Enum Casting With a Variable

Question

I was hoping to get some help with this. I need a function that can take in a string that is a key for a dictionary and an enum type that is has to be cast to.

The dictionary key will be a number that corresponds to an enum. I need to know how to cast the int into an enum where the enum is variable.

Here is the function as I have it written. This might be more clear than my explanation.

string GetEnum(string keyName, Enum enumType)
{
    var defaultOut = "";
    Model.Form.TryGetValue(keyName, out defaultOut);
    if(defaultOut != ""){
        return EnumDescriptionUtility.GetDescription((enumType)Convert.ToInt32(defaultOut));            
    }
    else{
        return defaultOut;    
    } 
}

I have used most of this code before. the difference before was that enumType was hard coded to the actual enum. I want to offload all that repetition to a function.

Any help is appreciated.

Answer 1

I'm not 100% sure I understand your Q, though if i do, you want to cast a value to a given enum?

This is an extension method I created recently to parse a value to a given enum. The value in this case is the string name of the enum.

public static T ToEnum<T>(this string val) where T : struct
{
     T t;
     if (Enum.TryParse(val, out t))
          return t;
     return default(T);
}

And you would use it like:

public enum MyEnum{
  A = 1,
  B = 2,
  C = 3
}

public enum MyOtherEnum{
  D = 1,
  E = 2,
  F = 3
}


string str = "A";
MyEnum yourEnum = str.ToEnum<MyEnum>();

string str2 = "A";
MyOtherEnum yourOtherEnum = str.ToEnum<MyOtherEnum>();

Answer 2

If you just want to get a string representing the name of the enum for a given type and int, you can do the following using Enum.GetName()

    public enum Letter
    {
        A,
        B,
        C
    }

    public enum Number
    {
        One,
        Two,
        Three
    }

    public static void Main(string[] args)
    {
        int val1 = 2;
        Type type1 = typeof(Letter);
        int val2 = 0;
        Type type2 = typeof(Number);

        var result1 = Enum.GetName(type1, val1);
        var result2 = Enum.GetName(type2, val2);

        Console.WriteLine("result1 {0}", result1);
        Console.WriteLine("result2 {0}", result2);

        Console.ReadKey();
    }

If you want the actual enum, I think you have to do something similar to the other answers. It sounds like you want to cast using a Type variable:

Type type1 = typeof(Letter);
var result = (type1) val1;  // wrong

And I don't think you can do that. Even with generics you will have to specify type at some point.

Answer 3

So if I understand you correctly, you know they type of enum and the integer value. You didn't include any information about your enums so I set up a simple example.

    public enum Letter
    {
        A,
        B,
        C
    }

    public enum Number
    {
        One,
        Two,
        Three
    }

So if you know the type and integer value, you can get an enum like this:

    public static Enum GetEnum(Type type, int val)
    {
        Enum e = null;

        if (type == typeof(Letter))
        {
            e = (Letter)val;
        }
        else if (type == typeof(Number))
        {
            e = (Number)val;
        }

        return e;
    }

You will need to inspect its type to use it. Maybe like this:

    public static string StringFromEnum(Enum e)
    {
        string result = null;

        if (e.GetType() == typeof(Letter))
        {
            result =  ((Letter)e).ToString();
        }
        else if (e.GetType() == typeof(Number))
        {
            result = ((Number)e).ToString();
        }

        return result;
    }

    public static void Main(string[] args)
    {
        int val1 = 2;
        Type type1 = typeof(Letter);
        int val2 = 0;
        Type type2 = typeof(Number);

        var result1 = GetEnum(type1, val1);
        var result2 = GetEnum(type2, val2);

        Console.WriteLine("result1 {0}", StringFromEnum(result1));
        Console.WriteLine("result2 {0}", StringFromEnum(result2));

        Console.ReadKey();
    }