Fill/update the enum values at runtime in C#

Question

I have windows app where-in i need to fill enum values at runtime by reading a text file named "Controls.txt". As restriction, i'm not suppose to use dictionary. Below is the default values available in the enum MyControls. I have to use enums only.

public enum MyControls
{
   Button1 = 0,
   Button2 = 1,
   Button3 = 2,
}

If Controls.txt file is available, then content of enum should change like

public enum MyControls
{
   btn1 = 0,
   btn2 = 1,
   btn3 = 2,
}

how do i achieve this. I also came across the link Creating / Modifying Enums at Runtime but could not get idea.

Answer 1

I strongly think you are trying to solve the wrong problem. The value of enum is type-safety. I do not think that filling it up dynamically is a good idea. What would really be useful is to have an enum populated by a text file (for example) even before compilation. You can do this using text templates in VS.

You can find an example in my blog post here: http://skleanthous.azurewebsites.net/post/2014/05/21/Creating-enums-from-the-database-and-using-them-in-Entity-framework-5-and-later-in-model-first

Although my example loads from a db, changing it to load from a text file should be trivial.

Answer 2

Apart from the fact that i agree with the other answer that says that you lose type and compile time safety, using EnumBuilderClass should be the only way (thanks to huMpty duMpty's comment).

// sample "file":
string fileContent = @"
btn1 = 0,
btn2 = 1,
btn3 = 2,
";
var enumBody = fileContent.Split(new[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries)
    .Select(line => new { bothToken = line.Trim().Trim(',').Split('=') })
    .Where(x => x.bothToken.Length == 2)
    .Select(x => new { Name = x.bothToken[0].Trim(), Value = int.Parse(x.bothToken[1].Trim()) });

AppDomain currentDomain = AppDomain.CurrentDomain;
AssemblyName asmName = new AssemblyName("EnumAssembly");
AssemblyBuilder asmBuilder = currentDomain.DefineDynamicAssembly(asmName, AssemblyBuilderAccess.RunAndSave);
ModuleBuilder mb = asmBuilder.DefineDynamicModule(asmName.Name, asmName.Name + ".dll");
string enumTypeName = string.Format("{0}.{1}", typeof(MyControls).Namespace, typeof(MyControls).Name);
EnumBuilder eb = mb.DefineEnum(enumTypeName, TypeAttributes.Public, typeof(int));
foreach(var element in enumBody)
{
    FieldBuilder fb1 = eb.DefineLiteral(element.Name, element.Value);
}
Type eType = eb.CreateType();

foreach (object obj in Enum.GetValues(eType))
{
    Console.WriteLine("{0}.{1} = {2}", eType, obj, ((int)obj));
}

Output:

Namespacename.MyControls.btn1 = 0
Namespacename.MyControls.btn2 = 1
Namespacename.MyControls.btn3 = 2