AssemblyBuilder Class
Defines and represents a dynamic assembly.
Assembly: mscorlib (in mscorlib.dll)
'Declaration <ComVisibleAttribute(True)> _ <ClassInterfaceAttribute(ClassInterfaceType.None)> _ <HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort := True)> _ Public NotInheritable Class AssemblyBuilder _ Inherits Assembly _ Implements _AssemblyBuilder 'Usage Dim instance As AssemblyBuilder
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The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: MayLeakOnAbort. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes. |
A dynamic assembly is an assembly that is created using the Reflection Emit APIs. The dynamic modules in the assembly are saved when the dynamic assembly is saved using the Save method. To generate an executable, the SetEntryPoint method must be called to identify the method that is the entry point to the assembly. Assemblies are saved as DLL by default, unless SetEntryPoint requests the generation of a console application or a Windows-based application.
If a dynamic assembly contains more than one dynamic module, the assembly's manifest file name should match the module's name that is specified as the first argument to DefineDynamicModule.
Some methods on the base class Assembly such as GetModules and GetLoadedModules will not work correctly when called AssemblyBuilder objects. You can load the defined dynamic assembly and call the methods on the loaded assembly. For example, to ensure that resource modules are included in the returned module list, call GetModules on the loaded Assembly object.
The signing of a dynamic assembly using KeyPair is not effective until the assembly is saved to disk. So, strong names will not work with transient dynamic assemblies.
To get an AssemblyBuilder object, use the AppDomain.DefineDynamicAssembly method.
The following code example shows how to define a dynamic assembly with one module. The module in the example assembly contains one type, MyDynamicType, which has a private field, a property that gets and sets the private field, constructors that initialize the private field, and a method that multiplies a user-supplied number by the private field value and returns the result.
AssemblyBuilderAccess.RunAndSave is specified when the assembly is created. The assembly code is used immediately, and the assembly is also saved to disk so that it can be examined with MSIL Disassembler (Ildasm.exe) or used in another program.
Imports System Imports System.Reflection Imports System.Reflection.Emit Class DemoAssemblyBuilder Public Shared Sub Main() ' An assembly consists of one or more modules, each of which ' contains zero or more types. This code creates a single-module ' assembly, the most common case. The module contains one type, ' named "MyDynamicType", that has a private field, a property ' that gets and sets the private field, constructors that ' initialize the private field, and a method that multiplies ' a user-supplied number by the private field value and returns ' the result. The code might look like this in Visual Basic: ' 'Public Class MyDynamicType ' Private m_number As Integer ' ' Public Sub New() ' Me.New(42) ' End Sub ' ' Public Sub New(ByVal initNumber As Integer) ' m_number = initNumber ' End Sub ' ' Public Property Number As Integer ' Get ' Return m_number ' End Get ' Set ' m_Number = Value ' End Set ' End Property ' ' Public Function MyMethod(ByVal multiplier As Integer) As Integer ' Return m_Number * multiplier ' End Function 'End Class Dim aName As New AssemblyName("DynamicAssemblyExample") Dim ab As AssemblyBuilder = _ AppDomain.CurrentDomain.DefineDynamicAssembly( _ aName, _ AssemblyBuilderAccess.RunAndSave) ' For a single-module assembly, the module name is usually ' the assembly name plus an extension. Dim mb As ModuleBuilder = ab.DefineDynamicModule( _ aName.Name, _ aName.Name & ".dll") Dim tb As TypeBuilder = _ mb.DefineType("MyDynamicType", TypeAttributes.Public) ' Add a private field of type Integer (Int32). Dim fbNumber As FieldBuilder = tb.DefineField( _ "m_number", _ GetType(Integer), _ FieldAttributes.Private) ' Define a constructor that takes an integer argument and ' stores it in the private field. Dim parameterTypes() As Type = { GetType(Integer) } Dim ctor1 As ConstructorBuilder = _ tb.DefineConstructor( _ MethodAttributes.Public, _ CallingConventions.Standard, _ parameterTypes) Dim ctor1IL As ILGenerator = ctor1.GetILGenerator() ' For a constructor, argument zero is a reference to the new ' instance. Push it on the stack before calling the base ' class constructor. Specify the default constructor of the ' base class (System.Object) by passing an empty array of ' types (Type.EmptyTypes) to GetConstructor. ctor1IL.Emit(OpCodes.Ldarg_0) ctor1IL.Emit(OpCodes.Call, _ GetType(Object).GetConstructor(Type.EmptyTypes)) ' Push the instance on the stack before pushing the argument ' that is to be assigned to the private field m_number. ctor1IL.Emit(OpCodes.Ldarg_0) ctor1IL.Emit(OpCodes.Ldarg_1) ctor1IL.Emit(OpCodes.Stfld, fbNumber) ctor1IL.Emit(OpCodes.Ret) ' Define a default constructor that supplies a default value ' for the private field. For parameter types, pass the empty ' array of types or pass Nothing. Dim ctor0 As ConstructorBuilder = tb.DefineConstructor( _ MethodAttributes.Public, _ CallingConventions.Standard, _ Type.EmptyTypes) Dim ctor0IL As ILGenerator = ctor0.GetILGenerator() ' For a constructor, argument zero is a reference to the new ' instance. Push it on the stack before pushing the default ' value on the stack, then call constructor ctor1. ctor0IL.Emit(OpCodes.Ldarg_0) ctor0IL.Emit(OpCodes.Ldc_I4_S, 42) ctor0IL.Emit(OpCodes.Call, ctor1) ctor0IL.Emit(OpCodes.Ret) ' Define a property named Number that gets and sets the private ' field. ' ' The last argument of DefineProperty is Nothing, because the ' property has no parameters. (If you don't specify Nothing, you must ' specify an array of Type objects. For a parameterless property, ' use the built-in array with no elements: Type.EmptyTypes) Dim pbNumber As PropertyBuilder = tb.DefineProperty( _ "Number", _ PropertyAttributes.HasDefault, _ GetType(Integer), _ Nothing) ' The property Set and property Get methods require a special ' set of attributes. Dim getSetAttr As MethodAttributes = _ MethodAttributes.Public Or MethodAttributes.SpecialName _ Or MethodAttributes.HideBySig ' Define the "get" accessor method for Number. The method returns ' an integer and has no arguments. (Note that Nothing could be ' used instead of Types.EmptyTypes) Dim mbNumberGetAccessor As MethodBuilder = tb.DefineMethod( _ "get_Number", _ getSetAttr, _ GetType(Integer), _ Type.EmptyTypes) Dim numberGetIL As ILGenerator = mbNumberGetAccessor.GetILGenerator() ' For an instance property, argument zero is the instance. Load the ' instance, then load the private field and return, leaving the ' field value on the stack. numberGetIL.Emit(OpCodes.Ldarg_0) numberGetIL.Emit(OpCodes.Ldfld, fbNumber) numberGetIL.Emit(OpCodes.Ret) ' Define the "set" accessor method for Number, which has no return ' type and takes one argument of type Integer (Int32). Dim mbNumberSetAccessor As MethodBuilder = _ tb.DefineMethod( _ "set_Number", _ getSetAttr, _ Nothing, _ New Type() { GetType(Integer) }) Dim numberSetIL As ILGenerator = mbNumberSetAccessor.GetILGenerator() ' Load the instance and then the numeric argument, then store the ' argument in the field. numberSetIL.Emit(OpCodes.Ldarg_0) numberSetIL.Emit(OpCodes.Ldarg_1) numberSetIL.Emit(OpCodes.Stfld, fbNumber) numberSetIL.Emit(OpCodes.Ret) ' Last, map the "get" and "set" accessor methods to the ' PropertyBuilder. The property is now complete. pbNumber.SetGetMethod(mbNumberGetAccessor) pbNumber.SetSetMethod(mbNumberSetAccessor) ' Define a method that accepts an integer argument and returns ' the product of that integer and the private field m_number. This ' time, the array of parameter types is created on the fly. Dim meth As MethodBuilder = tb.DefineMethod( _ "MyMethod", _ MethodAttributes.Public, _ GetType(Integer), _ New Type() { GetType(Integer) }) Dim methIL As ILGenerator = meth.GetILGenerator() ' To retrieve the private instance field, load the instance it ' belongs to (argument zero). After loading the field, load the ' argument one and then multiply. Return from the method with ' the return value (the product of the two numbers) on the ' execution stack. methIL.Emit(OpCodes.Ldarg_0) methIL.Emit(OpCodes.Ldfld, fbNumber) methIL.Emit(OpCodes.Ldarg_1) methIL.Emit(OpCodes.Mul) methIL.Emit(OpCodes.Ret) ' Finish the type. Dim t As Type = tb.CreateType() ' The following line saves the single-module assembly. This ' requires AssemblyBuilderAccess to include Save. You can now ' type "ildasm MyDynamicAsm.dll" at the command prompt, and ' examine the assembly. You can also write a program that has ' a reference to the assembly, and use the MyDynamicType type. ' ab.Save(aName.Name & ".dll") ' Because AssemblyBuilderAccess includes Run, the code can be ' executed immediately. Start by getting reflection objects for ' the method and the property. Dim mi As MethodInfo = t.GetMethod("MyMethod") Dim pi As PropertyInfo = t.GetProperty("Number") ' Create an instance of MyDynamicType using the default ' constructor. Dim o1 As Object = Activator.CreateInstance(t) ' Display the value of the property, then change it to 127 and ' display it again. Use Nothing to indicate that the property ' has no index. Console.WriteLine("o1.Number: {0}", pi.GetValue(o1, Nothing)) pi.SetValue(o1, 127, Nothing) Console.WriteLine("o1.Number: {0}", pi.GetValue(o1, Nothing)) ' Call MyMethod, passing 22, and display the return value, 22 ' times 127. Arguments must be passed as an array, even when ' there is only one. Dim arguments() As Object = { 22 } Console.WriteLine("o1.MyMethod(22): {0}", _ mi.Invoke(o1, arguments)) ' Create an instance of MyDynamicType using the constructor ' that specifies m_Number. The constructor is identified by ' matching the types in the argument array. In this case, ' the argument array is created on the fly. Display the ' property value. Dim o2 As Object = Activator.CreateInstance(t, _ New Object() { 5280 }) Console.WriteLine("o2.Number: {0}", pi.GetValue(o2, Nothing)) End Sub End Class ' This code produces the following output: ' 'o1.Number: 42 'o1.Number: 127 'o1.MyMethod(22): 2794 'o2.Number: 5280
- ReflectionPermission
when invoked late-bound through mechanisms such as Type.InvokeMember. Associated enumeration: ReflectionPermissionFlag.MemberAccess.
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.
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