The extension method below returns a mask from a list of Enum values.
public static T ToMask<T>(this IEnumerable<T> values) where T : struct, IConvertible
{
if (!typeof(T).IsEnum)
throw new ArgumentException("T must be an enumerated type.");
int builtValue = 0;
foreach (T value in Enum.GetValues(typeof(T)))
{
if (values.Contains(value))
{
builtValue |= Convert.ToInt32(value);
}
}
return (T)Enum.Parse(typeof(T), builtValue.ToString());
}
The extension method below returns a list of Enum values from a mask.
public static IEnumerable<T> ToValues<T>(this T flags) where T : struct, IConvertible
{
if (!typeof(T).IsEnum)
throw new ArgumentException("T must be an enumerated type.");
int inputInt = (int)(object)(T)flags;
foreach (T value in Enum.GetValues(typeof(T)))
{
int valueInt = (int)(object)(T)value;
if (0 != (valueInt & inputInt))
{
yield return value;
}
}
}
Note that:
- Generic constraints in c# (
where T : ...
) cannot restrict T to an Enum - These methods do not check whether the Enum has the
[Flags]
attribute (could not figure that out)
Usage:
[Flags]
public enum TestEnum : int
{
None = 0,
Plop = 1,
Pouet = 2,
Foo = 4,
Bar = 8
}
To mask:
TestEnum[] enums = new[] { TestEnum.None, TestEnum.Plop, TestEnum.Foo };
TestEnum flags = enums.ToMask();
TestEnum expectedFlags = TestEnum.None | TestEnum.Plop | TestEnum.Foo;
Assert.AreEqual(expectedFlags, flags);
To values:
TestEnum flags = TestEnum.None | TestEnum.Plop | TestEnum.Foo;
TestEnum[] array = flags.ToValues().ToArray();
TestEnum[] expectedArray = new[] { TestEnum.Plop, TestEnum.Foo };
CollectionAssert.AreEqual(expectedArray, array);