Type.GenericParameterPosition Eigenschaft

Definition

Ruft die Position des Typparameters in der Typparameterliste des generischen Typs oder der Methode ab, der bzw. die den Parameter deklariert hat, wenn das Type-Objekt einen Typparameter eines generischen Typs oder einer generischen Methode darstellt.Gets the position of the type parameter in the type parameter list of the generic type or method that declared the parameter, when the Type object represents a type parameter of a generic type or a generic method.

public:
 virtual property int GenericParameterPosition { int get(); };
public virtual int GenericParameterPosition { get; }
member this.GenericParameterPosition : int
Public Overridable ReadOnly Property GenericParameterPosition As Integer

Eigenschaftswert

Die Position eines Typparameters in der Typparameterliste des generischen Typs oder der generischen Methode, der bzw. die den Parameter definiert.The position of a type parameter in the type parameter list of the generic type or method that defines the parameter. Die Positionsnummern beginnen mit 0.Position numbers begin at 0.

Ausnahmen

Der aktuelle Typ stellt keinen Typparameter dar.The current type does not represent a type parameter. Das heißt, IsGenericParameter gibt false zurück.That is, IsGenericParameter returns false.

Beispiele

Im folgenden Beispiel wird eine generische Klasse mit zwei Typparametern definiert und eine zweite generische Klasse definiert, die von der ersten Klasse abgeleitet wird.The following example defines a generic class with two type parameters and defines a second generic class that derives from the first class. Die Basisklasse der abgeleiteten Klasse hat zwei Typargumente: Int32die erste ist, und die zweite ist ein Typparameter des abgeleiteten Typs.The derived class's base class has two type arguments: the first is Int32, and the second is a type parameter of the derived type. Das Beispiel zeigt Informationen zu diesen generischen Klassen, einschließlich der von der GenericParameterPosition -Eigenschaft gemeldeten Positionen.The example displays information about these generic classes, including the positions reported by the GenericParameterPosition property.

using namespace System;
using namespace System::Reflection;
using namespace System::Collections::Generic;

// Define a base class with two type parameters.
generic< class T,class U >
public ref class Base {};

// Define a derived class. The derived class inherits from a constructed
// class that meets the following criteria:
//   (1) Its generic type definition is Base<T, U>.
//   (2) It specifies int for the first type parameter.
//   (3) For the second type parameter, it uses the same type that is used
//       for the type parameter of the derived class.
// Thus, the derived class is a generic type with one type parameter, but
// its base class is an open constructed type with one type argument and
// one type parameter.
generic<class V>
public ref class Derived : Base<int,V> {};

public ref class Test
{
public:
    static void Main()
    {
        Console::WriteLine( 
            L"\r\n--- Display a generic type and the open constructed");
        Console::WriteLine(L"    type from which it is derived.");
      
        // Create a Type object representing the generic type definition
        // for the Derived type. Note the absence of type arguments.
        //
        Type^ derivedType = Derived::typeid;
        DisplayGenericTypeInfo(derivedType);
      
        // Display its open constructed base type.
        DisplayGenericTypeInfo(derivedType->BaseType);
    }


private:
    static void DisplayGenericTypeInfo(Type^ t)
    {
        Console::WriteLine(L"\r\n{0}", t);
        Console::WriteLine(L"\tIs this a generic type definition? {0}",
            t->IsGenericTypeDefinition);
        Console::WriteLine(L"\tIs it a generic type? {0}", t->IsGenericType);
        Console::WriteLine(L"\tDoes it have unassigned generic parameters? {0}",
            t->ContainsGenericParameters);
        if (t->IsGenericType)
        {
         
            // If this is a generic type, display the type arguments.
            //
            array<Type^>^typeArguments = t->GetGenericArguments();
            Console::WriteLine(L"\tList type arguments ({0}):",
                typeArguments->Length);
            System::Collections::IEnumerator^ myEnum = 
                typeArguments->GetEnumerator();
            while (myEnum->MoveNext())
            {
                Type^ tParam = safe_cast<Type^>(myEnum->Current);
            
                // IsGenericParameter is true only for generic type
                // parameters.
                //
                if (tParam->IsGenericParameter)
                {
                    Console::WriteLine( 
                        L"\t\t{0}  (unassigned - parameter position {1})", 
                        tParam, tParam->GenericParameterPosition);
                }
                else
                {
                    Console::WriteLine(L"\t\t{0}", tParam);
                }
            }
        }
    }
};

int main()
{
    Test::Main();
}

/* This example produces the following output:

--- Display a generic type and the open constructed
    type from which it is derived.

