// Generate an equality expression with one unknown operator and
private DbExpression ImplementEqualityConstantAndUnknown(
DbConstantExpression constant, DbExpression unknown, EqualsPattern pattern)
{
switch (pattern)
{
case EqualsPattern.Store:
case EqualsPattern.PositiveNullEqualityNonComposable: // for Joins
return constant.Equal(unknown); // either both are non-null, or one is null and the predicate result is undefined
case EqualsPattern.PositiveNullEqualityComposable:
if (!_funcletizer.RootContext.ContextOptions.UseCSharpNullComparisonBehavior)
{
return constant.Equal(unknown); // same as EqualsPattern.PositiveNullEqualityNonComposable
}
return constant.Equal(unknown).And(unknown.IsNull().Not());
// add more logic to avoid undefined result for true clr semantics
default:
Debug.Fail("unknown pattern");
return null;
}
}