Procedimiento para definir y ejecutar métodos dinámicosHow to: Define and Execute Dynamic Methods

En los procedimientos siguientes se muestra cómo definir y ejecutar un método dinámico simple y un método dinámico enlazado a una instancia de una clase.The following procedures show how to define and execute a simple dynamic method and a dynamic method bound to an instance of a class. Para obtener más información sobre los métodos dinámicos, vea la clase DynamicMethod y Reflection Emit Dynamic Method Scenarios (Escenarios de métodos dinámicos de emisión de reflexión).For more information on dynamic methods, see the DynamicMethod class and Reflection Emit Dynamic Method Scenarios.

Para definir y ejecutar un método dinámicoTo define and execute a dynamic method

  1. Declare un tipo delegado para ejecutar el método.Declare a delegate type to execute the method. Considere la posibilidad de usar un delegado genérico para minimizar el número de tipos delegados que necesita declarar.Consider using a generic delegate to minimize the number of delegate types you need to declare. El código siguiente declara dos tipos delegados que podrían usarse para el método SquareIt, y uno de ellos es genérico.The following code declares two delegate types that could be used for the SquareIt method, and one of them is generic.

    private: 
        delegate long long SquareItInvoker(int input);
    
        generic<typename TReturn, typename TParameter0> 
            delegate TReturn OneParameter(TParameter0 p0);
    
    private delegate long SquareItInvoker(int input);
    
    private delegate TReturn OneParameter<TReturn, TParameter0>
        (TParameter0 p0);
    
    Private Delegate Function _
        SquareItInvoker(ByVal input As Integer) As Long
    
    Private Delegate Function _
        OneParameter(Of TReturn, TParameter0) _
        (ByVal p0 As TParameter0) As TReturn
    
  2. Cree una matriz que especifique los tipos de parámetro para el método dinámico.Create an array that specifies the parameter types for the dynamic method. En este ejemplo, el único parámetro es int (Integer en Visual Basic), por lo que la matriz solo tiene un elemento.In this example, the only parameter is an int (Integer in Visual Basic), so the array has only one element.

    array<Type^>^ methodArgs = { int::typeid };
    
    Type[] methodArgs = {typeof(int)};
    
    Dim methodArgs As Type() = {GetType(Integer)}
    
  3. Creará un control DynamicMethod.Create a DynamicMethod. En este ejemplo, el método se denomina SquareIt.In this example the method is named SquareIt.

    Nota

    No es necesario asignar un nombre a los métodos dinámicos, y estos no se pueden invocar por su nombre.It is not necessary to give dynamic methods names, and they cannot be invoked by name. Se admite que varios métodos dinámicos tengan el mismo nombre,Multiple dynamic methods can have the same name. pero el nombre aparece en pilas de llamadas y puede ser útil para la depuración.However, the name appears in call stacks and can be useful for debugging.

    El tipo del valor devuelto se especifica como long.The type of the return value is specified as long. El método está asociado con el módulo que contiene la clase Example, que contiene el código de ejemplo.The method is associated with the module that contains the Example class, which contains the example code. Se puede especificar cualquier módulo cargado.Any loaded module could be specified. El método dinámico actúa como un método static de nivel de módulo (Shared en Visual Basic).The dynamic method acts like a module-level static method (Shared in Visual Basic).

    DynamicMethod^ squareIt = gcnew DynamicMethod(
        "SquareIt", 
        long long::typeid, 
        methodArgs, 
        Example::typeid->Module);
    
    DynamicMethod squareIt = new DynamicMethod(
        "SquareIt",
        typeof(long),
        methodArgs,
        typeof(Example).Module);
    
    Dim squareIt As New DynamicMethod( _
        "SquareIt", _
        GetType(Long), _
        methodArgs, _
        GetType(Example).Module)
    
  4. Emita el cuerpo del método.Emit the method body. En este ejemplo, se usa un objeto ILGenerator para emitir el Lenguaje Intermedio de Microsoft (MSIL).In this example, an ILGenerator object is used to emit the Microsoft intermediate language (MSIL). Como alternativa, se puede usar un objeto DynamicILInfo junto con generadores de código no administrado para emitir el cuerpo del método para un DynamicMethod.Alternatively, a DynamicILInfo object can be used in conjunction with unmanaged code generators to emit the method body for a DynamicMethod.

