at System.Linq.Expressions.ExpressionVisitor.VisitAndConvert[T](ReadOnlyCollection1 nodes, String callerName) at Remotion.Linq.Parsing.RelinqExpressionVisitor.VisitNew(NewExpression expression) at System.Linq.Expressions.NewExpression.Accept(ExpressionVisitor visitor) at Microsoft.Data.Entity.Query.ExpressionVisitors.ExpressionVisitorBase.Visit(Expression expression) at Remotion.Linq.Clauses.ResultOperators.GroupResultOperator.TransformExpressions(Func2 transformation) at Remotion.Linq.QueryModel.TransformExpressions(Func2 transformation) at Microsoft.Data.Entity.Query.ExpressionVisitors.Internal.RequiresMaterializationExpressionVisitor.FindQuerySourcesRequiringMaterialization(QueryModel queryModel) at Microsoft.Data.Entity.Query.QueryCompilationContext.FindQuerySourcesRequiringMaterialization(EntityQueryModelVisitor queryModelVisitor, QueryModel queryModel) at Microsoft.Data.Entity.Query.EntityQueryModelVisitor.CreateQueryExecutor[TResult](QueryModel queryModel) at Microsoft.Data.Entity.Storage.Database.CompileQuery[TResult](QueryModel queryModel) --- End of stack trace from previous location where exception was thrown --- at Microsoft.Data.Entity.Query.Internal.QueryCompiler.<>c__DisplayClass18_01.b__0() at Microsoft.Data.Entity.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func1 compiler) at Microsoft.Data.Entity.Query.Internal.QueryCompiler.CompileQuery[TResult](Expression query) at Microsoft.Data.Entity.Query.Internal.QueryCompiler.Execute[TResult](Expression query) at Microsoft.Data.Entity.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression) at Remotion.Linq.QueryableBase1.GetEnumerator() at System.Collections.Generic.List1..ctor(IEnumerable1 collection) at System.Linq.Enumerable.ToList[TSource](IEnumerable1 source) at EbookGetApiModelHandler.QueryHandler.<Handle>d__4.MoveNext() in \Handlers\EbookGetApiModelHandler.cs:line 85 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at MediatR.Mediator.<SendAsync>d__41.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter1.GetResult() at Controllers.EbookApiController.<Get>d__2.MoveNext() in \Controllers\EbookApiController.cs:line 30 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Mvc.Controllers.ControllerActionExecutor.<CastToObject>d__81.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Mvc.Controllers.ControllerActionInvoker.d__6.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task) at Microsoft.AspNet.Mvc.Controllers.FilterActionInvoker.d__53.MoveNext() --- End of stack trace from previous location where exception was thrown --- at Microsoft.AspNet.Mvc.Controllers.FilterActionInvoker.d__44.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Mvc.Infrastructure.MvcRouteHandler.d__6.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Mvc.Routing.InnerAttributeRoute.d__10.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Routing.RouteCollection.d__9.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Builder.RouterMiddleware.d__4.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Authentication.AuthenticationMiddleware1.<Invoke>d__18.MoveNext() --- End of stack trace from previous location where exception was thrown --- at Microsoft.AspNet.Authentication.AuthenticationMiddleware1.d__18.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Authentication.AuthenticationMiddleware1.<Invoke>d__18.MoveNext() --- End of stack trace from previous location where exception was thrown --- at Microsoft.AspNet.Authentication.AuthenticationMiddleware1.d__18.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Authentication.AuthenticationMiddleware1.<Invoke>d__18.MoveNext() --- End of stack trace from previous location where exception was thrown --- at Microsoft.AspNet.Authentication.AuthenticationMiddleware1.d__18.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Authentication.AuthenticationMiddleware1.<Invoke>d__18.MoveNext() --- End of stack trace from previous location where exception was thrown --- at Microsoft.AspNet.Authentication.AuthenticationMiddleware1.d__18.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Localization.RequestLocalizationMiddleware.d__4.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Diagnostics.Entity.MigrationsEndPointMiddleware.d__5.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Diagnostics.Entity.DatabaseErrorPageMiddleware.d__6.MoveNext() --- End of stack trace from previous location where exception was thrown --- at Microsoft.AspNet.Diagnostics.Entity.DatabaseErrorPageMiddleware.d__6.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Diagnostics.DeveloperExceptionPageMiddleware.d__7.MoveNext()

Answer 1

I think you forgot .Include(x => x.File) in your test query