"The operands for operator 'Equal' do not match the parameters of method 'op_Equality'." while using in ?? COALESCE in Where

[blogcraft]

File a bug

When using a COALESCE ?? in a where clause an exception is thrown: The operands for operator 'Equal' do not match the parameters of method 'op_Equality'.

Example:

someFunc(decimal? idX){
    var x = (
            from ta in context.TableA
            join tb in context.TableB on ta.Id equals tb.Id
            where tb.IdX == (idX ?? tb.IdX)
            select ta.SomeValue
        );
}

Include provider and version information

EF Core version: 9.0.0 Database provider: Microsoft.EntityFrameworkCore.SqlServer Target framework: .NET 9.0 Operating system: Windows 11 and Visual Studio 2022 17.12

[cincuranet]

Minimal repro:

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Diagnostics;

using var db = new MyContext();
db.Database.EnsureDeleted();
db.Database.EnsureCreated();

Test(10);
void Test(int? id)
{
    var x = (
                from ta in db.Foos
                join tb in db.Bars on ta.Id equals tb.Id
                where tb.Id == (id ?? tb.Id)
                select ta.Test
            );
    x.Load();
}

public class MyContext : DbContext
{
    public DbSet<Foo> Foos { get; set; }
    public DbSet<Bar> Bars { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.LogTo(Console.WriteLine, events: [RelationalEventId.CommandExecuting]);
        optionsBuilder.UseSqlite("Data Source=test.db");
    }
}

public class Foo
{
    public int Id { get; set; }
    public string? Test { get; set; }
}
public class Bar
{
    public int Id { get; set; }
    public string? Test { get; set; }
}

Full exception:

Unhandled exception. System.InvalidOperationException: The binary operator Equal is not defined for the types 'System.Int32' and 'System.Nullable`1[System.Int32]'.
   at System.Linq.Expressions.Expression.GetEqualityComparisonOperator(ExpressionType binaryType, String opName, Expression left, Expression right, Boolean liftToNull)
   at System.Linq.Expressions.Expression.Equal(Expression left, Expression right, Boolean liftToNull, MethodInfo method)
   at System.Linq.Expressions.Expression.MakeBinary(ExpressionType binaryType, Expression left, Expression right, Boolean liftToNull, MethodInfo method, LambdaExpression conversion)
   at System.Linq.Expressions.BinaryExpression.Update(Expression left, LambdaExpression conversion, Expression right)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.VisitBinary(BinaryExpression binary)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.Visit(Expression expression, State& state)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.VisitLambda[T](Expression`1 lambda)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.Visit(Expression expression, State& state)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.VisitUnary(UnaryExpression unary)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.Visit(Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.Visit[T](ReadOnlyCollection`1 expressions, Func`2 elementVisitor, StateType& aggregateStateType, State[]& expressionStates, Boolean poolExpressionStates)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.Visit(ReadOnlyCollection`1 expressions, StateType& aggregateStateType, State[]& expressionStates, Boolean poolExpressionStates)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.VisitMethodCall(MethodCallExpression methodCall)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.Visit(Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.Visit[T](ReadOnlyCollection`1 expressions, Func`2 elementVisitor, StateType& aggregateStateType, State[]& expressionStates, Boolean poolExpressionStates)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.Visit(ReadOnlyCollection`1 expressions, StateType& aggregateStateType, State[]& expressionStates, Boolean poolExpressionStates)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.VisitMethodCall(MethodCallExpression methodCall)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.Visit(Expression expression, State& state)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.ExtractParameters(Expression expression, IParameterValues parameterValues, Boolean parameterize, Boolean clearParameterizedValues, Boolean precompiledQuery, IReadOnlySet`1& nonNullableReferenceTypeParameters)
   at Microsoft.EntityFrameworkCore.Query.Internal.ExpressionTreeFuncletizer.ExtractParameters(Expression expression, IParameterValues parameterValues, Boolean parameterize, Boolean clearParameterizedValues)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExtractParameters(Expression query, IParameterValues parameterValues, IDiagnosticsLogger`1 logger, Boolean compiledQuery, Boolean generateContextAccessors)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExecuteCore[TResult](Expression query, Boolean async, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1.GetEnumerator()
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.Load[TSource](IQueryable`1 source)

[roji]

Confirmed that the repro above no longer errors when executed against #35122, so this is a duplicate of #35095.

[roji]

Duplicate of #35095.

[blogcraft]

Hi! Is this something that will be fixed in a near parch? O should I have to rewrite all my code to be able to update to EF Core 9?

😱

I also could not find any docs mentioning this breaking change.

[roji]

@blogcraft there's a very good chance this will be patched, yes; in the meantime see #35095 for a workaround.

This isn't listed as a breaking change because it's an unintentional bug (which will get fixed). The docs list out intentional breaking changes, not bugs.