MethodInfo.MakeGenericMethod(Type[]) Metodo

Definizione

Sostituisce con gli elementi di una matrice di tipi i parametri di tipo della definizione di metodo generica corrente e restituisce un oggetto MethodInfo che rappresenta il metodo costruito risultante.Substitutes the elements of an array of types for the type parameters of the current generic method definition, and returns a MethodInfo object representing the resulting constructed method.

public:
 virtual System::Reflection::MethodInfo ^ MakeGenericMethod(... cli::array <Type ^> ^ typeArguments);
public virtual System.Reflection.MethodInfo MakeGenericMethod (params Type[] typeArguments);
abstract member MakeGenericMethod : Type[] -> System.Reflection.MethodInfo
override this.MakeGenericMethod : Type[] -> System.Reflection.MethodInfo
Public Overridable Function MakeGenericMethod (ParamArray typeArguments As Type()) As MethodInfo

Parametri

typeArguments
Type[]

Matrice di tipi con cui sostituire i parametri di tipo della definizione del metodo generica corrente.An array of types to be substituted for the type parameters of the current generic method definition.

Restituisce

Oggetto MethodInfo che rappresenta il metodo costruito ottenuto sostituendo gli elementi di typeArguments per i parametri di tipo della definizione di metodo generica corrente.A MethodInfo object that represents the constructed method formed by substituting the elements of typeArguments for the type parameters of the current generic method definition.

Eccezioni

L'oggetto MethodInfo corrente non rappresenta una definizione di metodo generico.The current MethodInfo does not represent a generic method definition. Ciò significa che IsGenericMethodDefinition restituisce false.That is, IsGenericMethodDefinition returns false.

typeArguments è null.typeArguments is null.

-oppure--or- Qualsiasi elemento di typeArguments è null.Any element of typeArguments is null.

Il numero di elementi in typeArguments non è uguale al numero dei parametri di tipo della definizione di metodo generico corrente.The number of elements in typeArguments is not the same as the number of type parameters of the current generic method definition.

-oppure--or- Un elemento di typeArguments non soddisfa i vincoli specificati per il parametro di tipo corrispondente della definizione di metodo generico corrente.An element of typeArguments does not satisfy the constraints specified for the corresponding type parameter of the current generic method definition.

Questo metodo non è supportato.This method is not supported.

Esempi

Nell'esempio di codice riportato di seguito vengono illustrate le proprietà e i metodi di MethodInfo che supportano l'analisi dei metodi generici.The following code example demonstrates the properties and methods of MethodInfo that support the examination of generic methods. L'esempio effettua le seguenti operazioni:The example does the following:

  • Definisce una classe che dispone di un metodo generico.Defines a class that has a generic method.

  • Crea un MethodInfo che rappresenta il metodo generico.Creates a MethodInfo that represents the generic method.

  • Visualizza le proprietà della definizione del metodo generico.Displays properties of the generic method definition.

  • Assegna gli argomenti di tipo ai parametri di tipo del MethodInfoe richiama il metodo generico costruito risultante.Assigns type arguments to the type parameters of the MethodInfo, and invokes the resulting constructed generic method.

  • Visualizza le proprietà del metodo generico costruito.Displays properties of the constructed generic method.

  • Recupera la definizione di metodo generico dal metodo costruito e la confronta con la definizione originale.Retrieves the generic method definition from the constructed method and compares it to the original definition.

using namespace System;
using namespace System::Reflection;

// Define a class with a generic method.
ref class Example
{
public:
    generic<typename T> static void Generic(T toDisplay)
    {
        Console::WriteLine("\r\nHere it is: {0}", toDisplay);
    }
};

void DisplayGenericMethodInfo(MethodInfo^ mi)
{
    Console::WriteLine("\r\n{0}", mi);

    Console::WriteLine("\tIs this a generic method definition? {0}", 
        mi->IsGenericMethodDefinition);

    Console::WriteLine("\tIs it a generic method? {0}", 
        mi->IsGenericMethod);

