Create an enum at runtime

  • Thread starter Thread starter Lawrence Oluyede
  • Start date Start date
L

Lawrence Oluyede

I have a list of strings and i'd like to build up an
enum from them... is there a way to do that?

Thanks in advance.
 
I'm able to create an enum at runtime and fill it with the values that i
need but the problem arises when i want to use that enumeration...

....I'd like that the user of the class could do something like this:

FooClass fc = new FooClass();

fc.FooMethod(Foos.FirstFoo);

where Foos is the enumeration I build at runtime when FooClass is instantiated
and FirstFoo is one of its fields... how can i do that?
 
You probably want to build the enums at compile time.. if you are using
Visual Studio you could generate them with a pre-build event. Otherwise
there's really no advantage to generating them, IMO.

Richard
 
Richard A. Lowe said:
You probably want to build the enums at compile time.. if you are using
Visual Studio you could generate them with a pre-build event. Otherwise
there's really no advantage to generating them, IMO.
Click to expand...

Yes, I'm using VS.NET, but what do you mean with "generate the with a prebuild
event?"
 
You can run an executable before VS.NET builds your code - it's under the
project properties-->Common Properties-->Build Events. You would have to
develop the app that generated your enum, of course, but you could easily
run it by entering it's command line as the Pre-build event.

R.
 
Hi Lawrence,

What exactly is the issue? Are you getting any error message or just
need some background on using enums in general?

If the latter please review the following example which is pulled
directly from msdn (http://msdn.microsoft.com/library/d...ry/en-us/csspec/html/vclrfcsharpspec_14_3.asp)

using System;
enum Color
{
Red,
Green = 10,
Blue
}
class Test
{
static void Main() {
Console.WriteLine(StringFromColor(Color.Red));
Console.WriteLine(StringFromColor(Color.Green));
Console.WriteLine(StringFromColor(Color.Blue));
}
static string StringFromColor(Color c) {
switch (c) {
case Color.Red:
return String.Format("Red = {0}", (int) c);
case Color.Green:
return String.Format("Green = {0}", (int) c);
case Color.Blue:
return String.Format("Blue = {0}", (int) c);
default:
return "Invalid color";
}
}
}


~~~~~~~~~~~~~
Tommie Carter
 
What exactly is the issue? Are you getting any error message or just
need some background on using enums in general?
Click to expand...

No :) I think that I'm able to use enums but I'm not able to create them
at runtime... here's some code to explain what i mean:

AppDomain domain = Thread.GetDomain();
AssemblyName name = new AssemblyName();
name.Name = "EnumAssembly";
AssemblyBuilder asmBuilder = domain.DefineDynamicAssembly(
name, AssemblyBuilderAccess.Run);
ModuleBuilder modBuilder = asmBuilder.DefineDynamicModule("EnumModule");
EnumBuilder enumBuilder = modBuilder.DefineEnum("Language",
TypeAttributes.Public,
typeof(System.Int32));

for(int i = 0; i < al.Count; i++)
// here al is an array list with a list of string values
enumBuilder.DefineLiteral(al.ToString(), i);

Type enumType = enumBuilder.CreateType();

Enum enumObj = (Enum) Activator.CreateInstance(enumType);

// here is an example
enumType.GetField("ar-SA").SetValue(enumObj, 1);


What I'd like to is that when a dev use the class containing such code
could use enumObj like a normal enum AA { a, b, c }

Bye
 
Hi Lawrence,

I have taken some time to put together the example so that I could
gain a better understanding of what you are attempting to do -- so
here is what I saw (hope it matches your intent).

using System;
using System.Threading;
using System.Reflection;
using System.Reflection.Emit;
namespace EnumTest1
{
/// <summary>
/// Summary description for Class1.
/// </summary>
class Class1
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main(string[] args)
{
AppDomain domain = Thread.GetDomain();
AssemblyName name = new AssemblyName();
name.Name = "EnumAssembly";
AssemblyBuilder asmBuilder = domain.DefineDynamicAssembly(
name, AssemblyBuilderAccess.Run);
ModuleBuilder modBuilder =
asmBuilder.DefineDynamicModule("EnumModule");
EnumBuilder enumBuilder = modBuilder.DefineEnum("Language",
TypeAttributes.Public,
typeof(System.Int32));
string[] al={"en-US","en-UK","ar-SA","da-DK","French","Cantonese"};
for(int i = 0; i < al.Length; i++)
{
// here al is an array list with a list of string values
enumBuilder.DefineLiteral(al.ToString(), i);
}
Type enumType = enumBuilder.CreateType();
Enum enumObj = (Enum) Activator.CreateInstance(enumType);
// here is an example
try
{
enumType.GetField("en-US").SetValue(enumObj, 1);
}
catch( Exception e )
{
// Any exception generated is displayed.
Console.WriteLine( "Exception: {0}", e.Message );
}


}
}
}


The only error I get is when we try to set the field value using the
enumObj (which is just an instance of the enum struct with the default
enum only)

The error is:

"Cannot set a final field"

I guess I'm not sure that you can set an enum in the same manner
as you'd set a field value (at least within the context of using this
function).

I see no reason why a developer could not legitimately use the
enums defined in the module that you created...

An alternative to trying to set the field of the object might be
to pass data between application domains using the SetData and GetData
methods of the AppDomain class (to pass the values for the Language
enum).

Good Luck,
~~~~~~~~~~~~~
Tommie Carter
www.premiertechnology.com
--
Lawrence Oluyede said:
What exactly is the issue? Are you getting any error message or just
need some background on using enums in general?
Click to expand...

No :) I think that I'm able to use enums but I'm not able to create them
at runtime... here's some code to explain what i mean:

AppDomain domain = Thread.GetDomain();
AssemblyName name = new AssemblyName();
name.Name = "EnumAssembly";
AssemblyBuilder asmBuilder = domain.DefineDynamicAssembly(
name, AssemblyBuilderAccess.Run);
ModuleBuilder modBuilder = asmBuilder.DefineDynamicModule("EnumModule");
EnumBuilder enumBuilder = modBuilder.DefineEnum("Language",
TypeAttributes.Public,
typeof(System.Int32));

for(int i = 0; i < al.Count; i++)
// here al is an array list with a list of string values
enumBuilder.DefineLiteral(al.ToString(), i);

Type enumType = enumBuilder.CreateType();

Enum enumObj = (Enum) Activator.CreateInstance(enumType);

// here is an example
enumType.GetField("ar-SA").SetValue(enumObj, 1);


What I'd like to is that when a dev use the class containing such code
could use enumObj like a normal enum AA { a, b, c }

Bye
Click to expand...
 
// here is an example
try
{
enumType.GetField("en-US").SetValue(enumObj, 1);
}
catch( Exception e )
{
// Any exception generated is displayed.
Console.WriteLine( "Exception: {0}", e.Message );
}
Click to expand...

Thanks Tom, I think you've understood but my question still remains
up there... enumType.GetField("en-US").SetBlablah is not a wonderful
way to use an enum. What i want to know if it could be done is:
can I use enumObj like a standard compile time enum (I mean typing
enumObj.en-US)?

Thanks for your help Tom.
 
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