String enumerations in C#

Introduction

I found this article a few months back on CodeProject: stringenum.aspx. It is an impressive, nice way to get enums to carry string values using attributes. After using it, I found myself with a strange need to go the other way round; i.e., given the string value, get the enum value that string is associated with.

Background

I suggest reading the article from the link above first. That article will get you to 90% of the path to "getting strings associated with enums". I am extending the functionality here to go the other way round.

Using the code

//
// Code from http://www.codeproject.com/csharp/stringenum.asp
//
 public class StringEnum
 {
     private Type _enumType;

     /// <summary>
     /// Creates a new <see cref="StringEnum"/> instance.
     /// </summary>
     /// <param name="enumType">Enum type.</param>
     public StringEnum(Type enumType)
     {
         if (!enumType.IsEnum)
            throw new ArgumentException(String.Format(
                      "Supplied type must be an Enum. Type was {0}",
                      enumType.ToString()));

         _enumType = enumType;
    }

    /// <summary>
    /// Gets a string value for a particular enum value.
    /// Developer(s): http://www.codeproject.com/csharp/stringenum.asp,
    /// modified by Kiran Bheemarti
    /// </summary>
    /// <param name="value">Value.</param>
    /// <returns>String Value associated via a
    /// <see cref="StringValueAttribute"/> attribute,
    /// or null if not found.</returns>
    public static string GetStringValue(Enum value)
    {
        Type type = value.GetType();

        //Look for our 'StringValueAttribute' in the field's custom attributes
        FieldInfo fi = type.GetField(value.ToString());
        StringValueAttribute[] attrs = fi.GetCustomAttributes(
          typeof(StringValueAttribute), false) as StringValueAttribute[];

        return (attrs.Length > 0) ? attrs[0].Value : null;
    } 
}

public class StringValueAttribute : Attribute
{
    private string _value;

    /// <summary>
    /// Creates a new <see cref="StringValueAttribute"/> instance.
    /// </summary>
    /// <param name="value">Value.</param>
    public StringValueAttribute(string value)
    {
        _value = value;
    }

    /// <summary>
    /// Gets the value.
    /// </summary>
    /// <value></value>
    public string Value
    {
        get { return _value; }
    }
}

Additional functionality to get enum given string

/// <summary>
/// Gets the Enum given the associated string and the index of the string
/// Developer(s): Kiran Bheemarti
/// </summary>
/// <typeparam name="T"></typeparam>
<param name="value"></param>
/// <returns></returns>
public static T GetEnumForGivenString<T>(string value, int NthOccurence) 
{
    if (!typeof(T).IsEnum)
        throw new ArgumentException(String.Format(
           "Supplied type must be an Enum. Type was {0}",
           typeof(T).ToString()));

    T result = default(T);
    int foundAtIndex = 0;

    foreach (string str in Enum.GetNames(typeof(T)))
    {
        if (GetStringValue((Enum) Enum.Parse(typeof(T), str, true)) == value)
        {
            foundAtIndex++;
            if(foundAtIndex == NthOccurence)
            {
                result = (T)Enum.Parse(typeof(T), str, true);
                break;
            }
        }
    }

    return result;
}

Download the code from the referenced article and add the method given above.