TypeBuilder.GetConstructor(Type, ConstructorInfo) 方法

定义

命名空间:

System.Reflection.Emit

程序集:

System.Reflection.Emit.dll

Source:

RuntimeTypeBuilder.cs

返回与指定泛型类型定义的构造函数相对应的指定构造泛型类型的构造函数。

public:
 static System::Reflection::ConstructorInfo ^ GetConstructor(Type ^ type, System::Reflection::ConstructorInfo ^ constructor);

public static System.Reflection.ConstructorInfo GetConstructor (Type type, System.Reflection.ConstructorInfo constructor);

static member GetConstructor : Type * System.Reflection.ConstructorInfo -> System.Reflection.ConstructorInfo

Public Shared Function GetConstructor (type As Type, constructor As ConstructorInfo) As ConstructorInfo

参数

type

Type

已返回其构造函数的构造泛型类型。

constructor

ConstructorInfo

基于 type 的泛型类型定义的构造函数，该函数指定要返回 type 的哪个构造函数

返回

ConstructorInfo

ConstructorInfo 对象，它表示与 constructor 对应的 type 的构造函数，它指定属于 type 的泛型类型定义的构造函数 。

例外

ArgumentException

type 不表示泛型类型。

- 或 -

type 的类型不是 TypeBuilder。

- 或 -

constructor 的声明类型不是一个泛型类型定义。

- 或 -

constructor 的声明类型不是 type 的泛型类型定义。

示例

下面的代码示例包含名为 Sample 的泛型类的源代码，该类具有名为 的类型 T参数。 类有一个名为 Field的字段，类型 T为 ，以及一个名为 的 GM 泛型方法，其自己的类型参数名为 U。 方法 GM 创建 的 Sample实例，将自己的类型参数 U 替换为 的类型 Sample参数，并将其输入参数存储在 中 Field。 此源代码已编译，但未使用;可以使用 Ildasm.exe (IL 反汇编程序) 查看它，并将其与类 Example发出的代码进行比较。

类 Example 中的代码演示如何使用 GetConstructor 方法发出泛型代码。 Main类Example的 方法创建包含名为 Sample 的类的动态程序集，DefineGenericParameters并使用 方法通过添加名为 的类型参数使其成为泛型T。 无参数构造函数和类型 Field为 的 T字段添加到类 Sample。 使用 MethodBuilder.DefineGenericParameters 方法GM添加方法并将其转换为泛型方法。 的 GM 类型参数名为 U。 定义类型参数后，使用 MethodBuilder.SetSignature 方法添加 的GM签名。 没有返回类型，也没有必需的或自定义修饰符，因此此方法的所有参数都 null 除外 parameterTypes; parameterTypes 将方法唯一参数的类型设置为 U方法的泛型类型参数。 方法的主体在 Visual Basic) 中创建构造类型的 Sample<U> 实例 (Sample(Of U) ，将方法的参数 Field分配给 ，然后打印 的值 Field。 方法GetConstructor用于在创建实例的指令中创建OpCodes.Newobj一个 ConstructorInfo ，它表示构造的泛型类型的Sample<U>无参数构造函数。

将虚拟类型定义为保存入口点方法 Main。 在 的 Main主体中， GM 静态方法在 Visual Basic) 中构造的泛型类型 Sample<int> (Sample(Of Integer) 上调用，类型 String 替换为 U。

运行代码示例时，它会将发出的程序集保存为 TypeBuilderGetFieldExample.exe。 可以运行 TypeBuilderGetFieldExample.exe，并且可以使用 Ildasm.exe (IL 反汇编程序) 将发出的代码与编译为代码示例本身的类的代码 Sample 进行比较。

using System;
using System.Reflection;
using System.Reflection.Emit;

// Compare the MSIL in this class to the MSIL
// generated by the Reflection.Emit code in class
// Example.
public class Sample<T>
{
  public T Field;
  public static void GM<U>(U val)
  {
    Sample<U> s = new Sample<U>();
    s.Field = val;
    Console.WriteLine(s.Field);
  }
}

public class Example
{
    public static void Main()
    {
        AppDomain myDomain = AppDomain.CurrentDomain;
        AssemblyName myAsmName =
            new AssemblyName("TypeBuilderGetFieldExample");
        AssemblyBuilder myAssembly = myDomain.DefineDynamicAssembly(
            myAsmName, AssemblyBuilderAccess.Save);
        ModuleBuilder myModule = myAssembly.DefineDynamicModule(
            myAsmName.Name,
            myAsmName.Name + ".exe");