    En este ejemplo, MSIL carga el argumento (que es int) en la pila, lo convierte en long, duplica long y multiplica los dos números.The MSIL in this example loads the argument, which is an int, onto the stack, converts it to a long, duplicates the long, and multiplies the two numbers. Esto deja el resultado al cuadrado en la pila, y lo único que tiene que hacer el método es devolverlo.This leaves the squared result on the stack, and all the method has to do is return.

    ILGenerator^ il = squareIt->GetILGenerator();
    il->Emit(OpCodes::Ldarg_0);
    il->Emit(OpCodes::Conv_I8);
    il->Emit(OpCodes::Dup);
    il->Emit(OpCodes::Mul);
    il->Emit(OpCodes::Ret);
    
    ILGenerator il = squareIt.GetILGenerator();
    il.Emit(OpCodes.Ldarg_0);
    il.Emit(OpCodes.Conv_I8);
    il.Emit(OpCodes.Dup);
    il.Emit(OpCodes.Mul);
    il.Emit(OpCodes.Ret);
    
    Dim il As ILGenerator = squareIt.GetILGenerator()
    il.Emit(OpCodes.Ldarg_0)
    il.Emit(OpCodes.Conv_I8)
    il.Emit(OpCodes.Dup)
    il.Emit(OpCodes.Mul)
    il.Emit(OpCodes.Ret)
    
  5. Llame al método CreateDelegate para crear una instancia del delegado (declarado en el paso 1) que represente el método dinámico.Create an instance of the delegate (declared in step 1) that represents the dynamic method by calling the CreateDelegate method. La creación del delegado finaliza el método y todos los intentos posteriores de cambiar el método (por ejemplo, mediante la adición de MSIL) se omiten.Creating the delegate completes the method, and any further attempts to change the method — for example, adding more MSIL — are ignored. El código siguiente crea el delegado y lo invoca mediante un delegado genérico.The following code creates the delegate and invokes it, using a generic delegate.

    OneParameter<long long, int>^ invokeSquareIt = 
        (OneParameter<long long, int>^)
        squareIt->CreateDelegate(OneParameter<long long, int>::typeid);
    
    Console::WriteLine("123456789 squared = {0}",
        invokeSquareIt(123456789));
    
    OneParameter<long, int> invokeSquareIt =
        (OneParameter<long, int>)
        squareIt.CreateDelegate(typeof(OneParameter<long, int>));
    
    Console.WriteLine("123456789 squared = {0}",
        invokeSquareIt(123456789));
    
    Dim invokeSquareIt As OneParameter(Of Long, Integer) = _
        CType( _
            squareIt.CreateDelegate( _
                GetType(OneParameter(Of Long, Integer))), _
            OneParameter(Of Long, Integer) _
        )
    
    Console.WriteLine("123456789 squared = {0}", _
        invokeSquareIt(123456789))
    

Para definir y ejecutar un método dinámico enlazado a un objetoTo define and execute a dynamic method that is bound to an object

  1. Declare un tipo delegado para ejecutar el método.Declare a delegate type to execute the method. Considere la posibilidad de usar un delegado genérico para minimizar el número de tipos delegados que necesita declarar.Consider using a generic delegate to minimize the number of delegate types you need to declare. El código siguiente declara un tipo delegado genérico que puede usarse para ejecutar cualquier método con un parámetro y un valor devuelto, o un método con dos parámetros y un valor devuelto si el delegado está enlazado a un objeto.The following code declares a generic delegate type that can be used to execute any method with one parameter and a return value, or a method with two parameters and a return value if the delegate is bound to an object.

    generic<typename TReturn, typename TParameter0> 
        delegate TReturn OneParameter(TParameter0 p0);
    
    private delegate TReturn OneParameter<TReturn, TParameter0>
        (TParameter0 p0);
    
    Private Delegate Function _
        OneParameter(Of TReturn, TParameter0) _
        (ByVal p0 As TParameter0) As TReturn
    
