Type.MakeGenericType(Type[]) 方法

定义

命名空间:

System

程序集:

System.Runtime.dll

Source:

Type.cs

替代由当前泛型类型定义的类型参数组成的类型数组的元素，并返回表示结果构造类型的 Type 对象。

public:
 virtual Type ^ MakeGenericType(... cli::array <Type ^> ^ typeArguments);

public virtual Type MakeGenericType (params Type[] typeArguments);

abstract member MakeGenericType : Type[] -> Type
override this.MakeGenericType : Type[] -> Type

Public Overridable Function MakeGenericType (ParamArray typeArguments As Type()) As Type

参数

typeArguments

Type[]

将代替当前泛型类型的类型参数的类型数组。

返回

Type

Type 表示的构造类型通过以下方式形成：用 typeArguments 的元素取代当前泛型类型的类型参数。

例外

InvalidOperationException

当前的类型不表示泛型类型定义。 也就是说，IsGenericTypeDefinition 返回 false。

ArgumentNullException

typeArguments 为 null。

或

typeArguments 的任意元素为 null。

ArgumentException

typeArguments 中的元素数与当前泛型类型定义中的类型参数数不同。

或

typeArguments 的所有元素都不满足为当前泛型类型的相应类型参数指定的约束。

或

typeArguments 包含一个元素，该元素是一个指针类型（IsPointer 返回 true）、by-ref 类型（IsByRef 返回 true）或 Void。

NotSupportedException

基类不支持调用的方法。 派生类必须提供一个实现。

示例

下面的示例使用 MakeGenericType 方法根据类型的泛型类型定义 Dictionary<TKey,TValue> 创建构造类型。 构造的类型表示 Dictionary<TKey,TValue> 具有字符串键的 Test 对象的 。

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

namespace Example
{
    public ref class Test
    {
    public:
        static void CreateConstructedType(void)
        {      
            Console::WriteLine("\r\n--- Create a constructed type"
                " from the generic Dictionary`2 type.");
            
            // Create a type object representing 
            // the generic Dictionary`2 type.
            Type^ genericType = Type::GetType(
                "System.Collections.Generic.Dictionary`2");
            if (genericType != nullptr)
            {  
                DisplayTypeInfo(genericType);
            }
            else
            {
                Console::WriteLine("The type is not found");
                return;
            }
            
            // Create an array of types to substitute for the type
            // parameters of Dictionary`2. 
            // The key is of type string, and the type to be 
            // contained in the Dictionary`2 is Test.
            array<Type^>^ typeArgs = {String::typeid, Test::typeid};
            Type^ constructedType = 
                genericType->MakeGenericType(typeArgs);
            DisplayTypeInfo(constructedType);
            
            // Compare the type objects obtained above to type objects
            // obtained using typeof() and GetGenericTypeDefinition().
            Console::WriteLine("\r\n--- Compare types obtained by"
                " different methods:");

            Type^ definedType = Dictionary<String^, Test^>::typeid;
            Console::WriteLine("\tAre the constructed types "
                "equal? {0}", definedType == constructedType);
            Console::WriteLine("\tAre the generic types equal? {0}", 
                definedType->GetGenericTypeDefinition() == genericType);
        }

    private:
        static void DisplayTypeInfo(Type^ typeToDisplay)
        {   
            Console::WriteLine("\r\n{0}", typeToDisplay);
            Console::WriteLine("\tIs this a generic type definition? "
                "{0}", typeToDisplay->IsGenericTypeDefinition);
            Console::WriteLine("\tIs it a generic type? "
                "{0}", typeToDisplay->IsGenericType);
            
            array<Type^>^ typeArguments = 
                typeToDisplay->GetGenericArguments();
            Console::WriteLine("\tList type arguments ({0}):", 
                typeArguments->Length);
            
            for each (Type^ typeArgument in typeArguments)
            {   
                Console::WriteLine("\t\t{0}", typeArgument);
            }
        }
    };
}

int main(void)
{
    Example::Test::CreateConstructedType();
}

/* This example produces the following output:

--- Create a constructed type from the generic Dictionary`2 type.

System.Collections.Generic.Dictionary`2[KeyType,ValueType]
          Is this a generic type definition? True
          Is it a generic type? True
          List type arguments (2):
                     K
                     V

System.Collections.Generic.Dictionary`2[System.String, Test]
          Is this a generic type definition? False
          Is it a generic type? True
          List type arguments (2):
                     System.String
                     Test

--- Compare types obtained by different methods:
          Are the constructed types equal? True
          Are the generic types equal? True
 */

using System;
using System.Reflection;
using System.Collections.Generic;

public class Test
{
    public static void Main()
    {
        Console.WriteLine("\r\n--- Create a constructed type from the generic Dictionary type.");

        // Create a type object representing the generic Dictionary 
        // type, by omitting the type arguments (but keeping the 
        // comma that separates them, so the compiler can infer the
        // number of type parameters).      
        Type generic = typeof(Dictionary<,>);
        DisplayTypeInfo(generic);

        // Create an array of types to substitute for the type
        // parameters of Dictionary. The key is of type string, and
        // the type to be contained in the Dictionary is Test.
        Type[] typeArgs = { typeof(string), typeof(Test) };

        // Create a Type object representing the constructed generic
        // type.
        Type constructed = generic.MakeGenericType(typeArgs);
        DisplayTypeInfo(constructed);

        // Compare the type objects obtained above to type objects
        // obtained using typeof() and GetGenericTypeDefinition().
        Console.WriteLine("\r\n--- Compare types obtained by different methods:");

        Type t = typeof(Dictionary<String, Test>);
        Console.WriteLine("\tAre the constructed types equal? {0}", t == constructed);
        Console.WriteLine("\tAre the generic types equal? {0}", 
            t.GetGenericTypeDefinition() == generic);
    }

    private static void DisplayTypeInfo(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);

        Type[] typeArguments = t.GetGenericArguments();
        Console.WriteLine("\tList type arguments ({0}):", typeArguments.Length);
        foreach (Type tParam in typeArguments)
        {
            Console.WriteLine("\t\t{0}", tParam);
        }
    }
}

/* This example produces the following output:

--- Create a constructed type from the generic Dictionary type.

