c# Get all enum values greater than a given value?

Question

I have the following enumeration of membership roles:

public enum RoleName
{
    RegisteredUser,
    Moderator,
    Administrator,
    Owner
}

I want to be able to fetch all roles greater than or equal to a given role.

For instance I input Administrator and I get an IEnumerable with RoleName.Administration and RoleName.Owner

Something of this sort:

public static void AddUserToRole(string username, RoleName level)
{
    var roles = Enum.GetValues(typeof(RoleName)).Cast<R>().ToList().Where(role => level > role);

    foreach (var role in roles)
    {
        Roles.AddUserToRole(username, role);
    }
}

considering that enum as default is of INT type, isn't enough to compare values against filter int? — Tigran
– Tigran, Commented Jul 24, 2011 at 15:53

Ramūnas · Accepted Answer · 2020-01-16 17:46:59Z

25

Probably depending on version of .NET. But this works very well for me:

There is no need to convert or to use special tricks. Just compare with the usual operators:

using System;

enum Test { a1, a2, a3, a4 }

class Program
{
    static void Main(string[] args)
    {
        Test a = Test.a2;

        Console.WriteLine((a > Test.a1));
        Console.WriteLine((a > Test.a2));
        Console.WriteLine((a > Test.a3));
        Console.WriteLine((a > Test.a4));

        Console.ReadKey();
    }
}

Output:

True
False
False
False

edited Jan 16, 2020 at 17:46

Ramūnas

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answered Feb 19, 2014 at 11:05

Bitterblue

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Comments

nakhli · Accepted Answer · 2011-07-24 15:59:26Z

21

You can use the following helper method to give you a set of roles allowed for a given role:

    private IEnumerable<RoleName> AllAllowedRoles(RoleName level)
    {
        return Enum.GetValues(typeof(RoleName)).Cast<RoleName>().Where(role => level >= role);
    }

And then assign all of them to the user.

answered Jul 24, 2011 at 15:59

nakhli

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Comments

Mo Valipour · Accepted Answer · 2011-07-24 16:01:17Z

7

in order to have a better definition of which role is greater than the other you need to assign numeric values to your roles like this:

public enum RoleName
{
    RegisteredUser = 2,
    Moderator = 4,
    Administrator = 8,
    Owner = 16
}

Now if you cast any instance of type RoleName to (int) you will get the numeric value and therefore you will be able to compare them against each other.

Note:
1. Here I use powers of 2 as values to allow combining RoleNames using bit-wise operators.

edited Jul 24, 2011 at 16:01

answered Jul 24, 2011 at 15:55

Mo Valipour

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3 Comments

SLaks Over a year ago

Wrong; you don't need to assign any values.

Mo Valipour Over a year ago

true that but as I said: in order to have a "better definition". otherwise you can easily get confused. but by giving them values you can always quickly judge that.

nakhli Over a year ago

Not sure using flags here is a good idea. most of the combinations are meaningless eg. Owner | RegisteredUser.

bevacqua · Accepted Answer · 2011-07-24 16:17:19Z

2

went with this:

    public static void AddUserToRole(string username, RoleName level)
    {
        var roles = RolesLesserThanOrEqualTo(level);

        foreach (var role in roles)
        {
            Roles.AddUserToRole(username, role.Name());
        }
    }

    public static IEnumerable<RoleName> RolesLesserThanOrEqualTo(RoleName level)
    {
        return Enum.GetValues(typeof(RoleName)).Cast<RoleName>().Where(role => level >= role);
    }

answered Jul 24, 2011 at 16:17

bevacqua

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Comments

SLaks · Accepted Answer · 2011-07-24 15:56:11Z

0

Your code is exactly correct, except that you need to Cast<int>() and you don't need ToList().

answered Jul 24, 2011 at 15:56

SLaks

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Comments

Community · Accepted Answer · 2017-05-23 12:03:05Z

0

public enum RoleName : int
{
    RegisteredUser = 7,
    Moderator = 8,
    Administrator = 9,
    Owner = 10
}

 public List<RoleName> GetGreaterOrEqual(RoleName role)
    {
        List<RoleName> list = new List<RoleName>();
        foreach (RoleName rn in Enum.GetValues(typeof(RoleName)))
        {
            if(rn >= role)
                list.Add(rn);
        }
        return list;
    }

You could check this out Can you loop through all enum values?

edited May 23, 2017 at 12:03

CommunityBot

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answered Jul 24, 2011 at 16:01

psu

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Comments

jason · Accepted Answer · 2011-07-24 16:09:47Z

0

You have to take into consideration the underlying type of the enum. Thus:

static IEnumerable<T> Get<T>(T value) where T : struct {
    Type underlyingType = Enum.GetUnderlyingType(typeof(T));
    var compareToMethod = underlyingType.GetMethod(
                              "CompareTo",
                              new[] { underlyingType }
                          );
    var values = Enum.GetValues(typeof(T));
    for (int index = 0; index < values.Length; index++) {
        int comparison = (int)compareToMethod.Invoke(
            Convert.ChangeType(value, underlyingType),
            new object[] { values.GetValue(index) }
        );
        if (comparison >= 0) {
            yield return (T)values.GetValue(index);
        }
     }
 }

I didn't feel like trying to come up with a good name, but this works:

var largerValues = Get<RoleName>(RoleName.Moderator);
foreach(var largerValue in largerValues) {
    Console.WriteLine(largerValue);
}

answered Jul 24, 2011 at 16:09

jason

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2 Comments

bevacqua Over a year ago

Is reflection really the best way to go?

jason Over a year ago

@Nico: If you want it to be general, yes. If you want it ONLY for RoleName, no.

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