  2. Cree una matriz que especifique los tipos de parámetro para el método dinámico.Create an array that specifies the parameter types for the dynamic method. Si el delegado que representa el método va a enlazarse a un objeto, el primer parámetro debe coincidir con el tipo al que se enlaza el delegado.If the delegate representing the method is to be bound to an object, the first parameter must match the type the delegate is bound to. En este ejemplo, hay dos parámetros, de tipo Example y tipo int (Integer en Visual Basic).In this example, there are two parameters, of type Example and type int (Integer in Visual Basic).

    array<Type^>^ methodArgs2 = { Example::typeid, int::typeid };
    
    Type[] methodArgs2 = { typeof(Example), typeof(int) };
    
    Dim methodArgs2 As Type() = _
        {GetType(Example), GetType(Integer)}
    
  3. Creará un control DynamicMethod.Create a DynamicMethod. En este ejemplo el método no tiene nombre.In this example the method has no name. El tipo del valor devuelto se especifica como int (Integer in Visual Basic).The type of the return value is specified as int (Integer in Visual Basic). El método tiene acceso a los miembros privados y protegidos de la clase Example.The method has access to the private and protected members of the Example class.

    DynamicMethod^ multiplyHidden = gcnew DynamicMethod(
        "", 
        int::typeid, 
        methodArgs2, 
        Example::typeid);
    
    DynamicMethod multiplyHidden = new DynamicMethod(
        "",
        typeof(int),
        methodArgs2,
        typeof(Example));
    
    Dim multiplyPrivate As New DynamicMethod( _
        "", _
        GetType(Integer), _
        methodArgs2, _
        GetType(Example))
    
  4. Emita el cuerpo del método.Emit the method body. En este ejemplo, se usa un objeto ILGenerator para emitir el Lenguaje Intermedio de Microsoft (MSIL).In this example, an ILGenerator object is used to emit the Microsoft intermediate language (MSIL). Como alternativa, se puede usar un objeto DynamicILInfo junto con generadores de código no administrado para emitir el cuerpo del método para un DynamicMethod.Alternatively, a DynamicILInfo object can be used in conjunction with unmanaged code generators to emit the method body for a DynamicMethod.

    En este ejemplo, MSIL carga el primer argumento, que es una instancia de la clase Example, y lo usa para cargar el valor de un campo de instancia privada de tipo int.The MSIL in this example loads the first argument, which is an instance of the Example class, and uses it to load the value of a private instance field of type int. Se carga el segundo argumento y se multiplican los dos números.The second argument is loaded, and the two numbers are multiplied. Si el resultado es mayor que int, el valor se trunca y se descartan los bits más significativos.If the result is larger than int, the value is truncated and the most significant bits are discarded. El método devuelve un valor, con el valor devuelto en la pila.The method returns, with the return value on the stack.

    ILGenerator^ ilMH = multiplyHidden->GetILGenerator();
    ilMH->Emit(OpCodes::Ldarg_0);
    
    FieldInfo^ testInfo = Example::typeid->GetField("test",
        BindingFlags::NonPublic | BindingFlags::Instance);
    
    ilMH->Emit(OpCodes::Ldfld, testInfo);
    ilMH->Emit(OpCodes::Ldarg_1);
    ilMH->Emit(OpCodes::Mul);
    ilMH->Emit(OpCodes::Ret);
    
    ILGenerator ilMH = multiplyHidden.GetILGenerator();
    ilMH.Emit(OpCodes.Ldarg_0);
    
    FieldInfo testInfo = typeof(Example).GetField("test",
        BindingFlags.NonPublic | BindingFlags.Instance);
    
    ilMH.Emit(OpCodes.Ldfld, testInfo);
    ilMH.Emit(OpCodes.Ldarg_1);
    ilMH.Emit(OpCodes.Mul);
    ilMH.Emit(OpCodes.Ret);
    
    Dim ilMP As ILGenerator = multiplyPrivate.GetILGenerator()
    ilMP.Emit(OpCodes.Ldarg_0)
    
    Dim testInfo As FieldInfo = _
        GetType(Example).GetField("test", _
            BindingFlags.NonPublic Or BindingFlags.Instance)
    
    ilMP.Emit(OpCodes.Ldfld, testInfo)
    ilMP.Emit(OpCodes.Ldarg_1)
    ilMP.Emit(OpCodes.Mul)
    ilMP.Emit(OpCodes.Ret)
    
  5. Cree una instancia del delegado (declarado en el paso 1) que represente el método dinámico mediante una llamada a la sobrecarga del método CreateDelegate(Type, Object).Create an instance of the delegate (declared in step 1) that represents the dynamic method by calling the CreateDelegate(Type, Object) method overload. La creación del delegado finaliza el método y todos los intentos posteriores de cambiar el método (por ejemplo, mediante la adición de MSIL) se omiten.Creating the delegate completes the method, and any further attempts to change the method — for example, adding more MSIL — are ignored.

