TypeBuilder.DefineProperty Method (String, PropertyAttributes, Type, array<Type[])
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Adds a new property to the type, with the given name and property signature.
Namespace: System.Reflection.Emit
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Function DefineProperty ( _
name As String, _
attributes As PropertyAttributes, _
returnType As Type, _
parameterTypes As Type() _
) As PropertyBuilder
public PropertyBuilder DefineProperty(
string name,
PropertyAttributes attributes,
Type returnType,
Type[] parameterTypes
)
Parameters
- name
Type: System.String
The name of the property. name cannot contain embedded nulls.
- attributes
Type: System.Reflection.PropertyAttributes
The attributes of the property.
- returnType
Type: System.Type
The return type of the property.
- parameterTypes
Type: array<System.Type[]
The types of the parameters of the property.
Return Value
Type: System.Reflection.Emit.PropertyBuilder
The defined property.
Exceptions
| Exception | Condition |
|---|---|
| ArgumentException | The length of name is zero. |
| ArgumentNullException | name is nulla null reference (Nothing in Visual Basic). -or- Any of the elements of the parameterTypes array is nulla null reference (Nothing in Visual Basic). |
| InvalidOperationException | The type was previously created using CreateType. |
Examples
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.
.gif "Note") Note: |
|---|
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control. |
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
using System;
using System.Reflection;
using System.Reflection.Emit;
class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
// 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. In C# the type might look like this:
/*
public class MyDynamicType
{
private int m_number;
public MyDynamicType() : this(42) {}
public MyDynamicType(int initNumber)
{
m_number = initNumber;
}
public int Number
{
get { return m_number; }
set { m_number = value; }
}
public int MyMethod(int multiplier)
{
return m_number * multiplier;
}
}
*/
AssemblyName aName = new AssemblyName("DynamicAssemblyExample");
AssemblyBuilder ab =
AppDomain.CurrentDomain.DefineDynamicAssembly(
aName,
AssemblyBuilderAccess.Run);
// Create the module.
ModuleBuilder mb = ab.DefineDynamicModule(aName.Name);
TypeBuilder tb = mb.DefineType(
"MyDynamicType",
TypeAttributes.Public);
// Add a private field of type int (Int32).
FieldBuilder fbNumber = tb.DefineField(
"m_number",
typeof(int),
FieldAttributes.Private);
// Define a constructor that takes an integer argument and
// stores it in the private field.
Type[] parameterTypes = { typeof(int) };
ConstructorBuilder ctor1 = tb.DefineConstructor(
MethodAttributes.Public,
CallingConventions.Standard,
parameterTypes);
ILGenerator ctor1IL = 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,
typeof(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 null.
ConstructorBuilder ctor0 = tb.DefineConstructor(
MethodAttributes.Public,
CallingConventions.Standard,
Type.EmptyTypes);
ILGenerator ctor0IL = 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 null, because the
// property has no parameters. (If you don't specify null, you must
// specify an array of Type objects. For a parameterless property,
// use the built-in array with no elements: Type.EmptyTypes)
PropertyBuilder pbNumber = tb.DefineProperty(
"Number",
PropertyAttributes.HasDefault,
typeof(int),
null);
// The property "set" and property "get" methods require a special
// set of attributes.
MethodAttributes getSetAttr = MethodAttributes.Public |
MethodAttributes.SpecialName | MethodAttributes.HideBySig;
// Define the "get" accessor method for Number. The method returns
// an integer and has no arguments. (Note that null could be
// used instead of Types.EmptyTypes)
MethodBuilder mbNumberGetAccessor = tb.DefineMethod(
"get_Number",
getSetAttr,
typeof(int),
Type.EmptyTypes);
ILGenerator numberGetIL = 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 int (Int32).
MethodBuilder mbNumberSetAccessor = tb.DefineMethod(
"set_Number",
getSetAttr,
null,
new Type[] { typeof(int) });
ILGenerator numberSetIL = 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.
MethodBuilder meth = tb.DefineMethod(
"MyMethod",
MethodAttributes.Public,
typeof(int),
new Type[] { typeof(int) });
ILGenerator methIL = 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.
Type t = tb.CreateType();
// The code can be executed immediately. Start by getting reflection
// objects for the method and the property.
MethodInfo mi = t.GetMethod("MyMethod");
PropertyInfo pi = t.GetProperty("Number");
// Create an instance of MyDynamicType using the default
// constructor.
object o1 = Activator.CreateInstance(t);
// Display the value of the property, then change it to 127 and
// display it again. Use null to indicate that the property
// has no index.
outputBlock.Text += String.Format("o1.Number: {0}\n", pi.GetValue(o1, null));
pi.SetValue(o1, 127, null);
outputBlock.Text += String.Format("o1.Number: {0}\n", pi.GetValue(o1, null));
// 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.
object[] arguments = { 22 };
outputBlock.Text += String.Format("o1.MyMethod(22): {0}\n",
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.
object o2 = Activator.CreateInstance(t,
new object[] { 5280 });
outputBlock.Text += String.Format("o2.Number: {0}\n", pi.GetValue(o2, null));
}
}
/* This code produces the following output:
o1.Number: 42
o1.Number: 127
o1.MyMethod(22): 2794
o2.Number: 5280
*/
Version Information
Silverlight
Supported in: 5, 4, 3
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.