如何在 Activator.CreateInstance 中传递 ctor args 或使用 IL？

Question

我需要一个性能增强的 Activator.CreateInstance() 并遇到 Miron Abramson 的这篇文章，使用工厂在 IL 中创建实例，然后缓存它。 （我在下面添加了来自 Miron Abramson 网站的代码，以防它以某种方式消失）。我对 IL Emit 代码以及用于实例化类的 Activator.CreateInstance() 之外的任何内容都很陌生，任何帮助都将非常感激。

我的问题是我需要创建一个对象的实例，该对象采用带有参数的构造函数。我看到有一种方法可以传入参数的类型，但是有没有一种方法可以传入 ctor 参数的值？

如果可能，我想使用类似于 CreateObjectFactory(params object[] constructorParams) 的方法，因为我想要实例化的某些对象可能有超过 1 个 ctor 参数。

// Source: http://mironabramson.com/blog/post/2008/08/Fast-version-of-the-ActivatorCreateInstance-method-using-IL.aspx
public static class FastObjectFactory
{
    private static readonly Hashtable creatorCache = Hashtable.Synchronized(new Hashtable());
    private readonly static Type coType = typeof(CreateObject);
    public delegate object CreateObject();

    /// 
    /// Create an object that will used as a 'factory' to the specified type T 
   /// 
    public static CreateObject CreateObjectFactory() where T : class
    {
        Type t = typeof(T);
        FastObjectFactory.CreateObject c = creatorCache[t] as FastObjectFactory.CreateObject;
        if (c == null)
        {
            lock (creatorCache.SyncRoot)
            {
                c = creatorCache[t] as FastObjectFactory.CreateObject;
                if (c != null)
                {
                    return c;
                }
                DynamicMethod dynMethod = new DynamicMethod("DM$OBJ_FACTORY_" + t.Name, typeof(object), null, t);
                ILGenerator ilGen = dynMethod.GetILGenerator();

                ilGen.Emit(OpCodes.Newobj, t.GetConstructor(Type.EmptyTypes));
                ilGen.Emit(OpCodes.Ret);
                c = (CreateObject)dynMethod.CreateDelegate(coType);
                creatorCache.Add(t, c);
            }
        }
        return c;
    }
}

更新到 Miron 的代码评论者对其帖子 2010-01-11

public static class FastObjectFactory2<T> where T : class, new()
{
    public static Func<T> CreateObject { get; private set; }

    static FastObjectFactory2()
    {
        Type objType = typeof(T);
        var dynMethod = new DynamicMethod("DM$OBJ_FACTORY_" + objType.Name, objType, null, objType);
        ILGenerator ilGen = dynMethod.GetILGenerator();
        ilGen.Emit(OpCodes.Newobj, objType.GetConstructor(Type.EmptyTypes));
        ilGen.Emit(OpCodes.Ret);
        CreateObject = (Func<T>)
        dynMethod.CreateDelegate(typeof(Func<T>));
    }
}

Answer 1

我一直在对此进行一些测试，并作为 Miron 原始文章的后续内容（此处），我发现 .NET 4.0 Activator 比以前快得多。他的应用程序版本的一些结果经过调整以显示以毫秒为单位的计时：

.NET 3.5 build

Number of iterates: 1000000
Activator.CreateInstance(Type):                           4150
Activator.CreateInstance<T>():                            1288
FastObjectFactory.CreateObjec (empty cache):                33
FastObjectFactory.CreateObjec (cache full):                 28
ItemFactory.GetNewItem:                                   1283


.NET 4.0 build

Number of iterates: 1000000
Activator.CreateInstance(Type):                            138
Activator.CreateInstance<T>():                             151
FastObjectFactory.CreateObjec (empty cache):                28
FastObjectFactory.CreateObjec (cache full):                 22
ItemFactory.GetNewItem:                                    156

然而，这是针对无参数构造函数的，我还注意到，当使用带参数的构造函数时，激活器仍然有点慢，如下所示。

我在此处发布的原始解决方案中遇到的一个问题是，我不一定知道编译时所需的对象的类型 - 我只有一个类型引用。现在（除非我是个笨蛋）这意味着我不能使用这里的通用解决方案或其简单的变体。