    Nota

    Puede llamar al método CreateDelegate varias veces para crear delegados enlazados a otras instancias del tipo de destino.You can call the CreateDelegate method multiple times to create delegates bound to other instances of the target type.

    El código siguiente enlaza el método a una nueva instancia de la clase Example cuyo campo de prueba privado está establecido en 42.The following code binds the method to a new instance of the Example class whose private test field is set to 42. Es decir, cada vez que se invoca el delegado, la instancia de Example se pasa al primer parámetro del método.That is, each time the delegate is invoked the instance of Example is passed to the first parameter of the method.

    Se usa el delegado OneParameter porque el primer parámetro del método siempre recibe la instancia de Example.The delegate OneParameter is used because the first parameter of the method always receives the instance of Example. Cuando se invoca el delegado, solo es necesario el segundo parámetro.When the delegate is invoked, only the second parameter is required.

    OneParameter<int, int>^ invoke = (OneParameter<int, int>^)
        multiplyHidden->CreateDelegate(
            OneParameter<int, int>::typeid, 
            gcnew Example(42)
        );
    
    Console::WriteLine("3 * test = {0}", invoke(3));
    
    OneParameter<int, int> invoke = (OneParameter<int, int>)
        multiplyHidden.CreateDelegate(
            typeof(OneParameter<int, int>),
            new Example(42)
        );
    
    Console.WriteLine("3 * test = {0}", invoke(3));
    
    Dim invoke As OneParameter(Of Integer, Integer) = _
        CType( _
            multiplyPrivate.CreateDelegate( _
                GetType(OneParameter(Of Integer, Integer)), _
                new Example(42) _
            ), _
            OneParameter(Of Integer, Integer) _
        )
    
    Console.WriteLine("3 * test = {0}", invoke(3))
    

EjemploExample

En el código siguiente se muestra un método dinámico simple y un método dinámico enlazado a una instancia de una clase.The following code example demonstrates a simple dynamic method and a dynamic method bound to an instance of a class.

El método dinámico simple toma un argumento, un entero de 32 bits, y devuelve el cuadrado de 64 bits de ese entero.The simple dynamic method takes one argument, a 32-bit integer, and returns the 64-bit square of that integer. Se usa un delegado genérico para invocar el método.A generic delegate is used to invoke the method.

El segundo método dinámico tiene dos parámetros, de tipo Example y tipo int (Integer en Visual Basic).The second dynamic method has two parameters, of type Example and type int (Integer in Visual Basic). Cuando se ha creado el método dinámico, se enlaza a una instancia de Example mediante un delegado genérico que tiene un argumento de tipo int.When the dynamic method has been created, it is bound to an instance of Example, using a generic delegate that has one argument of type int. El delegado no tiene un argumento de tipo Example porque el primer parámetro del método siempre recibe la instancia enlazada de Example.The delegate does not have an argument of type Example because the first parameter of the method always receives the bound instance of Example. Cuando se invoca el delegado, solo se proporciona el argumento int.When the delegate is invoked, only the int argument is supplied. Este método dinámico obtiene acceso a un campo privado de la clase Example y devuelve el producto del campo privado y el argumento int.This dynamic method accesses a private field of the Example class and returns the product of the private field and the int argument.