Derived`1[V]
        Is this a generic type definition? True
        Is it a generic type? True
        Does it have unassigned generic parameters? True
        List type arguments (1):
                V  (unassigned - parameter position 0)

Base`2[System.Int32,V]
        Is this a generic type definition? False
        Is it a generic type? True
        Does it have unassigned generic parameters? True
        List type arguments (2):
                System.Int32
                V  (unassigned - parameter position 0)
 */
using System;
using System.Reflection;
using System.Collections.Generic;

// Define a base class with two type parameters.
public class Base<T, U> { }

// Define a derived class. The derived class inherits from a constructed
// class that meets the following criteria:
//   (1) Its generic type definition is Base<T, U>.
//   (2) It specifies int for the first type parameter.
//   (3) For the second type parameter, it uses the same type that is used
//       for the type parameter of the derived class.
// Thus, the derived class is a generic type with one type parameter, but
// its base class is an open constructed type with one type argument and
// one type parameter.
public class Derived<V> : Base<int, V> { }

public class Test
{
    public static void Main()
    {
        Console.WriteLine(
            "\r\n--- Display a generic type and the open constructed");
        Console.WriteLine("    type from which it is derived.");

        // Create a Type object representing the generic type definition 
        // for the Derived type, by omitting the type argument. (For
        // types with multiple type parameters, supply the commas but
        // omit the type arguments.) 
        //
        Type derivedType = typeof(Derived<>);
        DisplayGenericTypeInfo(derivedType);

        // Display its open constructed base type.
        DisplayGenericTypeInfo(derivedType.BaseType);
    }

    private static void DisplayGenericTypeInfo(Type t)
    {
        Console.WriteLine("\r\n{0}", t);

        Console.WriteLine("\tIs this a generic type definition? {0}", 
            t.IsGenericTypeDefinition);

        Console.WriteLine("\tIs it a generic type? {0}", 
            t.IsGenericType);

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

        if (t.IsGenericType)
        {
            // If this is a generic type, display the type arguments.
            //
            Type[] typeArguments = t.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}  (unassigned - parameter position {1})",
                        tParam,
                        tParam.GenericParameterPosition);
                }
                else
                {
                    Console.WriteLine("\t\t{0}", tParam);
                }
            }
        }
    }
}

/* This example produces the following output:

--- Display a generic type and the open constructed
    type from which it is derived.

Derived`1[V]
        Is this a generic type definition? True
        Is it a generic type? True
        Does it have unassigned generic parameters? True
        List type arguments (1):
                V  (unassigned - parameter position 0)

Base`2[System.Int32,V]
        Is this a generic type definition? False
        Is it a generic type? True
        Does it have unassigned generic parameters? True
        List type arguments (2):
                System.Int32
                V  (unassigned - parameter position 0)
 */
Imports System.Reflection
Imports System.Collections.Generic

' Define a base class with two type parameters.
Public Class Base(Of T, U)
End Class

' Define a derived class. The derived class inherits from a constructed
' class that meets the following criteria:
'   (1) Its generic type definition is Base<T, U>.
'   (2) It uses int for the first type parameter.
'   (3) For the second type parameter, it uses the same type that is used
'       for the type parameter of the derived class.
' Thus, the derived class is a generic type with one type parameter, but
' its base class is an open constructed type with one assigned type
' parameter and one unassigned type parameter.
Public Class Derived(Of V)
    Inherits Base(Of Integer, V)
End Class

Public Class Test
    
    Public Shared Sub Main() 
        Console.WriteLine(vbCrLf _
            & "--- Display a generic type and the open constructed")
        Console.WriteLine("    type from which it is derived.")
        
        ' Create a Type object representing the generic type definition 
        ' for the Derived type, by omitting the type argument. (For
        ' types with multiple type parameters, supply the commas but
        ' omit the type arguments.) 
        '
        Dim derivedType As Type = GetType(Derived(Of ))
        DisplayGenericTypeInfo(derivedType)
        
        ' Display its open constructed base type.
        DisplayGenericTypeInfo(derivedType.BaseType)
    
    End Sub
    
    Private Shared Sub DisplayGenericTypeInfo(ByVal t As Type) 
        Console.WriteLine(vbCrLf & "{0}", t)
        
        Console.WriteLine(vbTab & "Is this a generic type definition? " _
            & t.IsGenericTypeDefinition)
        
        Console.WriteLine(vbTab & "Is it a generic type? " _
            & t.IsGenericType)
        
        Console.WriteLine(vbTab _
            & "Does it have unassigned generic parameters? " _
            & t.ContainsGenericParameters)
        
        If t.IsGenericType Then
            ' If this is a generic type, display the type arguments.
            '
            Dim typeArguments As Type() = t.GetGenericArguments()
            
            Console.WriteLine(vbTab & "List type arguments (" _
                & 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 & tParam.ToString() _
                        & "  (unassigned - parameter position " _
                        & tParam.GenericParameterPosition & ")")
                Else
                    Console.WriteLine(vbTab & vbTab & tParam.ToString())
                End If
            Next tParam
        End If
    