    Console::WriteLine("\tDoes it have unassigned generic parameters? {0}", 
        mi->ContainsGenericParameters);

    // If this is a generic method, display its type arguments.
    //
    if (mi->IsGenericMethod)
    {
        array<Type^>^ typeArguments = mi->GetGenericArguments();

        Console::WriteLine("\tList type arguments ({0}):", 
            typeArguments->Length);

        for each (Type^ tParam in typeArguments)
        {
            // IsGenericParameter is true only for generic type
            // parameters.
            //
            if (tParam->IsGenericParameter)
            {
                Console::WriteLine("\t\t{0}  parameter position {1}" +
                    "\n\t\t   declaring method: {2}",
                    tParam,
                    tParam->GenericParameterPosition,
                    tParam->DeclaringMethod);
            }
            else
            {
                Console::WriteLine("\t\t{0}", tParam);
            }
        }
    }
};

void main()
{
    Console::WriteLine("\r\n--- Examine a generic method.");

    // Create a Type object representing class Example, and
    // get a MethodInfo representing the generic method.
    //
    Type^ ex = Example::typeid;
    MethodInfo^ mi = ex->GetMethod("Generic");

    DisplayGenericMethodInfo(mi);

    // Assign the int type to the type parameter of the Example 
    // method.
    //
    MethodInfo^ miConstructed = mi->MakeGenericMethod(int::typeid);

    DisplayGenericMethodInfo(miConstructed);

    // Invoke the method.
    array<Object^>^ args = { 42 };
    miConstructed->Invoke((Object^) 0, args);

    // Invoke the method normally.
    Example::Generic<int>(42);

    // Get the generic type definition from the closed method,
    // and show it's the same as the original definition.
    //
    MethodInfo^ miDef = miConstructed->GetGenericMethodDefinition();
    Console::WriteLine("\r\nThe definition is the same: {0}",
            miDef == mi);
};
        
/* This example produces the following output:

--- Examine a generic method.

Void Generic[T](T)
        Is this a generic method definition? True
        Is it a generic method? True
        Does it have unassigned generic parameters? True
        List type arguments (1):
                T  parameter position 0
                   declaring method: Void Generic[T](T)

Void Generic[Int32](Int32)
        Is this a generic method definition? False
        Is it a generic method? True
        Does it have unassigned generic parameters? False
        List type arguments (1):
                System.Int32

Here it is: 42

Here it is: 42

The definition is the same: True

 */
using System;
using System.Reflection;

// Define a class with a generic method.
public class Example
{
    public static void Generic<T>(T toDisplay)
    {
        Console.WriteLine("\r\nHere it is: {0}", toDisplay);
    }
}

public class Test
{
    public static void Main()
    {
        Console.WriteLine("\r\n--- Examine a generic method.");

        // Create a Type object representing class Example, and
        // get a MethodInfo representing the generic method.
        //
        Type ex = typeof(Example);
        MethodInfo mi = ex.GetMethod("Generic");

        DisplayGenericMethodInfo(mi);

        // Assign the int type to the type parameter of the Example 
        // method.
        //
        MethodInfo miConstructed = mi.MakeGenericMethod(typeof(int));

        DisplayGenericMethodInfo(miConstructed);

        // Invoke the method.
        object[] args = {42};
        miConstructed.Invoke(null, args);

        // Invoke the method normally.
        Example.Generic<int>(42);

        // Get the generic type definition from the closed method,
        // and show it's the same as the original definition.
        //
        MethodInfo miDef = miConstructed.GetGenericMethodDefinition();
        Console.WriteLine("\r\nThe definition is the same: {0}",
            miDef == mi);
    }
        
    private static void DisplayGenericMethodInfo(MethodInfo mi)
    {
        Console.WriteLine("\r\n{0}", mi);

        Console.WriteLine("\tIs this a generic method definition? {0}", 
            mi.IsGenericMethodDefinition);

        Console.WriteLine("\tIs it a generic method? {0}", 
            mi.IsGenericMethod);

