ModuleBuilder.DefineEnum Method (String, TypeAttributes, Type)


Defines an enumeration type that is a value type with a single non-static field called value__ of the specified type.

Namespace:   System.Reflection.Emit
Assembly:  mscorlib (in mscorlib.dll)

public EnumBuilder DefineEnum(
	string name,
	TypeAttributes visibility,
	Type underlyingType


Type: System.String

The full path of the enumeration type. name cannot contain embedded nulls.

Type: System.Reflection.TypeAttributes

The type attributes for the enumeration. The attributes are any bits defined by VisibilityMask.

Type: System.Type

The underlying type for the enumeration. This must be a built-in integer type.

Return Value

Type: System.Reflection.Emit.EnumBuilder

The defined enumeration.

Exception Condition

Attributes other than visibility attributes are provided.


An enumeration with the given name exists in the parent assembly of this module.


The visibility attributes do not match the scope of the enumeration. For example, NestedPublic is specified for visibility, but the enumeration is not a nested type.


name is null.

The defined enum is a derived class of Enum. The value__ field has Private and SpecialName attributes set.

For more information about the built-in integer types that can be specified as the underlying types of enumerations, see .NET Framework Class Library Overview.


In the .NET Framework versions 1.0 and 1.1, it is necessary to define enumerations using TypeBuilder because EnumBuilder emits enumerations whose elements are of type Int32 instead of the enumeration type. In the .NET Framework version 2.0, EnumBuilder emits enumerations whose elements have the correct type.


Starting with the .NET Framework 2.0 Service Pack 1, this member no longer requires ReflectionPermission with the ReflectionPermissionFlag.ReflectionEmit flag. (See Security Issues in Reflection Emit.) To use this functionality, your application should target the .NET Framework 3.5 or later.

The following example illustrates the use of DefineEnum to implement an enumeration class in a dynamic module. The example defines an enumeration named Elevation that has an underlying type of Int32, and creates two elements: Low, with a value of 0, and High, with a value of 1. After the type has been created, the assembly is saved with the name TempAssembly.dll. You can use the Ildasm.exe (IL Disassembler) to examine the contents of this assembly.


Prior to the .NET Framework version 2.0, this code example does not produce a correct enumeration.

using System;
using System.Reflection;
using System.Reflection.Emit;

class Example
    public static void Main()
        // Get the current application domain for the current thread.
        AppDomain currentDomain = AppDomain.CurrentDomain;

        // Create a dynamic assembly in the current application domain, 
        // and allow it to be executed and saved to disk.
        AssemblyName aName = new AssemblyName("TempAssembly");
        AssemblyBuilder ab = currentDomain.DefineDynamicAssembly(
            aName, AssemblyBuilderAccess.RunAndSave);

        // Define a dynamic module in "TempAssembly" assembly. For a single-
        // module assembly, the module has the same name as the assembly.
        ModuleBuilder mb = ab.DefineDynamicModule(aName.Name, aName.Name + ".dll");

        // Define a public enumeration with the name "Elevation" and an 
        // underlying type of Integer.
        EnumBuilder eb = mb.DefineEnum("Elevation", TypeAttributes.Public, typeof(int));

        // Define two members, "High" and "Low".
        eb.DefineLiteral("Low", 0);
        eb.DefineLiteral("High", 1);

        // Create the type and save the assembly.
        Type finished = eb.CreateType();
        ab.Save(aName.Name + ".dll");

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

/* This code example produces the following output:

Elevation.Low = 0
Elevation.High = 1 

.NET Framework
Available since 1.1
Available since 2.0
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