En el ejemplo de código se definen delegados que pueden usarse para ejecutar los métodos.The code example defines delegates that can be used to execute the methods.

using namespace System;
using namespace System::Reflection;
using namespace System::Reflection::Emit;

public ref class Example
{
    // The following constructor and private field are used to
    // demonstrate a method bound to an object.
private:
    int test;
    
public:
    Example(int test) { this->test = test; }

    // Declare delegates that can be used to execute the completed 
    // SquareIt dynamic method. The OneParameter delegate can be 
    // used to execute any method with one parameter and a return
    // value, or a method with two parameters and a return value
    // if the delegate is bound to an object.
    //
private: 
    delegate long long SquareItInvoker(int input);

    generic<typename TReturn, typename TParameter0> 
        delegate TReturn OneParameter(TParameter0 p0);

public:
    static void Main()
    {
        // Example 1: A simple dynamic method.
        //
        // Create an array that specifies the parameter types for the
        // dynamic method. In this example the only parameter is an 
        // int, so the array has only one element.
        //
        array<Type^>^ methodArgs = { int::typeid };

        // Create a DynamicMethod. In this example the method is
        // named SquareIt. It is not necessary to give dynamic 
        // methods names. They cannot be invoked by name, and two
        // dynamic methods can have the same name. However, the 
        // name appears in calls stacks and can be useful for
        // debugging. 
        //
        // In this example the return type of the dynamic method is
        // long long. The method is associated with the module that 
        // contains the Example class. Any loaded module could be
        // specified. The dynamic method is like a module-level
        // static method.
        //
        DynamicMethod^ squareIt = gcnew DynamicMethod(
            "SquareIt", 
            long long::typeid, 
            methodArgs, 
            Example::typeid->Module);

        // Emit the method body. In this example ILGenerator is used
        // to emit the MSIL. DynamicMethod has an associated type
        // DynamicILInfo that can be used in conjunction with 
        // unmanaged code generators.
        //
        // The MSIL loads the argument, which is an int, onto the 
        // stack, converts the int to a long long, duplicates the top
        // item on the stack, and multiplies the top two items on the
        // stack. This leaves the squared number on the stack, and 
        // all the method has to do is return.
        //
        ILGenerator^ il = squareIt->GetILGenerator();
        il->Emit(OpCodes::Ldarg_0);
        il->Emit(OpCodes::Conv_I8);
        il->Emit(OpCodes::Dup);
        il->Emit(OpCodes::Mul);
        il->Emit(OpCodes::Ret);

        // Create a delegate that represents the dynamic method. 
        // Creating the delegate completes the method, and any further 
        // attempts to change the method (for example, by adding more
        // MSIL) are ignored. The following code uses a generic 
        // delegate that can produce delegate types matching any
        // single-parameter method that has a return type.
        //
        OneParameter<long long, int>^ invokeSquareIt = 
            (OneParameter<long long, int>^)
            squareIt->CreateDelegate(OneParameter<long long, int>::typeid);

        Console::WriteLine("123456789 squared = {0}",
            invokeSquareIt(123456789));

        // Example 2: A dynamic method bound to an instance.
        //
        // Create an array that specifies the parameter types for a
        // dynamic method. If the delegate representing the method
        // is to be bound to an object, the first parameter must 
        // match the type the delegate is bound to. In the following
        // code the bound instance is of the Example class. 
        //
        array<Type^>^ methodArgs2 = { Example::typeid, int::typeid };

        // Create a DynamicMethod. In this example the method has no
        // name. The return type of the method is int. The method 
        // has access to the protected and private data of the 
        // Example class.
        //
        DynamicMethod^ multiplyHidden = gcnew DynamicMethod(
            "", 
            int::typeid, 
            methodArgs2, 
            Example::typeid);

        // Emit the method body. In this example ILGenerator is used
        // to emit the MSIL. DynamicMethod has an associated type
        // DynamicILInfo that can be used in conjunction with 
        // unmanaged code generators.
        //
        // The MSIL loads the first argument, which is an instance of
        // the Example class, and uses it to load the value of a 
        // private instance field of type int. The second argument is
        // loaded, and the two numbers are multiplied. If the result
        // is larger than int, the value is truncated and the most 
        // significant bits are discarded. The method returns, with
        // the return value on the stack.
        //
        ILGenerator^ ilMH = multiplyHidden->GetILGenerator();
        ilMH->Emit(OpCodes::Ldarg_0);