        Console.WriteLine("\tDoes it have unassigned generic parameters? {0}", 
            mi.ContainsGenericParameters);

        // If this is a generic method, display its type arguments.
        //
        if (mi.IsGenericMethod)
        {
            Type[] typeArguments = mi.GetGenericArguments();

            Console.WriteLine("\tList type arguments ({0}):", 
                typeArguments.Length);

            foreach (Type tParam in typeArguments)
            {
                // IsGenericParameter is true only for generic type
                // parameters.
                //
                if (tParam.IsGenericParameter)
                {
                    Console.WriteLine("\t\t{0}  parameter position {1}" +
                        "\n\t\t   declaring method: {2}",
                        tParam,
                        tParam.GenericParameterPosition,
                        tParam.DeclaringMethod);
                }
                else
                {
                    Console.WriteLine("\t\t{0}", tParam);
                }
            }
        }
    }
}

/* This example produces the following output:

--- Examine a generic method.

Void Generic[T](T)
        Is this a generic method definition? True
        Is it a generic method? True
        Does it have unassigned generic parameters? True
        List type arguments (1):
                T  parameter position 0
                   declaring method: Void Generic[T](T)

Void Generic[Int32](Int32)
        Is this a generic method definition? False
        Is it a generic method? True
        Does it have unassigned generic parameters? False
        List type arguments (1):
                System.Int32

Here it is: 42

Here it is: 42

The definition is the same: True

 */
Imports System.Reflection

' Define a class with a generic method.
Public Class Example
    Public Shared Sub Generic(Of T)(ByVal toDisplay As T)
        Console.WriteLine(vbCrLf & "Here it is: {0}", toDisplay)
    End Sub
End Class

Public Class Test
    Public Shared Sub Main() 
        Console.WriteLine(vbCrLf & "--- Examine a generic method.")
        
        ' Create a Type object representing class Example, and
        ' get a MethodInfo representing the generic method.
        '
        Dim ex As Type = GetType(Example)
        Dim mi As MethodInfo = ex.GetMethod("Generic")
        
        DisplayGenericMethodInfo(mi)
        
        ' Assign the Integer type to the type parameter of the Example 
        ' method.
        '
        Dim arguments() As Type = { GetType(Integer) }
        Dim miConstructed As MethodInfo = mi.MakeGenericMethod(arguments)
        
        DisplayGenericMethodInfo(miConstructed)

        ' Invoke the method.
        Dim args() As Object = { 42 }
        miConstructed.Invoke(Nothing, args)
        
        ' Invoke the method normally.
        Example.Generic(Of Integer)(42)
        
        ' Get the generic type definition from the constructed method,
        ' and show that it's the same as the original definition.
        '
        Dim miDef As MethodInfo = miConstructed.GetGenericMethodDefinition()
        Console.WriteLine(vbCrLf & "The definition is the same: {0}", _
            miDef Is mi)
    End Sub
      
    Private Shared Sub DisplayGenericMethodInfo(ByVal mi As MethodInfo) 
        Console.WriteLine(vbCrLf & mi.ToString())
        
        Console.WriteLine(vbTab _
            & "Is this a generic method definition? {0}", _
            mi.IsGenericMethodDefinition)

        Console.WriteLine(vbTab & "Is it a generic method? {0}", _
            mi.IsGenericMethod)

        Console.WriteLine(vbTab _
            & "Does it have unassigned generic parameters? {0}", _
            mi.ContainsGenericParameters)

        ' If this is a generic method, display its type arguments.
        '
        If mi.IsGenericMethod Then
            Dim typeArguments As Type() = mi.GetGenericArguments()
            
            Console.WriteLine(vbTab & "List type arguments ({0}):", _
                typeArguments.Length)
            