        // Define the sample type.
        TypeBuilder myType = myModule.DefineType("Sample",
            TypeAttributes.Class | TypeAttributes.Public);

        // Add a type parameter, making the type generic.
        string[] typeParamNames = {"T"};
        GenericTypeParameterBuilder[] typeParams =
            myType.DefineGenericParameters(typeParamNames);

        // Define a default constructor. Normally it would
        // not be necessary to define the default constructor,
        // but in this case it is needed for the call to
        // TypeBuilder.GetConstructor, which gets the default
        // constructor for the generic type constructed from
        // Sample<T>, in the generic method GM<U>.
        ConstructorBuilder ctor = myType.DefineDefaultConstructor(
            MethodAttributes.PrivateScope | MethodAttributes.Public |
            MethodAttributes.HideBySig | MethodAttributes.SpecialName |
            MethodAttributes.RTSpecialName);

        // Add a field of type T, with the name Field.
        FieldBuilder myField = myType.DefineField("Field",
            typeParams[0],
            FieldAttributes.Public);

        // Add a method and make it generic, with a type
        // parameter named U. Note how similar this is to
        // the way Sample is turned into a generic type. The
        // method has no signature, because the type of its
        // only parameter is U, which is not yet defined.
        MethodBuilder genMethod = myType.DefineMethod("GM",
            MethodAttributes.Public | MethodAttributes.Static);
        string[] methodParamNames = {"U"};
        GenericTypeParameterBuilder[] methodParams =
            genMethod.DefineGenericParameters(methodParamNames);

        // Now add a signature for genMethod, specifying U
        // as the type of the parameter. There is no return value
        // and no custom modifiers.
        genMethod.SetSignature(null, null, null,
            new Type[] { methodParams[0] }, null, null);

        // Emit a method body for the generic method.
        ILGenerator ilg = genMethod.GetILGenerator();
        // Construct the type Sample<U> using MakeGenericType.
        Type SampleOfU = myType.MakeGenericType( methodParams[0] );
        // Create a local variable to store the instance of
        // Sample<U>.
        ilg.DeclareLocal(SampleOfU);
        // Call the default constructor. Note that it is
        // necessary to have the default constructor for the
        // constructed generic type Sample<U>; use the
        // TypeBuilder.GetConstructor method to obtain this
        // constructor.
        ConstructorInfo ctorOfU = TypeBuilder.GetConstructor(
            SampleOfU, ctor);
        ilg.Emit(OpCodes.Newobj, ctorOfU);
        // Store the instance in the local variable; load it
        // again, and load the parameter of genMethod.
        ilg.Emit(OpCodes.Stloc_0);
        ilg.Emit(OpCodes.Ldloc_0);
        ilg.Emit(OpCodes.Ldarg_0);
        // In order to store the value in the field of the
        // instance of Sample<U>, it is necessary to have
        // a FieldInfo representing the field of the
        // constructed type. Use TypeBuilder.GetField to
        // obtain this FieldInfo.
        FieldInfo FieldOfU = TypeBuilder.GetField(
            SampleOfU, myField);
        // Store the value in the field.
        ilg.Emit(OpCodes.Stfld, FieldOfU);
        // Load the instance, load the field value, box it
        // (specifying the type of the type parameter, U), and
        // print it.
        ilg.Emit(OpCodes.Ldloc_0);
        ilg.Emit(OpCodes.Ldfld, FieldOfU);
        ilg.Emit(OpCodes.Box, methodParams[0]);
        MethodInfo writeLineObj =
            typeof(Console).GetMethod("WriteLine",
                new Type[] { typeof(object) });
        ilg.EmitCall(OpCodes.Call, writeLineObj, null);
        ilg.Emit(OpCodes.Ret);

        // Emit an entry point method; this must be in a
        // non-generic type.
        TypeBuilder dummy = myModule.DefineType("Dummy",
            TypeAttributes.Class | TypeAttributes.NotPublic);
        MethodBuilder entryPoint = dummy.DefineMethod("Main",
            MethodAttributes.Public | MethodAttributes.Static,
            null, null);
        ilg = entryPoint.GetILGenerator();
        // In order to call the static generic method GM, it is
        // necessary to create a constructed type from the
        // generic type definition for Sample. This can be any
        // constructed type; in this case Sample<int> is used.
        Type SampleOfInt =
            myType.MakeGenericType( typeof(int) );
        // Next get a MethodInfo representing the static generic
        // method GM on type Sample<int>.
        MethodInfo SampleOfIntGM = TypeBuilder.GetMethod(SampleOfInt,
            genMethod);
        // Next get a MethodInfo for GM<string>, which is the
        // instantiation of GM that Main calls.
        MethodInfo GMOfString =
            SampleOfIntGM.MakeGenericMethod( typeof(string) );
        // Finally, emit the call. Push a string onto
        // the stack, as the argument for the generic method.
        ilg.Emit(OpCodes.Ldstr, "Hello, world!");
        ilg.EmitCall(OpCodes.Call, GMOfString, null);
        ilg.Emit(OpCodes.Ret);

