Incorrect translation of date substraction.

var delays = await db
    .Set<Job>()
    .Select(j => (j.StartJob - j.CreateDate).TotalHours)
    .ToListAsync();

Gets translated into:

SELECT [j].[StartJob] - [j].[CreateDate]
FROM [Job] AS [j]
WHERE [j].[IsDeleted] = 0

Which in turn throws:

System.Data.SqlClient.SqlException (0x80131904): Operand data type datetime2 is invalid for subtract operator.
   at System.Data.SqlClient.SqlCommand.<>c.<ExecuteDbDataReaderAsync>b__108_0(Task`1 result)
   at System.Threading.Tasks.ContinuationResultTaskFromResultTask`2.InnerInvoke()
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.<ExecuteAsync>d__17.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncQueryingEnumerable`1.AsyncEnumerator.<BufferlessMoveNext>d__10.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Storage.Internal.SqlServerExecutionStrategy.<ExecuteAsync>d__7`2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncQueryingEnumerable`1.AsyncEnumerator.<MoveNext>d__9.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.<MoveNext>d__5.MoveNext()
ClientConnectionId:c7a3cc04-ddbf-4aab-9957-7477083c909f
Error Number:8117,State:1,Class:16

This query should either be translated into DateDiff if possible or perform subtraction on client but definitely not throw.

Further technical details

EF Core version: 2.0.1 Database Provider: Microsoft.EntityFrameworkCore.SQLServer Operating system: Windows 10 1703 IDE: Visual Studio 2017

[divega]

@ralmsdeveloper agreed that there are things that would be missing with that approach. That is what I meant when I said “not all of them will work”. That may be a reason the DateDiff extensions methods are still compelling even if only in some databases.

[ErikEJ]

sql-ce fyi?