Union not supported?

SQL has a UNION operator. So I’m not sure I understand why Union() doesn’t appear to work.

var test = await DbContext.StorageAdjustments
    .Select(a => new StorageUpdateModel
    {
        TimeStamp = a.TimeStamp,
        Change = a.Volume,
        Volume = 0,
        Product = a.Product.Name,
        UpdateType = StorageUpdateType.Adjustment,
        Notes = $"{a.UserName}{(!string.IsNullOrWhiteSpace(a.Comments) ? $" : {a.Comments}" : null)}",
    })
    .Union(DbContext.StorageTrucks
        .Select(t => new StorageUpdateModel
        {
            TimeStamp = t.TimeStamp,
            Change = t.Volume,
            Volume = 0,
            Product = null,
            UpdateType = StorageUpdateType.Truck,
            Notes = $"BOL {t.Truck.FormattedBol}",
        }))
    .ToListAsync();

System.InvalidOperationException: 'Unable to translate set operation after client projection has been applied. Consider moving the set operation before the last 'Select' call.'
   at Microsoft.EntityFrameworkCore.Query.SqlExpressions.SelectExpression.ApplySetOperation(SetOperationType setOperationType, SelectExpression select2, Boolean distinct)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryableMethodTranslatingExpressionVisitor.TranslateUnion(ShapedQueryExpression source1, ShapedQueryExpression source2)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.QueryCompilationContext.CreateQueryExecutor[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass12_0`1.<ExecuteAsync>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExecuteAsync[TResult](Expression query, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.ExecuteAsync[TResult](Expression expression, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1.GetAsyncEnumerator(CancellationToken cancellationToken)
   at System.Runtime.CompilerServices.ConfiguredCancelableAsyncEnumerable`1.GetAsyncEnumerator()
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.<ToListAsync>d__65`1.MoveNext()
   at Pegasus.Pages.Transloading.StorageLocations.DetailsModel.<OnGetAsync>d__15.MoveNext() in D:\Users\jwood\source\repos\Railtrax\Pegasus\Pages\Transloading\StorageLocations\Details.cshtml.cs:line 64

EF Core version: 6.06 Database provider: Microsoft.EntityFrameworkCore.SqlServer Target framework: .NET 6.0 Operating system: Windows 11 IDE: Visual Studio 2022 17.3.2)

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Thanks for the link. I wouldn’t assume that the plan/memory warning regarding CONVERT necessarily affects your case; at the very least I’d analyze the specific SQL here and see if the same warning is issued.

In any case, this is basically a dup of #19129 (and very specifically of https://github.com/dotnet/efcore/issues/19129#issuecomment-824148525).

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This isn’t related to the strings being different lengths is it?

No, definitely shouldn’t be. It should be the database type of one of the column there (Timestamp, Volume…). I’d put my money on a.Product.Name, which you’re trying to join with an empty string literal - try removing pairs until you isolate which one it is.