Linq.Except with Func parameter (aka Where not)

[Thaina]

When we have write complex logic in Linq and want it to inverse selection easily

var filter = array.Where((item) => {
    switch(enumValue)
    {
        case 1: return !item.Condition1;
        case 2: return !item.Condition2;
        case 3: return !item.Condition3;
    }

    if(anotherCondition)
        return !(item.Condition1 || item.Condition2 || item.Condition3);

    // more complex logic for other conditions and etc
});

Sometimes most of the logic need to be false. So it more clean to have inverse Where clause

I think Except would do. While currently it accept another enumerable as parameter. If it overload to accept func it would be useful

var filter = array.Except((item) => {
    switch(enumValue)
    {
        case 1: return item.Condition1;
        case 2: return item.Condition2;
        case 3: return item.Condition3;
    }

    if(anotherCondition)
        return item.Condition1 || item.Condition2 || item.Condition3;

    // more complex logic for other conditions and etc
});

Even a short logic could be optimized

Func<object,bool> filter;

var filtered = array.Where((item) => !filter(item));
// became
var filtered = array.Except(filter);

[eiriktsarpalis]

Local methods are your friend:

var filter = array.Where(item => {
    return !ComplexPredicate(item);

    bool ComplexPredicate(Foo item)
    {
        switch (enumValue)
        {
            case 1: return item.Condition1;
            case 2: return item.Condition2;
            case 3: return item.Condition3;
        }

        if (anotherCondition)
            return item.Condition1 || item.Condition2 || item.Condition3;
    }
});

[Clockwork-Muse]

Also, note that Except specifically is one of the "set operations", and removes duplicates, which probably isn't desired behavior.

[eiriktsarpalis]

I'm going to close this issue, since I don't feel it meets the bar for inclusion to System.Linq. Feel free to reopen if you would like the conversation to continue.