AppDomain.CurrentDomain Property

Gets the current application domain for the current Thread.

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

'Declaration
Public Shared ReadOnly Property CurrentDomain As AppDomain

Property Value

Type: System.AppDomain
The current application domain.

The following example shows how to use the CurrentDomain property when you create a dynamic assembly in the current application domain.


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, _
              AssemblyBuilderAccess.Run)

      ' 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), _
          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 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


Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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