Use of the Enum Description (With Special Characters) in C#

• Download sample - 16.3 KB

Introduction

Can your enums have userfriendly descriptions? How to have enum values with spaces?
What is the use of the enum description (with special characters) in C#?
How can you describe basic convertion extension methods. (Enum.ToDescription(), string.ToEnum<T>())?

Using the Code

Create your enum in your project.

public enum MyEnum1
{
    [DescriptionHelper("[Not selected]")]
    None = 0,
    Video = 1,
    Audio = 2,
    Teletext = 3,
    [DescriptionHelper("DVB Subtitles")]
    DVB_Subtitles = 4,
    ECM = 6,
    Private = 9,
    [DescriptionHelper("AC-3 Audio")]
    AC3_Audio = 10,
    [DescriptionHelper("H.264 Video")]
    H264_Video = 11,
    VBI = 12,
    [DescriptionHelper("AAC Audio")]
    AAC_Audio = 13,
}

Create your attribute class:

namespace EnumSample
{
    public class DescriptionHelperAttribute : Attribute
    {
        public DescriptionHelperAttribute(string description)
        {
            this.Description = description;
        }

        public string Description { get; protected set; }
    }
}

Then include these static extension methods in your code:

namespace EnumSample
{
    public static class MyUtility
    {
        public static T ToEnum<T>(this string s, bool ignoreCase) where T : struct
        {
            Type genericType = typeof(T);
            if (!genericType.IsEnum) return default(T);

            T response;
            if (Enum.TryParse(s, ignoreCase, out response))
            {
                return response;
            }

            Array ary = Enum.GetValues(genericType);
            foreach (T en in ary)
            {
                if ((string.Compare(en.ToString(), s, ignoreCase) == 0) ||
                    (string.Compare((en as Enum).ToDescription(), s, ignoreCase) == 0))
                {
                    return en;
                }
            }

            return default(T);
        }

        public static T ToEnum<T>(this string s) where T : struct
        {
            return s.ToEnum<T>(false);
        }

        public static string[] GetEnumDescriptions<T>() where T : struct
        {
            Type genericType = typeof(T);
            if (!genericType.IsEnum) return new string[0];

            Array ary = Enum.GetValues(genericType);
            string[] strAry = new string[ary.Length];
            int ndx = 0;
            foreach (T en in ary)
            {
                strAry[ndx++] = (en as Enum).ToDescription();
            }
            return strAry;
        }

        public static string ToDescription(this Enum en)
        {
            Type type = en.GetType();

            MemberInfo[] memInfo = type.GetMember(en.ToString());

            if (memInfo != null && memInfo.Length > 0)
            {
                object[] attrs = memInfo[0].GetCustomAttributes(typeof(DescriptionHelperAttribute), false);
                if (attrs != null && attrs.Length > 0)
                {
                    return ((DescriptionHelperAttribute)attrs[0]).Description;
                }
            }

            return en.ToString();
        }
    }
}

Use in the project (Testing):

MyEnum1 en;

// test1
Console.WriteLine();
Console.WriteLine("Test 1) String to enum test...");
Console.WriteLine("   (\"bla bla bla...\").ToEnum<MyEnum1>()");
en = ("bla bla bla...").ToEnum<MyEnum1>();
Console.WriteLine("   \"bla bla bla...\" was not found in MyEnum1! 
However, the result \"{0}\" will be...", default(MyEnum1));
Console.WriteLine("   Result >> Value:\"{0} - {1}\", 
Description:\"{2}\"", (int)en, en.ToString(), en.ToDescription());
Console.WriteLine();

// test2
Console.WriteLine();
Console.WriteLine("Test 2) String to enum test...");
Console.WriteLine("   (\"H.264 Video\").ToEnum<MyEnum1>()");
en = ("H.264 Video").ToEnum<MyEnum1>();
Console.WriteLine("   Result >> Value:\"{0} - {1}\", 
Description:\"{2}\"", (int)en, en.ToString(), en.ToDescription());
Console.WriteLine();

// test3
Console.WriteLine();
Console.WriteLine("Test 3) String to enum test... (Classic 'Enum.Parse' method)");
Console.WriteLine("   (MyEnum1)Enum.Parse(typeof(MyEnum1), \"H.264 Video\")");
Console.WriteLine("   \"H.264 Video\" was not found in MyEnum1! \"H264_Video\" should be...");
Console.WriteLine("   In this example, the classic 'Enum.Parse' method is useless.");
try
{
    en = (MyEnum1)Enum.Parse(typeof(MyEnum1), "H.264 Video");
}
catch (Exception ex)
{
    Console.WriteLine("   Result >> Error[{0:X}] - {1}", ex.HResult, ex.Message);
}
Console.WriteLine();

// test4
Console.WriteLine();
Console.WriteLine("Test 4) GetEnumDescriptions for 'FormWindowState'");
Console.WriteLine("   Result:");
string[] sAry = MyUtility.GetEnumDescriptions<System.Windows.Forms.FormWindowState>();
foreach (string s in sAry)
{
    Console.WriteLine("   >> {0}", s);
}
Console.WriteLine();

This will display:

Test 1) String to enum test...
   ("bla bla bla...").ToEnum<MyEnum1>()
   "bla bla bla..." was not found in MyEnum1! However, the result "None" will be...
   Result >> Value:"0 - None", Description:"[Not selected]"

Test 2) String to enum test...
   ("H.264 Video").ToEnum<MyEnum1>()
   Result >> Value:"11 - H264_Video", Description:"H.264 Video"

Test 3) String to enum test... (Classic 'Enum.Parse' method)
   (MyEnum1)Enum.Parse(typeof(MyEnum1), "H.264 Video")
   "H.264 Video" was not found in MyEnum1! "H264_Video" should be...
   In this example, the classic 'Enum.Parse' method is useless.
   Result >> Error[80070057] - Requested value 'H.264 Video' was not found.

Test 4) GetEnumDescriptions for 'FormWindowState'
   Result:
   >> Normal
   >> Minimized
   >> Maximized

Points of Interest

Why C# doesn't have extension properties? Interesting...

History

• 14^th September, 2014: Initial post