            For Each tParam As Type In typeArguments
                ' IsGenericParameter is true only for generic type
                ' parameters.
                '
                If tParam.IsGenericParameter Then
                    Console.WriteLine(vbTab & vbTab _
                        & "{0}  parameter position: {1}" _
                        & vbCrLf & vbTab & vbTab _
                        & "   declaring method: {2}", _
                        tParam,  _
                        tParam.GenericParameterPosition, _
                        tParam.DeclaringMethod)
                Else
                    Console.WriteLine(vbTab & vbTab & tParam.ToString())
                End If
            Next tParam
        End If
    End Sub 
End Class 

' This example produces the following output:
'
'--- Examine a generic method.
'
'Void Generic[T](T)
'        Is this a generic method definition? True
'        Is it a generic method? True
'        Does it have unassigned generic parameters? True
'        List type arguments (1):
'                T  parameter position: 0
'                   declaring method: Void Generic[T](T)
'
'Void Generic[Int32](Int32)
'        Is this a generic method definition? False
'        Is it a generic method? True
'        Does it have unassigned generic parameters? False
'        List type arguments (1):
'                System.Int32
'
'Here it is: 42
'
'Here it is: 42
'
'The definition is the same: True
'

Commenti

Il MakeGenericMethod metodo consente di scrivere codice che assegna tipi specifici ai parametri di tipo della definizione di un metodo generico, creando in tal modo un oggetto MethodInfo che rappresenta un particolare metodo costruito.The MakeGenericMethod method allows you to write code that assigns specific types to the type parameters of a generic method definition, thus creating a MethodInfo object that represents a particular constructed method. Se la proprietà ContainsGenericParameters di questo oggetto MethodInfo restituisce true, è possibile utilizzarla per richiamare il metodo o per creare un delegato per richiamare il metodo.If the ContainsGenericParameters property of this MethodInfo object returns true, you can use it to invoke the method or to create a delegate to invoke the method.

I metodi costruiti con il metodo MakeGenericMethod possono essere aperti, ovvero alcuni degli argomenti di tipo possono essere parametri di tipo dei tipi generici di inclusione.Methods constructed with the MakeGenericMethod method can be open, that is, some of their type arguments can be type parameters of enclosing generic types. È possibile utilizzare tali metodi costruiti aperti quando si generano assembly dinamici.You might use such open constructed methods when you generate dynamic assemblies. Si consideri, ad C#esempio, i seguenti C++ Visual Basic e il codice.For example, consider the following C#, Visual Basic, and C++ code.

class C  
{  
    T N<T,U>(T t, U u) {...}  
    public V M<V>(V v)  
    {  
        return N<V,int>(v, 42);  
    }  
}  
  
Class C  
    Public Function N(Of T,U)(ByVal ta As T, ByVal ua As U) As T  
        ...  
    End Function  
    Public Function M(Of V)(ByVal va As V ) As V  
        Return N(Of V, Integer)(va, 42)  
    End Function  
End Class  
  
ref class C  
{  
private:  
    generic <typename T, typename U> T N(T t, U u) {...}  
public:  
    generic <typename V> V M(V v)  
    {  
        return N<V, int>(v, 42);  
    }  
};  

Il corpo del metodo di M contiene una chiamata al metodo N, specificando il parametro di tipo di M e il tipo Int32.The method body of M contains a call to method N, specifying the type parameter of M and the type Int32. La proprietà IsGenericMethodDefinition restituisce false per N<V,int>di metodo.The IsGenericMethodDefinition property returns false for method N<V,int>. La proprietà ContainsGenericParameters restituisce true, pertanto non è possibile richiamare il metodo N<V,int>.The ContainsGenericParameters property returns true, so method N<V,int> cannot be invoked.

Per un elenco delle condizioni invariabili per i termini specifici dei metodi generici, vedere la proprietà IsGenericMethod.For a list of the invariant conditions for terms specific to generic methods, see the IsGenericMethod property. Per un elenco delle condizioni invariabili per altri termini usati nella reflection generica, vedere la proprietà IsGenericType.For a list of the invariant conditions for other terms used in generic reflection, see the IsGenericType property.

Si applica a

Vedi anche