    End Sub
End Class

' This example produces the following output:
'
'--- Display a generic type and the open constructed
'    type from which it is derived.
'
'Derived`1[V]
'        Is this a generic type definition? True
'        Is it a generic type? True
'        Does it have unassigned generic parameters? True
'        List type arguments (1):
'                V  (unassigned - parameter position 0)
'
'Base`2[System.Int32,V]
'        Is this a generic type definition? False
'        Is it a generic type? True
'        Does it have unassigned generic parameters? True
'        List type parameters (2):
'                System.Int32
'                V  (unassigned - parameter position 0)
' 

Hinweise

Die GenericParameterPosition -Eigenschaft gibt die Position eines Typparameters in der Parameterliste der generischen Typdefinition oder der generischen Methoden Definition zurück, in der der Typparameter ursprünglich definiert wurde.The GenericParameterPosition property returns the position of a type parameter in the parameter list of the generic type definition or generic method definition where the type parameter was originally defined. Die DeclaringType Eigenschaften DeclaringMethod und identifizieren den generischen Typ oder die Definition der Methode:The DeclaringType and DeclaringMethod properties identify the generic type or method definition:

  • , Wenn DeclaringMethod die-Eigenschaft MethodInfoein- MethodInfo Objekt zurückgibt, das eine generische Methoden Definition Type darstellt, und das aktuelle-Objekt einen Typparameter dieser generischen Methoden Definition darstellt.If the DeclaringMethod property returns a MethodInfo, that MethodInfo represents a generic method definition, and the current Type object represents a type parameter of that generic method definition.

  • Wenn die DeclaringMethod -Eigenschaft nullzurückgibt, DeclaringType gibt die-Eigenschaft Type immer ein-Objekt zurück, das eine generische Typdefinition darstellt, und das aktuelle Type -Objekt stellt einen Typparameter dieses generischen Typs dar. Definition.If the DeclaringMethod property returns null, then the DeclaringType property always returns a Type object representing a generic type definition, and the current Type object represents a type parameter of that generic type definition.

Um den korrekten Kontext für den Wert der GenericParameterPosition -Eigenschaft bereitzustellen, müssen Sie den generischen Typ oder die Methode identifizieren, zu der ein Typparameter gehört.To provide the correct context for the value of the GenericParameterPosition property, it is necessary to identify the generic type or method a type parameter belongs to. Sehen Sie sich beispielsweise den Rückgabewert der generischen GetSomething -Methode im folgenden Code an:For example, consider the return value of the generic method GetSomething in the following code:

generic<typename T, typename U> public ref class B { };
generic<typename V> public ref class A
{
public:
    generic<typename X> B<V, X>^ GetSomething()
    {
        return gcnew B<V, X>();
    }
};
public class B<T, U> { }
public class A<V>
{
    public B<V, X> GetSomething<X>()
    {
        return new B<V, X>();
    }
}
Public Class B(Of T, U)
End Class
Public Class A(Of V)
    Public Function GetSomething(Of X)() As B(Of V, X)
        Return New B(Of V, X)()
    End Function
End Class

Der Typ, der GetSomething von zurückgegeben wird, hängt von den A Typargumenten ab, die für die Klasse und GetSomethingThe type returned by GetSomething depends on the type arguments supplied to class A and to GetSomething itself. Sie können einen MethodInfo für GetSomethingund den Rückgabetyp abrufen.You can obtain a MethodInfo for GetSomething, and from that you can obtain the return type. Wenn Sie die Typparameter des Rückgabe Typs überprüfen, GenericParameterPosition gibt 0 für beides zurück.When you examine the type parameters of the return type, GenericParameterPosition returns 0 for both. Die Position von V ist 0, V da der erste Typparameter in der Typparameter Liste für die A-Klasse ist.The position of V is 0 because V is the first type parameter in the type parameter list for class A. Die Position von X ist 0, X da der erste Typparameter in der Typparameter Liste für GetSomethingist.The position of X is 0 because X is the first type parameter in the type parameter list for GetSomething.

Hinweis

Wenn Sie GenericParameterPosition die-Eigenschaft aufrufen, wird eine Type Ausnahme ausgelöst, wenn der aktuelle keinen Typparameter darstellt.Calling the GenericParameterPosition property causes an exception if the current Type does not represent a type parameter. Wenn Sie die Typargumente eines geöffneten konstruierten Typs überprüfen IsGenericParameter , verwenden Sie die-Eigenschaft, um zu ermitteln, welche Typparameter und welche Typen sind.When you examine the type arguments of an open constructed type, use the IsGenericParameter property to tell which are type parameters and which are types. Die IsGenericParameter -Eigenschaft true gibt für einen Typparameter zurück. Sie können dann GenericParameterPosition die-Methode verwenden, um Ihre Position DeclaringMethod abzurufen DeclaringType , und die-Eigenschaft und die-Eigenschaft verwenden, um die generische Methode oder Typdefinition zu bestimmen .The IsGenericParameter property returns true for a type parameter; you can then use the GenericParameterPosition method to obtain its position and use the DeclaringMethod and DeclaringType properties to determine the generic method or type definition that defines it.

Gilt für:

Siehe auch