TypeBuilder.DefineMethod Method (String, MethodAttributes, Type, Type())

Adds a new method to the type, with the specified name, method attributes, and method signature.

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

Public Function DefineMethod ( _
	name As String, _
	attributes As MethodAttributes, _
	returnType As Type, _
	parameterTypes As Type() _
) As MethodBuilder


Type: System.String
The name of the method. name cannot contain embedded nulls.
Type: System.Reflection.MethodAttributes
The attributes of the method.
Type: System.Type
The return type of the method.
Type: System.Type()
The types of the parameters of the method.

Return Value

Type: System.Reflection.Emit.MethodBuilder
The defined method.


The length of name is zero.


The type of the parent of this method is an interface, and this method is not virtual (Overridable in Visual Basic).


name is Nothing.


The type was previously created using CreateType.


For the current dynamic type, the IsGenericType property is true, but the IsGenericTypeDefinition property is false.

The following 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.

Imports System.Reflection
Imports System.Reflection.Emit

Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      ' In this version of the runtime, an assembly consists of one 
      ' module which contains zero or more types. This example 
      ' creates an assembly containing one public type named
      ' "MyDynamicType". The type 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

      Dim aName As New AssemblyName("DynamicAssemblyExample")
      Dim ab As AssemblyBuilder = _
          AppDomain.CurrentDomain.DefineDynamicAssembly( _
              aName, _

      ' Create the module.
      Dim mb As ModuleBuilder = ab.DefineDynamicModule(aName.Name)

      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), _

      ' 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, _

      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.Call, _
      ' Push the instance on the stack before pushing the argument
      ' that is to be assigned to the private field m_number.
      ctor1IL.Emit(OpCodes.Stfld, fbNumber)

      ' 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, _

      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.Ldc_I4_S, 42)
      ctor0IL.Emit(OpCodes.Call, ctor1)

      ' 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), _

      ' 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), _

      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.Ldfld, fbNumber)

      ' 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.Stfld, fbNumber)

      ' Last, map the "get" and "set" accessor methods to the 
      ' PropertyBuilder. The property is now complete. 

      ' 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.Ldfld, fbNumber)

      ' Finish the type.
      Dim t As Type = tb.CreateType()

      ' 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.
      outputBlock.Text += String.Format("o1.Number: {0}" & vbCrLf, _
          pi.GetValue(o1, Nothing)) 
      pi.SetValue(o1, 127, Nothing)
      outputBlock.Text += String.Format("o1.Number: {0}" & vbCrLf, _
          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}
      outputBlock.Text &= String.Format("o1.MyMethod(22): {0}" & vbCrLf, _
          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})
      outputBlock.Text += String.Format("o2.Number: {0}" & vbCrLf, _
          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


Supported in: 5, 4, 3

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