How to have a set of enumeration values in C#?

问题

Assume i have an enumeration:

namespace System.Windows.Forms
{
   public enum DialogResult { None, OK, Cancel, Abort, Retry, Ignore, Yes, No }
}

i want to declare a "set" made up of these enumerated types

ShowForm(Form frm, DialogResults allowedResults)

In other languages you would declare:

public DialogResults = set of DialogResult;

And then i can use

ShowForm(frm, DialogResult.OK | DialogResult.Retry);

C# has the notion of Flags, pseudocode:

[Flags]
public enum DialogResults { DialogResult.None, DialogResult.OK, DialogResult.Cancel, DialogResult.Abort, DialogResult.Retry, DialogResult.Ignore, DialogResult.Yes, DialogResult.No }

problem with that it's not real code - Flags does not instruct the compiler to create a set of flags.

in one case the type should only allow one value (DialogResult)
in another case the type should allow multiple values of above (DialogResults)

How can i have a "set" of enumerated types?

Note: i assume it's not possible in C#. If that's the answer: it's okay to say so - the question is answered.

Note: Just because i believe C# language doesn't have the feature doesn't mean it doesn't have the feature - i may just not have found it yet.

Update: another example:

Assume i have an enumeration:

public enum PatronTier 
{ 
    Gold = 1,      
    Platinum = 2,  
    Diamond = 3,   
    SevenStar = 7  //Yes, seven
}

i want to declare a "set" made up of these enumerated types

public Tournament
{
   public PatronTiers EligibleTiers { get; set; }
}

In other languages you would declare:

public PatronTiers = set of PatronTier;

And then i can use:

tournament.EligibleTiers = PatronTier.Gold | PatronTier.SevenStar;

C# has the notion of Flags, pseudocode:

[Flags]
public enum PatronTiers { PatronTier.Gold, PatronTier.Platinum, PatronTier.Diamond, PatronTier.SevenStar }

problem with that it's not real code.

How can i have a "set" of enumerated types?

回答1:

Seems like you want an array of things. There are array types in C#, but nothing that is directly equivalent to your examples in terms of compiler support, closest is perhaps DialogResults[], an array of DialogResults.

Try supplying a HashSet of the items you allow. HashSet<T> implements ISet<T>, and it's usually best to work against interfaces than concrete types, especially for method signatures:

ShowForm(Form frm, ISet<DialogResults> allowedResults);

Then you can use Contains to test for items:

if (allowedResults.Contains(DialogResults.OK))
{
}

Somewhat pointless alternative: you could always implement your own Set<Enum> type using Jon Skeet's Unconstrained Melody to give you a nicer syntax from the perspective of the caller and get a little closer to your examples.

回答2:

I don't suppose you just mean using something like this?

var DialogResults = Enum.GetValues(typeof(DialogResult));

with a .Select(dr => (DialogResult)dr).ToArray() if you want it strongly typed.

回答3:

I think you want something like this:

foreach (var item in System.Enum.GetValues(typeof(PatronTier)))
{
    Console.WriteLine(item);
}

来源：https://stackoverflow.com/questions/8523544/how-to-have-a-set-of-enumeration-values-in-c

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