        FieldInfo^ testInfo = Example::typeid->GetField("test",
            BindingFlags::NonPublic | BindingFlags::Instance);

        ilMH->Emit(OpCodes::Ldfld, testInfo);
        ilMH->Emit(OpCodes::Ldarg_1);
        ilMH->Emit(OpCodes::Mul);
        ilMH->Emit(OpCodes::Ret);

        // Create a delegate that represents the dynamic method. 
        // Creating the delegate completes the method, and any further 
        // attempts to change the method � for example, by adding more
        // MSIL � are ignored. 
        // 
        // The following code binds the method to a new instance
        // of the Example class whose private test field is set to 42.
        // That is, each time the delegate is invoked the instance of
        // Example is passed to the first parameter of the method.
        //
        // The delegate OneParameter is used, because the first
        // parameter of the method receives the instance of Example.
        // When the delegate is invoked, only the second parameter is
        // required. 
        //
        OneParameter<int, int>^ invoke = (OneParameter<int, int>^)
            multiplyHidden->CreateDelegate(
                OneParameter<int, int>::typeid, 
                gcnew Example(42)
            );

        Console::WriteLine("3 * test = {0}", invoke(3));
    }
};

void main()
{
    Example::Main();
}
/* This code example produces the following output:

123456789 squared = 15241578750190521
3 * test = 126
 */
using System;
using System.Reflection;
using System.Reflection.Emit;

public class Example
{
    // The following constructor and private field are used to
    // demonstrate a method bound to an object.
    private int test;
    public Example(int test) { this.test = test; }

    // Declare delegates that can be used to execute the completed
    // SquareIt dynamic method. The OneParameter delegate can be
    // used to execute any method with one parameter and a return
    // value, or a method with two parameters and a return value
    // if the delegate is bound to an object.
    //
    private delegate long SquareItInvoker(int input);

    private delegate TReturn OneParameter<TReturn, TParameter0>
        (TParameter0 p0);

    public static void Main()
    {
        // Example 1: A simple dynamic method.
        //
        // Create an array that specifies the parameter types for the
        // dynamic method. In this example the only parameter is an
        // int, so the array has only one element.
        //
        Type[] methodArgs = {typeof(int)};

        // Create a DynamicMethod. In this example the method is
        // named SquareIt. It is not necessary to give dynamic
        // methods names. They cannot be invoked by name, and two
        // dynamic methods can have the same name. However, the
        // name appears in calls stacks and can be useful for
        // debugging.
        //
        // In this example the return type of the dynamic method
        // is long. The method is associated with the module that
        // contains the Example class. Any loaded module could be
        // specified. The dynamic method is like a module-level
        // static method.
        //
        DynamicMethod squareIt = new DynamicMethod(
            "SquareIt",
            typeof(long),
            methodArgs,
            typeof(Example).Module);

        // Emit the method body. In this example ILGenerator is used
        // to emit the MSIL. DynamicMethod has an associated type
        // DynamicILInfo that can be used in conjunction with
        // unmanaged code generators.
        //
        // The MSIL loads the argument, which is an int, onto the
        // stack, converts the int to a long, duplicates the top
        // item on the stack, and multiplies the top two items on the
        // stack. This leaves the squared number on the stack, and
        // all the method has to do is return.
        //
        ILGenerator il = squareIt.GetILGenerator();
        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Conv_I8);
        il.Emit(OpCodes.Dup);
        il.Emit(OpCodes.Mul);
        il.Emit(OpCodes.Ret);

        // Create a delegate that represents the dynamic method.
        // Creating the delegate completes the method, and any further
        // attempts to change the method (for example, by adding more
        // MSIL) are ignored. The following code uses a generic
        // delegate that can produce delegate types matching any
        // single-parameter method that has a return type.
        //
        OneParameter<long, int> invokeSquareIt =
            (OneParameter<long, int>)
            squareIt.CreateDelegate(typeof(OneParameter<long, int>));

        Console.WriteLine("123456789 squared = {0}",
            invokeSquareIt(123456789));

        // Example 2: A dynamic method bound to an instance.
        //
        // Create an array that specifies the parameter types for a
        // dynamic method. If the delegate representing the method
        // is to be bound to an object, the first parameter must
        // match the type the delegate is bound to. In the following
        // code the bound instance is of the Example class.
        //
        Type[] methodArgs2 = { typeof(Example), typeof(int) };

