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Metodo DynamicMethod.CreateDelegate (Type)

 

Data di pubblicazione: ottobre 2016

Completa il metodo dinamico e crea un delegato che può essere usato per eseguirlo.

Spazio dei nomi:   System.Reflection.Emit
Assembly:  mscorlib (in mscorlib.dll)

[ComVisibleAttribute(true)]
public override sealed Delegate CreateDelegate(
	Type delegateType
)

Parametri

delegateType
Type: System.Type

Tipo delegato la cui firma corrisponde a quella del metodo dinamico.

Valore restituito

Type: System.Delegate

Delegato del tipo specificato, che può essere usato per eseguire il metodo dinamico.

Exception Condition
InvalidOperationException

Il metodo dinamico non contiene alcun corpo.

ArgumentException

delegateType contiene un numero errato di parametri o tipi di parametro non validi.

Calling the M:System.Reflection.Emit.DynamicMethod.CreateDelegate(System.Type) method or the Overload:System.Reflection.Emit.DynamicMethod.Invoke method completes the dynamic method. Any further attempt to alter the dynamic method, such as modifying parameter definitions or emitting more Microsoft intermediate language (MSIL), is ignored; no exception is thrown.

To create a method body for a dynamic method when you have your own MSIL generator, call the M:System.Reflection.Emit.DynamicMethod.GetDynamicILInfo method to obtain a T:System.Reflection.Emit.DynamicILInfo object. If you do not have your own MSIL generator, call the Overload:System.Reflection.Emit.DynamicMethod.GetILGenerator method to obtain an T:System.Reflection.Emit.ILGenerator object that can be used to generate the method body.

The following code example creates a dynamic method that takes two parameters. The example emits a simple function body that prints the first parameter to the console, and the example uses the second parameter as the return value of the method. The example completes the method by creating a delegate, invokes the delegate with different parameters, and finally invokes the dynamic method using the Overload:System.Reflection.Emit.DynamicMethod.Invoke method.

using System;
using System.Reflection;
using System.Reflection.Emit;
using Microsoft.VisualBasic;

public class Test
{
    // Declare a delegate that will be used to execute the completed
    // dynamic method. 
    private delegate int HelloInvoker(string msg, int ret);

    public static void Main()
    {
        // Create an array that specifies the types of the parameters
        // of the dynamic method. This method has a string parameter
        // and an int parameter.
        Type[] helloArgs = {typeof(string), typeof(int)};

        // Create a dynamic method with the name "Hello", a return type
        // of int, and two parameters whose types are specified by the
        // array helloArgs. Create the method in the module that
        // defines the Test class.
        DynamicMethod hello = new DynamicMethod("Hello", 
            typeof(int), 
            helloArgs, 
            typeof(Test).Module);

        // Create an array that specifies the parameter types of the
        // overload of Console.WriteLine to be used in Hello.
        Type[] writeStringArgs = {typeof(string)};
        // Get the overload of Console.WriteLine that has one
        // String parameter.
        MethodInfo writeString = 
            typeof(Console).GetMethod("WriteLine", writeStringArgs);

        // Get an ILGenerator and emit a body for the dynamic method.
        ILGenerator il = hello.GetILGenerator();
        // Load the first argument, which is a string, onto the stack.
        il.Emit(OpCodes.Ldarg_0);
        // Call the overload of Console.WriteLine that prints a string.
        il.EmitCall(OpCodes.Call, writeString, null);
        // The Hello method returns the value of the second argument;
        // to do this, load the onto the stack and return.
        il.Emit(OpCodes.Ldarg_1);
        il.Emit(OpCodes.Ret);

        // Create a delegate that represents the dynamic method. This
        // action completes the method, and any further attempts to
        // change the method will cause an exception.
        HelloInvoker hi = 
            (HelloInvoker) hello.CreateDelegate(typeof(HelloInvoker));

        // Use the delegate to execute the dynamic method. Save and
        // print the return value.
        int retval = hi("\r\nHello, World!", 42);
        Console.WriteLine("Executing delegate hi(\"Hello, World!\", 42) returned {0}",
            retval);

        // Do it again, with different arguments.
        retval = hi("\r\nHi, Mom!", 5280);
        Console.WriteLine("Executing delegate hi(\"Hi, Mom!\", 5280) returned {0}",
            retval);

        // Create an array of arguments to use with the Invoke method.
        object[] invokeArgs = {"\r\nHello, World!", 42};
        // Invoke the dynamic method using the arguments. This is much
        // slower than using the delegate, because you must create an
        // array to contain the arguments, and ValueType arguments
        // must be boxed.
        object objRet = hello.Invoke(null, invokeArgs);
        Console.WriteLine("hello.Invoke returned {0}", objRet);
    }
}

.NET Framework
Disponibile da 2.0
Libreria di classi portabile
Supportato in: piattaforme .NET portabili
Silverlight
Disponibile da 2.0
Windows Phone Silverlight
Disponibile da 7.1
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