System.Collections.Generic.Dictionary`2[TKey,TValue]
        Is this a generic type definition? True
        Is it a generic type? True
        List type arguments (2):
                TKey
                TValue

System.Collections.Generic.Dictionary`2[System.String, Test]
        Is this a generic type definition? False
        Is it a generic type? True
        List type arguments (2):
                System.String
                Test

--- Compare types obtained by different methods:
        Are the constructed types equal? True
        Are the generic types equal? True
 */

open System
open System.Collections.Generic

type Test() = class end

let displayTypeInfo (t: Type) =
    printfn $"\r\n{t}"

    printfn $"\tIs this a generic type definition? {t.IsGenericTypeDefinition}" 

    printfn $"\tIs it a generic type? {t.IsGenericType}"

    let typeArguments = t.GetGenericArguments()
    printfn $"\tList type arguments ({typeArguments.Length}):"
    for tParam in typeArguments do
        printfn $"\t\t{tParam}"

printfn "\r\n--- Create a constructed type from the generic Dictionary type."

// Create a type object representing the generic Dictionary 
// type, by calling .GetGenericTypeDefinition().
let generic = typeof<Dictionary<_,_>>.GetGenericTypeDefinition()
displayTypeInfo generic

// Create an array of types to substitute for the type
// parameters of Dictionary. The key is of type string, and
// the type to be contained in the Dictionary is Test.
let typeArgs = [| typeof<string>; typeof<Test> |]

// Create a Type object representing the constructed generic type.
let constructed = generic.MakeGenericType typeArgs
displayTypeInfo constructed

(* This example produces the following output:

--- Create a constructed type from the generic Dictionary type.

System.Collections.Generic.Dictionary`2[TKey,TValue]
        Is this a generic type definition? True
        Is it a generic type? True
        List type arguments (2):
                TKey
                TValue

System.Collections.Generic.Dictionary`2[System.String, Test]
        Is this a generic type definition? False
        Is it a generic type? True
        List type arguments (2):
                System.String
                Test
 *)

Imports System.Reflection
Imports System.Collections.Generic

Public Class Test
    Public Shared Sub Main()
        Console.WriteLine(vbCrLf & "--- Create a constructed type from the generic Dictionary type.")

        ' Create a type object representing the generic Dictionary 
        ' type, by omitting the type arguments (but keeping the 
        ' comma that separates them, so the compiler can infer the
        ' number of type parameters).
        Dim generic As Type = GetType(Dictionary(Of ,))
        DisplayTypeInfo(generic)

        ' Create an array of types to substitute for the type
        ' parameters of Dictionary. The key is of type string, and
        ' the type to be contained in the Dictionary is Test.
        Dim typeArgs() As Type = { GetType(String), GetType(Test) }

        ' Create a Type object representing the constructed generic
        ' type.
        Dim constructed As Type = generic.MakeGenericType(typeArgs)
        DisplayTypeInfo(constructed)

        ' Compare the type objects obtained above to type objects
        ' obtained using GetType() and GetGenericTypeDefinition().
        Console.WriteLine(vbCrLf & "--- Compare types obtained by different methods:")

        Dim t As Type = GetType(Dictionary(Of String, Test))
        Console.WriteLine(vbTab & "Are the constructed types equal? " _
            & (t Is constructed))
        Console.WriteLine(vbTab & "Are the generic types equal? " _ 
            & (t.GetGenericTypeDefinition() Is generic))
    End Sub

    Private Shared Sub DisplayTypeInfo(ByVal t As Type)
        Console.WriteLine(vbCrLf & t.ToString())

        Console.WriteLine(vbTab & "Is this a generic type definition? " _ 
            & t.IsGenericTypeDefinition)

        Console.WriteLine(vbTab & "Is it a generic type? " _ 
            & t.IsGenericType)

        Dim typeArguments() As Type = t.GetGenericArguments()
        Console.WriteLine(vbTab & "List type arguments ({0}):", _
            typeArguments.Length)
        For Each tParam As Type In typeArguments       
            Console.WriteLine(vbTab & vbTab & tParam.ToString())
        Next
    End Sub
End Class

' This example produces the following output:
'
'--- Create a constructed type from the generic Dictionary type.
'
'System.Collections.Generic.Dictionary'2[TKey,TValue]
'        Is this a generic type definition? True
'        Is it a generic type? True
'        List type arguments (2):
'                TKey
'                TValue
'
'System.Collections.Generic.Dictionary`2[System.String,Test]
'        Is this a generic type definition? False
'        Is it a generic type? True
'        List type arguments (2):
'                System.String
'                Test
'
'--- Compare types obtained by different methods:
'        Are the constructed types equal? True
'        Are the generic types equal? True

注解

有关此 API 的详细信息，请参阅 Type.MakeGenericType 的补充 API 备注。

另请参阅

• IsGenericTypeDefinition
• GetGenericTypeDefinition()
• 反射类型和泛型类型
• 如何：使用反射检查和实例化泛型类型