        myType.CreateType();
        dummy.CreateType();
        myAssembly.SetEntryPoint(entryPoint);
        myAssembly.Save(myAsmName.Name + ".exe");

        Console.WriteLine(myAsmName.Name + ".exe has been saved.");
    }
}

Imports System.Reflection
Imports System.Reflection.Emit

' Compare the MSIL in this class to the MSIL
' generated by the Reflection.Emit code in class
' Example.
Public Class Sample(Of T)
    Public Field As T
    Public Shared Sub GM(Of U)(ByVal val As U)
        Dim s As New Sample(Of U)
        s.Field = val
        Console.WriteLine(s.Field)
    
    End Sub
End Class 

Public Class Example
    
    Public Shared Sub Main() 
        Dim myDomain As AppDomain = AppDomain.CurrentDomain
        Dim myAsmName As New AssemblyName("TypeBuilderGetFieldExample")
        Dim myAssembly As AssemblyBuilder = _
            myDomain.DefineDynamicAssembly(myAsmName, _
                AssemblyBuilderAccess.Save)
        Dim myModule As ModuleBuilder = _
            myAssembly.DefineDynamicModule(myAsmName.Name, _
                myAsmName.Name & ".exe")
        
        ' Define the sample type.
        Dim myType As TypeBuilder = myModule.DefineType( _
            "Sample", _
            TypeAttributes.Class Or TypeAttributes.Public)
        
        ' Add a type parameter, making the type generic.
        Dim typeParamNames() As String = { "T" }
        Dim typeParams As GenericTypeParameterBuilder() = _
            myType.DefineGenericParameters(typeParamNames)
        
        ' Define a default constructor. Normally it would 
        ' not be necessary to define the default constructor,
        ' but in this case it is needed for the call to
        ' TypeBuilder.GetConstructor, which gets the default
        ' constructor for the generic type constructed from 
        ' Sample(Of T), in the generic method GM(Of U).
        Dim ctor As ConstructorBuilder = _
            myType.DefineDefaultConstructor( _
                MethodAttributes.PrivateScope Or MethodAttributes.Public _
                Or MethodAttributes.HideBySig Or MethodAttributes.SpecialName _
                Or MethodAttributes.RTSpecialName)
        
        ' Add a field of type T, with the name Field.
        Dim myField As FieldBuilder = myType.DefineField( _
            "Field", typeParams(0), FieldAttributes.Public)
        
        ' Add a method and make it generic, with a type 
        ' parameter named U. Note how similar this is to 
        ' the way Sample is turned into a generic type. The
        ' method has no signature, because the type of its
        ' only parameter is U, which is not yet defined.
        Dim genMethod As MethodBuilder = _
            myType.DefineMethod("GM", _
                MethodAttributes.Public Or MethodAttributes.Static)
        Dim methodParamNames() As String = { "U" }
        Dim methodParams As GenericTypeParameterBuilder() = _
            genMethod.DefineGenericParameters(methodParamNames)

        ' Now add a signature for genMethod, specifying U
        ' as the type of the parameter. There is no return value
        ' and no custom modifiers.
        genMethod.SetSignature(Nothing, Nothing, Nothing, _
            New Type() { methodParams(0) }, Nothing, Nothing)
        
