Cast int to enum in C#

Question

How can an int be cast to an enum in C#?

Answer 1

This is an flags enumeration aware safe convert method:

public static bool TryConvertToEnum<T>(this int instance, out T result)
  where T: Enum
{
  var enumType = typeof (T);
  var success = Enum.IsDefined(enumType, instance);
  if (success)
  {
    result = (T)Enum.ToObject(enumType, instance);
  }
  else
  {
    result = default(T);
  }
  return success;
}

Answer 2

This parses integers or strings to a target enum with partial matching in dot.NET 4.0 using generics like in Tawani's utility class above. I am using it to convert command-line switch variables which may be incomplete. Since an enum cannot be null, you should logically provide a default value. It can be called like this:

var result = EnumParser<MyEnum>.Parse(valueToParse, MyEnum.FirstValue);

Here's the code:

using System;

public class EnumParser<T> where T : struct
{
    public static T Parse(int toParse, T defaultVal)
    {
        return Parse(toParse + "", defaultVal);
    }
    public static T Parse(string toParse, T defaultVal) 
    {
        T enumVal = defaultVal;
        if (defaultVal is Enum && !String.IsNullOrEmpty(toParse))
        {
            int index;
            if (int.TryParse(toParse, out index))
            {
                Enum.TryParse(index + "", out enumVal);
            }
            else
            {
                if (!Enum.TryParse<T>(toParse + "", true, out enumVal))
                {
                    MatchPartialName(toParse, ref enumVal);
                }
            }
        }
        return enumVal;
    }

    public static void MatchPartialName(string toParse, ref T enumVal)
    {
        foreach (string member in enumVal.GetType().GetEnumNames())
        {
            if (member.ToLower().Contains(toParse.ToLower()))
            {
                if (Enum.TryParse<T>(member + "", out enumVal))
                {
                    break;
                }
            }
        }
    }
}

FYI: The question was about integers, which nobody mentioned will also explicitly convert in Enum.TryParse()

Answer 3

I don't know anymore where I get the part of this enum extension, but it is from stackoverflow. I am sorry for this! But I took this one and modified it for enums with Flags. For enums with Flags I did this:

  public static class Enum<T> where T : struct
  {
     private static readonly IEnumerable<T> All = Enum.GetValues(typeof (T)).Cast<T>();
     private static readonly Dictionary<int, T> Values = All.ToDictionary(k => Convert.ToInt32(k));

     public static T? CastOrNull(int value)
     {
        T foundValue;
        if (Values.TryGetValue(value, out foundValue))
        {
           return foundValue;
        }

        // For enums with Flags-Attribut.
        try
        {
           bool isFlag = typeof(T).GetCustomAttributes(typeof(FlagsAttribute), false).Length > 0;
           if (isFlag)
           {
              int existingIntValue = 0;

              foreach (T t in Enum.GetValues(typeof(T)))
              {
                 if ((value & Convert.ToInt32(t)) > 0)
                 {
                    existingIntValue |= Convert.ToInt32(t);
                 }
              }
              if (existingIntValue == 0)
              {
                 return null;
              }

              return (T)(Enum.Parse(typeof(T), existingIntValue.ToString(), true));
           }
        }
        catch (Exception)
        {
           return null;
        }
        return null;
     }
  }

Example:

[Flags]
public enum PetType
{
  None = 0, Dog = 1, Cat = 2, Fish = 4, Bird = 8, Reptile = 16, Other = 32
};

integer values 
1=Dog;
13= Dog | Fish | Bird;
96= Other;
128= Null;

Answer 4

From a string: (Enum.Parse is out of Date, use Enum.TryParse)

enum Importance
{}

Importance importance;

if (Enum.TryParse(value, out importance))
{
}

Answer 5

Take the following example:

int one = 1;
MyEnum e = (MyEnum)one;

Answer 6

Slightly getting away from the original question, but I found an answer to Stack Overflow question Get int value from enum useful. Create a static class with public const int properties, allowing you to easily collect together a bunch of related int constants, and then not have to cast them to int when using them.

public static class Question
{
    public static readonly int Role = 2;
    public static readonly int ProjectFunding = 3;
    public static readonly int TotalEmployee = 4;
    public static readonly int NumberOfServers = 5;
    public static readonly int TopBusinessConcern = 6;
}

Obviously, some of the enum type functionality will be lost, but for storing a bunch of database id constants, it seems like a pretty tidy solution.