c# enum flag check if string is in flag

Question

I have an enum:

[Flags]
public enum WeekDays
{

    Monday = 1,
    Tuesday = 2,
    Wednesday = 4,
    Thursday = 8,
    Friday = 16,
    Saturday = 32,
    Sunday = 64
}

And if I do:

var weekDays = WeekDays.Monday | WeekDays.Tuesday | WeekDays.Friday;

How can I check if a string for example Monday is set in the weekDays?

Which bit's not working for you? Parsing a string, or checking if the relevant bit is set in a variable? — Rowland Shaw
– Rowland Shaw, Commented Aug 27, 2015 at 20:48

CodeLikeBeaker · Accepted Answer · 2015-08-27 21:14:03Z

3

Check out the following code. You can use the HasFlag attribute:

class Program
    {
        [Flags]
        public enum WeekDays
        {

            Monday = 1,
            Tuesday = 2,
            Wednesday = 4,
            Thursday = 8,
            Friday = 16,
            Saturday = 32,
            Sunday = 64
        }

        private static string result;

        static void Main()
        {
            var wd = new WeekDays();
            Console.WriteLine(wd.HasFlag(WeekDays.Monday));

            wd = WeekDays.Monday;

            Console.WriteLine(wd.HasFlag(WeekDays.Monday));

            bool is_defined = Enum.IsDefined(typeof(WeekDays), "Monday");

            Console.WriteLine(is_defined);

            bool is_not_defined = Enum.IsDefined(typeof(WeekDays), "Mondays");

            Console.WriteLine(is_not_defined);

            bool has_flag_by_string = Enum.TryParse<WeekDays>("Monday", out wd);

            Console.WriteLine(has_flag_by_string);

            Console.ReadLine();
        }
    }

EDIT

Added the ability to check if attribute exists by string.

EDIT 2

Added the Enum.TryParse<> to parse the string value.

Reference:

https://msdn.microsoft.com/en-us/library/system.enum.hasflag(v=vs.110).aspx

edited Aug 27, 2015 at 21:14

answered Aug 27, 2015 at 20:48

CodeLikeBeaker

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4 Comments

juharr Over a year ago

I think the OP is saying how do they know that given the string "Monday" that the corresponding enum value is set in a give WeekDays value.

CodeLikeBeaker Over a year ago

@juharr added the TryParse to get what he want based on your comment.

juharr Over a year ago

FYI you don't have to include the generic type in the TryParse call as it will be inferred from the out parameter.

CodeLikeBeaker Over a year ago

Very true, I do it out of habit and readability so I know what Type I'm working with.

juharr · Accepted Answer · 2015-08-27 21:10:18Z

2

I think you want this

WeekDays days = WeekDays.Monday | WeekDays.Tuesday;

string monday = "Monday";

WeekDays day;
if (Enum.TryParse(monday, true, out day))
{
    if (days.HasFlag(day))
    {
        Console.WriteLine("Has {0}", monday);
    }
    else
    {
        Console.WriteLine("Does not have {0}", monday);
    }
}
else
{
    Console.WriteLine("invalid string");
}

First you can use Enum.TryParse to parse the string to an enum value or determine if the string is invalid. Then use HasFlag to see if it is included.

answered Aug 27, 2015 at 21:10

juharr

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