System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.ImplementEqualityUnknownArguments C# (CSharp) Method

        private DbExpression ImplementEqualityUnknownArguments(DbExpression left, DbExpression right, EqualsPattern pattern)
        {
            switch (pattern)
            {
                case EqualsPattern.Store: // left EQ right
                    return left.Equal(right);
                case EqualsPattern.PositiveNullEqualityNonComposable: // for Joins
                    return left.Equal(right).Or(left.IsNull().And(right.IsNull()));
                case EqualsPattern.PositiveNullEqualityComposable:
                    {
                        var bothNotNull = left.Equal(right);
                        var bothNull = left.IsNull().And(right.IsNull());
                        if (!_funcletizer.RootContext.ContextOptions.UseCSharpNullComparisonBehavior)
                        {
                            return bothNotNull.Or(bothNull); // same as EqualsPattern.PositiveNullEqualityNonComposable
                        }
                        // add more logic to avoid undefined result for true clr semantics, ensuring composability
                        // (left EQ right AND NOT (left IS NULL OR right IS NULL)) OR (left IS NULL AND right IS NULL)
                        var anyOneIsNull = left.IsNull().Or(right.IsNull());
                        return (bothNotNull.And(anyOneIsNull.Not())).Or(bothNull);
                    }
                default:
                    Debug.Fail("unexpected pattern");
                    return null;
            }
        }