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TypeBuilder.CreateType Method

Creates a Type object for the class. After defining fields and methods on the class, CreateType is called in order to load its Type object.

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

Public Function CreateType As Type
Dim instance As TypeBuilder 
Dim returnValue As Type 

returnValue = instance.CreateType()

Return Value

Type: System.Type
Returns the new Type object for this class.


The enclosing type has not been created.


This type is non-abstract and contains an abstract method.


This type is not an abstract class or an interface and has a method without a method body.


The type contains invalid Microsoft intermediate language (MSIL) code.


The branch target is specified using a 1-byte offset, but the target is at a distance greater than 127 bytes from the branch.


The type cannot be loaded. For example, it contains a static method that has the calling convention HasThis.

If this type is a nested type, the CreateType method must be called on the enclosing type before it is called on the nested type.

If the current type derives from an incomplete type or implements incomplete interfaces, call the CreateType method on the parent type and the interface types before calling it on the current type.

If the enclosing type contains a field that is a value type defined as a nested type (for example, a field that is an enumeration defined as a nested type), calling the CreateType method on the enclosing type will generate a AppDomain.TypeResolve event. This is because the loader cannot determine the size of the enclosing type until the nested type has been completed. The caller should define a handler for the TypeResolve event to complete the definition of the nested type by calling CreateType on the TypeBuilder object that represents the nested type. The code example for this topic shows how to define such an event handler.

A type is created only once, no matter how many times the CreateType method is called. All calls return the same Type object.

The following code example shows how to define an event handler for the AppDomain.TypeResolve event, in order to call the CreateType method on a nested type during a CreateType call on the enclosing type.

Imports System
Imports System.Reflection
Imports System.Reflection.Emit
Imports System.Threading
Imports System.Text
Imports System.Resources
Imports System.Collections
Imports System.IO

Friend Class NestedEnum
   Friend Shared enumType As TypeBuilder = Nothing 
   Friend Shared tNested As Type = Nothing 
   Friend Shared tNesting As Type = Nothing 

   Public Shared Sub Main()
      Dim asmName As New AssemblyName()
      asmName.Name = "NestedEnum" 
      Dim asmBuild As AssemblyBuilder = Thread.GetDomain().DefineDynamicAssembly(asmName, AssemblyBuilderAccess.RunAndSave)
      Dim modBuild As ModuleBuilder = asmBuild.DefineDynamicModule("ModuleOne", "NestedEnum.dll")

      ' Hook up the event listening. 
      Dim typeResolveHandler As New TypeResolveHandler(modBuild)
      ' Add a listener for the type resolve events. 
      Dim currentDomain As AppDomain = Thread.GetDomain()
      Dim resolveHandler As ResolveEventHandler = AddressOf typeResolveHandler.ResolveEvent
      AddHandler currentDomain.TypeResolve, resolveHandler 

      Dim tb As TypeBuilder = modBuild.DefineType("AType", TypeAttributes.Public)
      Dim eb As TypeBuilder = tb.DefineNestedType("AnEnum", TypeAttributes.NestedPublic Or TypeAttributes.Sealed, GetType([Enum]))
      eb.DefineField("value__", GetType(Integer), FieldAttributes.Private Or FieldAttributes.SpecialName)
      Dim fb As FieldBuilder = eb.DefineField("Field1", eb, FieldAttributes.Public Or FieldAttributes.Literal Or FieldAttributes.Static)

      enumType = eb

      ' Comment out this field. 
      ' When this field is defined, the loader cannot determine the size 
      ' of the type. Therefore, a TypeResolve event is generated when the 
      ' nested type is completed.
      tb.DefineField("Field2", eb, FieldAttributes.Public)

      tNesting = tb.CreateType()
      If tNesting Is Nothing Then
         Console.WriteLine("NestingType CreateType failed but didn't throw!")
      End If  
         tNested = eb.CreateType()
         If tNested Is Nothing Then
            Console.WriteLine("NestedType CreateType failed but didn't throw!")
         End If 
      End Try ' This is needed because you might have already completed the type in the TypeResolve event.

      If Not (tNested Is Nothing) Then 
         Dim x As Type = tNested.DeclaringType
         If x Is Nothing Then
            Console.WriteLine("Declaring type is Nothing.")
         End If 
      End If 

      ' Remove the listener for the type resolve events. 
      RemoveHandler currentDomain.TypeResolve, resolveHandler 
   End Sub 'Main
End Class 'NestedEnum

' Helper class called when a resolve type event is raised. 
Friend Class TypeResolveHandler
   Private m_Module As [Module]

   Public Sub New([mod] As [Module])
      m_Module = [mod]
   End Sub 'New 

   Public Function ResolveEvent(sender As [Object], args As ResolveEventArgs) As [Assembly]
      ' Use args.Name to look up the type name. In this case, you are getting AnEnum. 
         NestedEnum.tNested = NestedEnum.enumType.CreateType()
      End Try ' This is needed to throw away InvalidOperationException.
      ' Loader might send the TypeResolve event more than once 
      ' and the type might be complete already. 

      ' Complete the type.		     
      Return m_Module.Assembly
   End Function 'ResolveEvent
End Class 'TypeResolveHandler

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0