"c like" bitwise-or'ing api toggles for function parameters

Question

What's the best way of providing toggles to a function call in c# ? similar to how it is done in C/C++. I want to be able to add additional toggles without breaking the API. The ideal solution requires the least LOC.

E.g., in C we can do FILE_OPEN | FILE_READONLY.

You mean using Flags Enum? http://www.dotnetperls.com/enum-flags — Tommaso Belluzzo, Jan 16 '13 at 13:48
I have edited your title. Please see, "[Should questions include “tags” in their titles?](http://meta.stackexchange.com/questions/19190/)", where the consensus is "no, they should not". — John Saunders, Jan 16 '13 at 13:49
The `flags` attribute does very nearly nothing. You can OR together members of a normal enum, too - that just confuses ToString. — harold, Jan 16 '13 at 13:53
Take a look a this other question http://stackoverflow.com/questions/8447/enum-flags-attribute — Jose Lamas Ríos, Jan 16 '13 at 13:53

score 2 · Accepted Answer · answered Jan 16 '13 at 13:50

2

You mean using Flags Enum? Here is a little tutorial with snippets: http://www.dotnetperls.com/enum-flags Example:

class Program
{

    [Flags]
    public enum MyFlags
    {
        Foo = 0x1,
        Bar = 0x2,
        Baz = 0x4
    }

    static void Main(string[] args)
    {
        MyFlags fooBar = MyFlags.Foo | MyFlags.Bar;

        if (fooBar.HasFlag(MyFlags.Foo))
            Console.WriteLine("Item has Foo flag set");
    }
}

answered Jan 16 '13 at 13:50

Tommaso Belluzzo

23,232
8
74
98

wish it had implicit power-of-two numbering :D – Hassan Syed Jan 16 '13 at 14:09

score 1 · Answer 2 · answered Jan 16 '13 at 13:50

1

Whilst you can use flags enum, I personally find that using bitwise operators for set operations is somewhat unclean. You could use HashSet<MyEnum>. Add members to the set with Add, and test for membership with Contains.

But it still makes for a mess at the call site. This is one area where C# is weak in comparison with many other languages. Ideally there should be a set type built into the language that supported an in operator to test for membership.

answered Jan 16 '13 at 13:50

David Heffernan

601,492
42
1,072
1,490

I didn't want to do something like that, that is introducing a dynamic construct to solve a compile time problem. It is quite robust though. +1. – Hassan Syed Jan 16 '13 at 13:51

"c like" bitwise-or'ing api toggles for function parameters

2 Answers2