using System;

public class Program

{

    public void Main()

    {

        var resultWeekday = ToEnum("St");

        var resultShort = ToShort(Weekday.Friday);

        Console.WriteLine(resultWeekday);

        Console.WriteLine(resultShort);

    }

    public enum Weekday

    {

        [ShortName("Mo")]

        Monday,

        [ShortName("Tue")]

        Tuesday,

        [ShortName("Wd")]

        Wednesday,

        [ShortName("Thu")]

        Thursday,

        [ShortName("Fr")]

        Friday,

        [ShortName("St")]

        Saturday,

        [ShortName("Sn")]

        Sunday

    }

    public string ToShort(Weekday enumValue)

    {

        var type = enumValue.GetType();

        var fieldInfo = type.GetField(enumValue.ToString());

​

        var attr = fieldInfo.GetCustomAttributes(typeof(ShortName), false) as ShortName[];

        if(attr.Length > 0)

        {

            return attr[0].Name;

        }

        return "";

    }

    public Weekday ToEnum(string shortString)

    {

        var type = typeof(Weekday);

        foreach(var field in type.GetFields())

        {

            var attribute = Attribute.GetCustomAttribute(field, typeof(ShortName)) as ShortName;

            if(attribute != null)

            {

                if(attribute.Name == shortString)

                    return (Weekday)field.GetValue(null);

            }

        }

        throw new ArgumentException("Not found", shortString);

    }

}

​

public class ShortName : Attribute

{

    private string _name; // no need for underline

​

    public ShortName(string name)

    {

        this._name = name;

    }

    public string Name 

    {

        get{return _name;}

    }

}

​

​