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AppDomain.DefineDynamicAssembly Method (AssemblyName, AssemblyBuilderAccess, PermissionSet, PermissionSet, PermissionSet)

obsoleteCodeEntityM:System.AppDomain.DefineDynamicAssembly(System.Reflection.AssemblyName,System.Reflection.Emit.AssemblyBuilderAccess)Note: This API is now obsolete.

Defines a dynamic assembly using the specified name, access mode, and permission requests.

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

[ObsoleteAttribute("Assembly level declarative security is obsolete and is no longer enforced by the CLR by default.  See http://go.microsoft.com/fwlink/?LinkID=155570 for more information.")]
public AssemblyBuilder DefineDynamicAssembly(
	AssemblyName name,
	AssemblyBuilderAccess access,
	PermissionSet requiredPermissions,
	PermissionSet optionalPermissions,
	PermissionSet refusedPermissions


Type: System.Reflection.AssemblyName

The unique identity of the dynamic assembly.

Type: System.Reflection.Emit.AssemblyBuilderAccess

The mode in which the dynamic assembly will be accessed.

Type: System.Security.PermissionSet

The required permissions request.

Type: System.Security.PermissionSet

The optional permissions request.

Type: System.Security.PermissionSet

The refused permissions request.

Return Value

Type: System.Reflection.Emit.AssemblyBuilder

A dynamic assembly with the specified name and features.

Exception Condition

name is null.


The Name property of name is null.


The Name property of name begins with white space, or contains a forward or backward slash.


The operation is attempted on an unloaded application domain.

The permission requests specified for requiredPermissions, optionalPermissions, and refusedPermissions are not used unless the dynamic assembly has been saved and reloaded into memory. To specify permission requests for a transient assembly that is never saved to disk, use an overload of the DefineDynamicAssembly method that specifies evidence as well as requested permissions, and supply an Evidence object.


During the development of code that emits dynamic assemblies, it is recommended that you use an overload of the DefineDynamicAssembly method that specifies evidence and permissions, supply the evidence you want the dynamic assembly to have, and include SecurityPermissionFlag.SkipVerification in refusedPermissions. Including SkipVerification in the refusedPermissions parameter ensures that the MSIL is verified. A limitation of this technique is that it also causes SecurityException to be thrown when used with code that demands full trust.

This method should only be used to define a dynamic assembly in the current application domain. For more information, see the Load(AssemblyName) method overload .

The following sample demonstrates the DefineDynamicAssembly method and AssemblyResolve event.

For this code example to run, you must provide the fully qualified assembly name. For information about how to obtain the fully qualified assembly name, see Assembly Names.

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

class Test {
   public static void Main() {
      AppDomain currentDomain = AppDomain.CurrentDomain;

      InstantiateMyDynamicType(currentDomain);   // Failed!

      currentDomain.AssemblyResolve += new ResolveEventHandler(MyResolveEventHandler);

      InstantiateMyDynamicType(currentDomain);   // OK!

   static void InstantiateMyDynamicType(AppDomain domain) {
      try {
         // You must supply a valid fully qualified assembly name here. 
         domain.CreateInstance("Assembly text name, Version, Culture, PublicKeyToken", "MyDynamicType");
      } catch (Exception e) {

   static Assembly MyResolveEventHandler(object sender, ResolveEventArgs args) {
      return DefineDynamicAssembly((AppDomain) sender);

   static Assembly DefineDynamicAssembly(AppDomain domain) {
      // Build a dynamic assembly using Reflection Emit API.

      AssemblyName assemblyName = new AssemblyName();
      assemblyName.Name = "MyDynamicAssembly";

      AssemblyBuilder assemblyBuilder = domain.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Run);
      ModuleBuilder moduleBuilder = assemblyBuilder.DefineDynamicModule("MyDynamicModule");
      TypeBuilder typeBuilder = moduleBuilder.DefineType("MyDynamicType", TypeAttributes.Public);
      ConstructorBuilder constructorBuilder = typeBuilder.DefineConstructor(MethodAttributes.Public, CallingConventions.Standard, null);
      ILGenerator ilGenerator = constructorBuilder.GetILGenerator();

      ilGenerator.EmitWriteLine("MyDynamicType instantiated!");


      return assemblyBuilder;

.NET Framework
Available since 1.1
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