I have a flag enum below.
[Flags]
public enum FlagTest
{
None = 0x0,
Flag1 = 0x1,
Flag2 = 0x2,
Flag3 = 0x4
}
I cannot make the if statement evaluate to true.
FlagTest testItem = FlagTest.Flag1 | FlagTest.Flag2;
if (testItem == FlagTest.Flag1)
{
// Do something,
// however This is never true.
}
How can I make this true?
if ((testItem & FlagTest.Flag1) == FlagTest.Flag1)
{
// Do something
}
(testItem & FlagTest.Flag1) is a bitwise AND operation.
FlagTest.Flag1 is equivalent to 001 with OP's enum. Now let's say testItem has Flag1 and Flag2 (so it's bitwise 101):
001
&101
----
001 == FlagTest.Flag1
I set up an extension method to do it: related question.
Basically:
public static bool IsSet( this Enum input, Enum matchTo )
{
return ( Convert.ToUInt32( input ) & Convert.ToUInt32( matchTo ) ) != 0;
}
Then you can do:
FlagTests testItem = FlagTests.Flag1 | FlagTests.Flag2;
if( testItem.IsSet ( FlagTests.Flag1 ) )
//Flag1 is set
Incidentally the convention I use for enums is singular for standard, plural for flags. That way you know from the enum name whether it can hold multiple values.
For bit operations, you need to use bitwise operators.
This should do the trick:
if ((testItem & FlagTest.Flag1) == FlagTest.Flag1)
{
// Do something,
// however This is never true.
}
Edit: Fixed my if check - I slipped back into my C/C++ ways (thanks to Ryan Farley for pointing it out)
Regarding the edit. You can't make it true. I suggest you wrap what you want into another class (or extension method) to get closer to the syntax you need.
i.e.
public class FlagTestCompare
{
public static bool Compare(this FlagTest myFlag, FlagTest condition)
{
return ((myFlag & condition) == condition);
}
}
Try this:
if ((testItem & FlagTest.Flag1) == FlagTest.Flag1)
{
// do something
}