所以这是我整理的一个版本，可以解决这个问题。它还显示出使用构造函数参数时 .NET 4.0 Activator 中的轻微缓慢：

// For use with no-parameter constructors. Also contains constants and utility methods
public static class FastActivator
{
    // THIS VERSION NOT THREAD SAFE YET
    static Dictionary<Type, Func<object>> constructorCache = new Dictionary<Type, Func<object>>();

    private const string DynamicMethodPrefix = "DM$_FastActivator_";

    public static object CreateInstance(Type objType)
    {
        return GetConstructor(objType)();
    }

    public static Func<object> GetConstructor(Type objType)
    {
        Func<object> constructor;
        if (!constructorCache.TryGetValue(objType, out constructor))
        {
            constructor = (Func<object>)FastActivator.BuildConstructorDelegate(objType, typeof(Func<object>), new Type[] { });
            constructorCache.Add(objType, constructor);
        }
        return constructor;
    }

    public static object BuildConstructorDelegate(Type objType, Type delegateType, Type[] argTypes)
    {
        var dynMethod = new DynamicMethod(DynamicMethodPrefix + objType.Name + "$" + argTypes.Length.ToString(), objType, argTypes, objType);
        ILGenerator ilGen = dynMethod.GetILGenerator();
        for (int argIdx = 0; argIdx < argTypes.Length; argIdx++)
        {
            ilGen.Emit(OpCodes.Ldarg, argIdx);
        }
        ilGen.Emit(OpCodes.Newobj, objType.GetConstructor(argTypes));
        ilGen.Emit(OpCodes.Ret);
        return dynMethod.CreateDelegate(delegateType);
    }
}

// For use with one-parameter constructors, argument type = T1
public static class FastActivator<T1>
{
    // THIS VERSION NOT THREAD SAFE YET
    static Dictionary<Type, Func<T1, object>> constructorCache = new Dictionary<Type, Func<T1, object>>();
    public static object CreateInstance(Type objType, T1 arg1)
    {
        return GetConstructor(objType, new Type[] { typeof(T1) })(arg1);
    }
    public static Func<T1, object> GetConstructor(Type objType, Type[] argTypes)
    {
        Func<T1, object> constructor;
        if (!constructorCache.TryGetValue(objType, out constructor))
        {
            constructor = (Func<T1, object>)FastActivator.BuildConstructorDelegate(objType, typeof(Func<T1, object>), argTypes);
            constructorCache.Add(objType, constructor);
        }
        return constructor;
    }
}

// For use with two-parameter constructors, argument types = T1, T2
public static class FastActivator<T1, T2>
{
    // THIS VERSION NOT THREAD SAFE YET
    static Dictionary<Type, Func<T1, T2, object>> constructorCache = new Dictionary<Type, Func<T1, T2, object>>();
    public static object CreateInstance(Type objType, T1 arg1, T2 arg2)
    {
        return GetConstructor(objType, new Type[] { typeof(T1), typeof(T2) })(arg1, arg2);
    }

    public static Func<T1, T2, object> GetConstructor(Type objType, Type[] argTypes)
    {
        Func<T1, T2, object> constructor;
        if (!constructorCache.TryGetValue(objType, out constructor))
        {
            constructor = (Func<T1, T2, object>)FastActivator.BuildConstructorDelegate(objType, typeof(Func<T1, T2, object>), argTypes);
            constructorCache.Add(objType, constructor);
        }
        return constructor;
    }
}

// For use with three-parameter constructors, argument types = T1, T2, T3
// NB: could possibly merge these FastActivator<T1,...> classes and avoid generic type parameters
// but would need to take care that cache entries were keyed to distinguish constructors having 
// the same number of parameters but of different types. Keep separate for now.
public static class FastActivator<T1, T2, T3>
{
    // THIS VERSION NOT THREAD SAFE YET
    static Dictionary<Type, Func<T1, T2, T3, object>> constructorCache = new Dictionary<Type, Func<T1, T2, T3, object>>();
    public static object CreateInstance(Type objType, T1 arg1, T2 arg2, T3 arg3)
    {
        return GetConstructor(objType, new Type[] { typeof(T1), typeof(T2), typeof(T3) })(arg1, arg2, arg3);
    }

    public static Func<T1, T2, T3, object> GetConstructor(Type objType, Type[] argTypes)
    {
        Func<T1, T2, T3, object> constructor;
        if (!constructorCache.TryGetValue(objType, out constructor))
        {
            constructor = (Func<T1, T2, T3, object>)FastActivator.BuildConstructorDelegate(objType, typeof(Func<T1, T2, T3, object>), argTypes);
            constructorCache.Add(objType, constructor);
        }
        return constructor;
    }
}