        ' Emit a method body for the generic method.
        Dim ilg As ILGenerator = genMethod.GetILGenerator()
        ' Construct the type Sample(Of U) using MakeGenericType.
        Dim SampleOfU As Type = _
            myType.MakeGenericType(methodParams(0))
        ' Create a local variable to store the instance of
        ' Sample(Of U).
        ilg.DeclareLocal(SampleOfU)
        ' Call the default constructor. Note that it is 
        ' necessary to have the default constructor for the
        ' constructed generic type Sample(Of U); use the 
        ' TypeBuilder.GetConstructor method to obtain this 
        ' constructor.
        Dim ctorOfU As ConstructorInfo = _
            TypeBuilder.GetConstructor(SampleOfU, ctor)
        ilg.Emit(OpCodes.Newobj, ctorOfU)
        ' Store the instance in the local variable; load it
        ' again, and load the parameter of genMethod.
        ilg.Emit(OpCodes.Stloc_0)
        ilg.Emit(OpCodes.Ldloc_0)
        ilg.Emit(OpCodes.Ldarg_0)
        ' In order to store the value in the field of the
        ' instance of Sample(Of U), it is necessary to have 
        ' a FieldInfo representing the field of the 
        ' constructed type. Use TypeBuilder.GetField to 
        ' obtain this FieldInfo.
        Dim FieldOfU As FieldInfo = _
            TypeBuilder.GetField(SampleOfU, myField)
        ' Store the value in the field. 
        ilg.Emit(OpCodes.Stfld, FieldOfU)
        ' Load the instance, load the field value, box it
        ' (specifying the type of the type parameter, U), 
        ' and print it.
        ilg.Emit(OpCodes.Ldloc_0)
        ilg.Emit(OpCodes.Ldfld, FieldOfU)
        ilg.Emit(OpCodes.Box, methodParams(0))
        Dim writeLineObj As MethodInfo = _
            GetType(Console).GetMethod("WriteLine", _
                New Type() {GetType(Object)})
        ilg.EmitCall(OpCodes.Call, writeLineObj, Nothing)
        ilg.Emit(OpCodes.Ret)
        
        ' Emit an entry point method; this must be in a
        ' non-generic type.
        Dim dummy As TypeBuilder = _
            myModule.DefineType("Dummy", _
                TypeAttributes.Class Or TypeAttributes.NotPublic)
        Dim entryPoint As MethodBuilder = _
            dummy.DefineMethod("Main", _
                MethodAttributes.Public Or MethodAttributes.Static, _
                Nothing, Nothing)
        ilg = entryPoint.GetILGenerator()
        ' In order to call the static generic method GM, it is
        ' necessary to create a constructed type from the 
        ' generic type definition for Sample. This can be ANY
        ' constructed type; in this case Sample(Of Integer)
        ' is used.
        Dim SampleOfInt As Type = _
            myType.MakeGenericType(GetType(Integer))
        ' Next get a MethodInfo representing the static generic
        ' method GM on type Sample(Of Integer).
        Dim SampleOfIntGM As MethodInfo = _
            TypeBuilder.GetMethod(SampleOfInt, genMethod)
        ' Next get a MethodInfo for GM(Of String), which is the 
        ' instantiation of generic method GM that is called
        ' by Sub Main.
        Dim GMOfString As MethodInfo = _
            SampleOfIntGM.MakeGenericMethod(GetType(String))
        ' Finally, emit the call. Push a string onto
        ' the stack, as the argument for the generic method.
        ilg.Emit(OpCodes.Ldstr, "Hello, world!")
        ilg.EmitCall(OpCodes.Call, GMOfString, Nothing)
        ilg.Emit(OpCodes.Ret)
        
        myType.CreateType()
        dummy.CreateType()
        myAssembly.SetEntryPoint(entryPoint)
        myAssembly.Save(myAsmName.Name & ".exe")
        
        Console.WriteLine(myAsmName.Name & ".exe has been saved.")
    
    End Sub 
End Class

注解

方法 GetConstructor 提供了一 ConstructorInfo 种获取 对象的方法，该对象表示构造的泛型类型的构造函数，其泛型类型定义由 TypeBuilder 对象表示。

例如，假设你有一个 TypeBuilder 对象，该对象表示 Visual Basic generic <T> ref class G 中 C# 语法 (G(Of T)、G<T>C++) 中的 类型，以及一个 ConstructorBuilder 表示 构造函数的对象G<T>。 G<T>假设 具有一个泛型方法，其中包含类型参数U，用于创建构造类型 G<U>的实例。 若要发出代码以创建构造类型的实例，需要一个 ConstructorInfo 对象来表示此构造类型的构造函数 （换句话说，该对象创建 的 G<U>实例）。 为此，请首先对 TypeBuilder 对象调用 MakeGenericType 方法，并GenericTypeParameterBuilder指定表示U为类型参数的对象。 然后， GetConstructor 使用 方法的 MakeGenericType 返回值作为参数 type 调用 方法， ConstructorBuilder 并将 表示 的构造函数 G<U> 的 对象作为参数 constructor调用 。 返回值是 ConstructorInfo 发出函数调用所需的对象。 代码示例演示了此方案。