        // Create a DynamicMethod. In this example the method has no
        // name. The return type of the method is int. The method
        // has access to the protected and private data of the
        // Example class.
        //
        DynamicMethod multiplyHidden = new DynamicMethod(
            "",
            typeof(int),
            methodArgs2,
            typeof(Example));

        // Emit the method body. In this example ILGenerator is used
        // to emit the MSIL. DynamicMethod has an associated type
        // DynamicILInfo that can be used in conjunction with
        // unmanaged code generators.
        //
        // The MSIL loads the first argument, which is an instance of
        // the Example class, and uses it to load the value of a
        // private instance field of type int. The second argument is
        // loaded, and the two numbers are multiplied. If the result
        // is larger than int, the value is truncated and the most
        // significant bits are discarded. The method returns, with
        // the return value on the stack.
        //
        ILGenerator ilMH = multiplyHidden.GetILGenerator();
        ilMH.Emit(OpCodes.Ldarg_0);

        FieldInfo testInfo = typeof(Example).GetField("test",
            BindingFlags.NonPublic | BindingFlags.Instance);

        ilMH.Emit(OpCodes.Ldfld, testInfo);
        ilMH.Emit(OpCodes.Ldarg_1);
        ilMH.Emit(OpCodes.Mul);
        ilMH.Emit(OpCodes.Ret);

        // Create a delegate that represents the dynamic method.
        // Creating the delegate completes the method, and any further
        // attempts to change the method — for example, by adding more
        // MSIL — are ignored.
        //
        // The following code binds the method to a new instance
        // of the Example class whose private test field is set to 42.
        // That is, each time the delegate is invoked the instance of
        // Example is passed to the first parameter of the method.
        //
        // The delegate OneParameter is used, because the first
        // parameter of the method receives the instance of Example.
        // When the delegate is invoked, only the second parameter is
        // required.
        //
        OneParameter<int, int> invoke = (OneParameter<int, int>)
            multiplyHidden.CreateDelegate(
                typeof(OneParameter<int, int>),
                new Example(42)
            );

        Console.WriteLine("3 * test = {0}", invoke(3));
    }
}
/* This code example produces the following output:

123456789 squared = 15241578750190521
3 * test = 126
 */
Imports System.Reflection
Imports System.Reflection.Emit

Public Class Example

    ' The following constructor and private field are used to
    ' demonstrate a method bound to an object.
    '
    Private test As Integer
    Public Sub New(ByVal test As Integer)
        Me.test = test
    End Sub

    ' Declare delegates that can be used to execute the completed 
    ' SquareIt dynamic method. The OneParameter delegate can be 
    ' used to execute any method with one parameter and a return
    ' value, or a method with two parameters and a return value
    ' if the delegate is bound to an object.
    '
    Private Delegate Function _
        SquareItInvoker(ByVal input As Integer) As Long

    Private Delegate Function _
        OneParameter(Of TReturn, TParameter0) _
        (ByVal p0 As TParameter0) As TReturn

    Public Shared Sub Main()

        ' Example 1: A simple dynamic method.
        '
        ' Create an array that specifies the parameter types for the
        ' dynamic method. In this example the only parameter is an 
        ' Integer, so the array has only one element.
        '
        Dim methodArgs As Type() = {GetType(Integer)}

        ' Create a DynamicMethod. In this example the method is
        ' named SquareIt. It is not necessary to give dynamic 
        ' methods names. They cannot be invoked by name, and two
        ' dynamic methods can have the same name. However, the 
        ' name appears in calls stacks and can be useful for
        ' debugging. 
        '
        ' In this example the return type of the dynamic method
        ' is Long. The method is associated with the module that 
        ' contains the Example class. Any loaded module could be
        ' specified. The dynamic method is like a module-level
        ' Shared method.
        '
        Dim squareIt As New DynamicMethod( _
            "SquareIt", _
            GetType(Long), _
            methodArgs, _
            GetType(Example).Module)