下面是一些性能结果。请注意，这是为了创建 100 万个对象，并且计时再次以毫秒为单位：

Activator.CreateInstance(objType) - parameterless constructor: 153
FastActivator.CreateInstance(objType) - parameterless constructor: 86
Using FastActivator.GetConstructor and calling it repeatedly - parameterless constructor: 34
Activator.CreateInstance(objType) with 1 constructor arg: 3183
FastActivator.CreateInstance(objType) with 1 constructor arg: 257
FastActivator.GetConstructor and calling it repeatedly with 1 constructor arg: 126
Activator.CreateInstance(objType) with 3 constructor args: 4403
FastActivator.CreateInstance(objType) with 3 constructor args: 640
FastActivator.GetConstructor and calling it repeatedly with 3 constructor args : 405
FastActivator.GetConstructor and calling it repeatedly with 3 constructor args; args created only once : 19

Answer 2

根据我的测试，我将其作为迄今为止使用当前（2010-01-11）答案的最佳性能对象创建工厂。我确实注意到，当迭代次数低于 99,999 时，使用缓存效果最佳。如果要加载超过 99,999 个，最好不要使用缓存。因为可能是这种情况，所以我创建了一些允许您使用缓存或不使用缓存的东西。我当前的项目有时会加载数百万条记录，有时只加载一条记录。不管怎样，我把这个放在那里看看你的想法是什么。请注意，下面的代码适用于具有 1 个参数的 ctor，因此必须为超过 1 个参数的 ctor 创建一个类似的工厂。

// code updated 2010-06-01
// class that creates comment objects
public class CreatesSomeObject
{
    // method that creates a comment object
    public void CreateComment()
    {

        // Method 1 (without cache)
        Comment comment1 = ObjectFactoryFactory<Comment, ObjectId>
            .CreateObject.Invoke(new ObjectId());

        // Method 2 (with cache)
        Comment comment2 = ObjectFactoryFactory<Comment, ObjectId>
            .CreateObjectWithCache.Invoke(new ObjectId());

        // Method 3 (without helper factory ObjectFactoryFactory)
        Comment comment3 = ObjectFactory<Comment, ObjectId>
            .CreateObject.Invoke(new ObjectId());
    }
}

// This is optional class. Just helps in creating objects when
// a cache is needed or not needed.
public static class ObjectFactoryFactory<T, P1> where T : class
{
    static Hashtable cache = Hashtable.Synchronized(new Hashtable());

    public static Func<P1, T> CreateObject
    {
        get { return ObjectFactory<T, P1>.CreateObject; }
    }

    public static Func<P1, T> CreateObjectWithCache
    {
        get
        {
            return ObjectFactory<T, P1>.UseCache(cache);
        }
    }
}

// Main object creation factory class.
public static class ObjectFactory<T, P1> where T : class
{

    static Func<P1, T> _createObject;

    public static Func<P1, T> CreateObject
    {
        get
        {
            if (_createObject != null) return _createObject;
            _createObject = CreateDelegate();
            return _createObject;
        }
    }

    static Func<P1, T> CreateDelegate()
    {
        Type objType = typeof(T);
        Type[] types = new[] { typeof(P1) };
        var dynMethod = new DynamicMethod("DM$OBJ_FACTORY_" + 
            objType.Name, objType, types, objType);
        ILGenerator ilGen = dynMethod.GetILGenerator();
        // if need more than 1 arg add another Ldarg_x
        // you'll also need to add proper generics and 
        // CreateDelegate signatures
        ilGen.Emit(OpCodes.Ldarg_0);
        ilGen.Emit(OpCodes.Newobj, objType.GetConstructor(types));
        ilGen.Emit(OpCodes.Ret);
        return (Func<P1, T>)dynMethod.CreateDelegate(typeof(Func<P1, T>));
    }

    public static Func<P1, T> UseCache(Hashtable cache) 
    { 
        Type t = typeof(T);
        Func<P1, T> c = cache[t] as Func<P1, T>;
        if (c == null) 
        { 
            lock (cache.SyncRoot) 
            {
                c = cache[t] as Func<P1, T>;
                if (c != null) 
                { 
                    return c; 
                } 
                c = CreateDelegate(); 
                cache.Add(t, c); 
            } 

        } 
        return c; 
    }
}

Answer 3

我不久前写过这个。它使用 .NET 3.5 Linq Expression 树而不是发出 IL，这几乎同样快且更易于维护。它最多可以使用 4 个构造函数参数。

像您想要的那样使用任何构造函数参数可能会慢一点，因为根据参数类型查找构造函数，但它仍然比使用反射快得多。我认为，对于 IL 发射，还必须进行一些查找。

您必须指定要构造的确切类型，因为它不是 IOC/DI 容器。也许您可以根据您的需要扩展和调整它。

// usage:
Cat myCat = Instantiator<Cat>.New("furry", /* isCute*/ true);

using System;
using System.Diagnostics;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;

