I have a flags enum defined like this:
[Flags]
public enum MyEnum
{
None = 0x00,
Choice1 = 0x01,
Choice2 = 0x02,
Choice3 = 0x04,
Default = Choice1 | Choice2,
All = Default | Choice3
}
I would like a way to print out which flags are included in MyEnum.Default
. In this case, I'd want the output to be something like "Choice1, Choice2".
The problem with simply printing MyEnum.Default.ToString()
is that the output would be "Default" when I want "Choice1, Choice2".
Here's one option, but if I used this I'd have to update the printing every time I changed the enum.
((StudyData.Choice1 & StudyData.Default) == StudyData.Choice1 ? StudyData.Choice1.ToString() : "") + ", " +
((StudyData.Choice2 & StudyData.Default) == StudyData.Choice2 ? StudyData.Choice2.ToString() : "") + ", " +
((StudyData.Choice3 & StudyData.Default) == StudyData.Choice3 ? StudyData.Choice3.ToString() : "")
Does anyone have a cleaner way of doing this? Ideally, I'd like a way of printing out the flags included in MyEnum.Default
without having to change the printing code every time I added a new flag or changed the default.
Thanks!
Using the extension methods I've written here on a related question, this should be simple:
var value = MyEnum.Default;
var str = String.Join(", ", value.GetIndividualFlags());
// "Choice1, Choice2"
And here's the extension methods:
static class EnumExtensions
{
public static IEnumerable<Enum> GetFlags(this Enum value)
{
return GetFlags(value, Enum.GetValues(value.GetType()).Cast<Enum>().ToArray());
}
public static IEnumerable<Enum> GetIndividualFlags(this Enum value)
{
return GetFlags(value, GetFlagValues(value.GetType()).ToArray());
}
private static IEnumerable<Enum> GetFlags(Enum value, Enum[] values)
{
ulong bits = Convert.ToUInt64(value);
List<Enum> results = new List<Enum>();
for (int i = values.Length - 1; i >= 0; i--)
{
ulong mask = Convert.ToUInt64(values[i]);
if (i == 0 && mask == 0L)
break;
if ((bits & mask) == mask)
{
results.Add(values[i]);
bits -= mask;
}
}
if (bits != 0L)
return Enumerable.Empty<Enum>();
if (Convert.ToUInt64(value) != 0L)
return results.Reverse<Enum>();
if (bits == Convert.ToUInt64(value) && values.Length > 0 && Convert.ToUInt64(values[0]) == 0L)
return values.Take(1);
return Enumerable.Empty<Enum>();
}
private static IEnumerable<Enum> GetFlagValues(Type enumType)
{
ulong flag = 0x1;
foreach (var value in Enum.GetValues(enumType).Cast<Enum>())
{
ulong bits = Convert.ToUInt64(value);
if (bits == 0L)
//yield return value;
continue; // skip the zero value
while (flag < bits) flag <<= 1;
if (flag == bits)
yield return value;
}
}
}