        ' Emit the method body. In this example ILGenerator is used
        ' to emit the MSIL. DynamicMethod has an associated type
        ' DynamicILInfo that can be used in conjunction with 
        ' unmanaged code generators.
        '
        ' The MSIL loads the argument, which is an Integer, onto the 
        ' stack, converts the Integer to a Long, duplicates the top
        ' item on the stack, and multiplies the top two items on the
        ' stack. This leaves the squared number on the stack, and 
        ' all the method has to do is return.
        '
        Dim il As ILGenerator = squareIt.GetILGenerator()
        il.Emit(OpCodes.Ldarg_0)
        il.Emit(OpCodes.Conv_I8)
        il.Emit(OpCodes.Dup)
        il.Emit(OpCodes.Mul)
        il.Emit(OpCodes.Ret)

        ' Create a delegate that represents the dynamic method. 
        ' Creating the delegate completes the method, and any further 
        ' attempts to change the method (for example, by adding more
        ' MSIL) are ignored. The following code uses a generic 
        ' delegate that can produce delegate types matching any
        ' single-parameter method that has a return type.
        '
        Dim invokeSquareIt As OneParameter(Of Long, Integer) = _
            CType( _
                squareIt.CreateDelegate( _
                    GetType(OneParameter(Of Long, Integer))), _
                OneParameter(Of Long, Integer) _
            )

        Console.WriteLine("123456789 squared = {0}", _
            invokeSquareIt(123456789))


        ' Example 2: A dynamic method bound to an instance.
        '
        ' Create an array that specifies the parameter types for a
        ' dynamic method. If the delegate representing the method
        ' is to be bound to an object, the first parameter must 
        ' match the type the delegate is bound to. In the following
        ' code the bound instance is of the Example class. 
        '
        Dim methodArgs2 As Type() = _
            {GetType(Example), GetType(Integer)}

        ' Create a DynamicMethod. In this example the method has no
        ' name. The return type of the method is Integer. The method 
        ' has access to the protected and private members of the 
        ' Example class. 
        '
        Dim multiplyPrivate As New DynamicMethod( _
            "", _
            GetType(Integer), _
            methodArgs2, _
            GetType(Example))

        ' Emit the method body. In this example ILGenerator is used
        ' to emit the MSIL. DynamicMethod has an associated type
        ' DynamicILInfo that can be used in conjunction with 
        ' unmanaged code generators.
        '
        ' The MSIL loads the first argument, which is an instance of
        ' the Example class, and uses it to load the value of a 
        ' private instance field of type Integer. The second argument 
        ' is loaded, and the two numbers are multiplied. If the result
        ' is larger than Integer, the value is truncated and the most 
        ' significant bits are discarded. The method returns, with
        ' the return value on the stack.
        '
        Dim ilMP As ILGenerator = multiplyPrivate.GetILGenerator()
        ilMP.Emit(OpCodes.Ldarg_0)

        Dim testInfo As FieldInfo = _
            GetType(Example).GetField("test", _
                BindingFlags.NonPublic Or BindingFlags.Instance)

        ilMP.Emit(OpCodes.Ldfld, testInfo)
        ilMP.Emit(OpCodes.Ldarg_1)
        ilMP.Emit(OpCodes.Mul)
        ilMP.Emit(OpCodes.Ret)

        ' Create a delegate that represents the dynamic method. 
        ' Creating the delegate completes the method, and any further 
        ' attempts to change the method  for example, by adding more
        ' MSIL  are ignored. 
        ' 
        ' The following code binds the method to a new instance
        ' of the Example class whose private test field is set to 42.
        ' That is, each time the delegate is invoked the instance of
        ' Example is passed to the first parameter of the method.
        '
        ' The delegate OneParameter is used, because the first
        ' parameter of the method receives the instance of Example.
        ' When the delegate is invoked, only the second parameter is
        ' required. 
        '
        Dim invoke As OneParameter(Of Integer, Integer) = _
            CType( _
                multiplyPrivate.CreateDelegate( _
                    GetType(OneParameter(Of Integer, Integer)), _
                    new Example(42) _
                ), _
                OneParameter(Of Integer, Integer) _
            )

        Console.WriteLine("3 * test = {0}", invoke(3))

    End Sub

End Class

' This code example produces the following output:
'
'123456789 squared = 15241578750190521
'3 * test = 126
' 

Vea tambiénSee also