static public class Instantiator<TInstance>
{
    static Instantiator()
    {
        Debug.Assert(typeof(TInstance).IsValueType || (typeof(TInstance).IsClass && !typeof(TInstance).IsAbstract),
                String.Concat("The type ", typeof(TInstance).Name, " is not constructable."));
    }

    static public TInstance New()
    {
        return InstantiatorImpl.CtorFunc();
    }

    static public TInstance New<TA>(TA valueA)
    {
        return InstantiatorImpl<TA>.CtorFunc(valueA);
    }

    static public TInstance New<TA, TB>(TA valueA, TB valueB)
    {
        return InstantiatorImpl<TA, TB>.CtorFunc(valueA, valueB);
    }

    static public TInstance New<TA, TB, TC>(TA valueA, TB valueB, TC valueC)
    {
        return InstantiatorImpl<TA, TB, TC>.CtorFunc(valueA, valueB, valueC);
    }

    static public TInstance New<TA, TB, TC, TD>(TA valueA, TB valueB, TC valueC, TD valueD)
    {
        return InstantiatorImpl<TA, TB, TC, TD>.CtorFunc(valueA, valueB, valueC, valueD);
    }

    static private Expression<TDelegate> CreateLambdaExpression<TDelegate>(params Type[] argTypes)
    {
        Debug.Assert(argTypes != null);

        ParameterExpression[] paramExpressions = new ParameterExpression[argTypes.Length];

        for (int i = 0; i < paramExpressions.Length; i++)
        {
            paramExpressions[i] = Expression.Parameter(argTypes[i], String.Concat("arg", i));
        }

        ConstructorInfo ctorInfo = typeof(TInstance).GetConstructor(argTypes);
        if (ctorInfo == null)
        {
            throw new ArgumentException(String.Concat("The type ", typeof(TInstance).Name, " has no constructor with the argument type(s) ", String.Join(", ", argTypes.Select(t => t.Name).ToArray()), "."),
                    "argTypes");
        }

        return Expression.Lambda<TDelegate>(Expression.New(ctorInfo, paramExpressions), paramExpressions);
    }

    static private class InstantiatorImpl
    {
        static public readonly Func<TInstance> CtorFunc = Expression.Lambda<Func<TInstance>>(Expression.New(typeof(TInstance))).Compile();
    }

    static private class InstantiatorImpl<TA>
    {
        static public readonly Func<TA, TInstance> CtorFunc = Instantiator<TInstance>.CreateLambdaExpression<Func<TA, TInstance>>(typeof(TA)).Compile();
    }

    static private class InstantiatorImpl<TA, TB>
    {
        static public readonly Func<TA, TB, TInstance> CtorFunc = Instantiator<TInstance>.CreateLambdaExpression<Func<TA, TB, TInstance>>(typeof(TA), typeof(TB)).Compile();
    }

    static private class InstantiatorImpl<TA, TB, TC>
    {
        static public readonly Func<TA, TB, TC, TInstance> CtorFunc = Instantiator<TInstance>.CreateLambdaExpression<Func<TA, TB, TC, TInstance>>(typeof(TA), typeof(TB), typeof(TC)).Compile();
    }

    static private class InstantiatorImpl<TA, TB, TC, TD>
    {
        static public readonly Func<TA, TB, TC, TD, TInstance> CtorFunc = Instantiator<TInstance>.CreateLambdaExpression<Func<TA, TB, TC, TD, TInstance>>(typeof(TA), typeof(TB), typeof(TC), typeof(TD)).Compile();
    }
}

尽情享受吧！ :->

Answer 4

我不知道 new T() 在泛型类中很慢。我的问题确实是别的问题 - 如果我知道 T 在编译时是什么，那就没问题了，但我想要一种快速的方法来实例化运行时由配置信息（即包含程序集/类名称的字符串）指定的类。我使用 Type 对象的缓存来加载程序集并仅在其中定位类型一次，因此最后一个障碍是快速创建实例，这是我上一篇文章的主题。

不管怎样，根据我的发现，.NET 4.0 在这类事情上更快，我用你的示例版本进行了测试，调用每个 CreateNewInstxxx 方法 1,000,000 次。计时以毫秒为单位：

class GenericClass<T> where T : new()
{
    Func<T> ClassFactory;    
    public GenericClass(Func<T> classFactory)    
    {        
        this.ClassFactory = classFactory;    
    }    
    public T CreateNewInstQuick()    
    {        
        return ClassFactory(); // Calls the quick IL mnemonic 'newobj'   
    }
    public T CreateNewInstStd()
    {
        return new T(); // <- calls the slow Activator.CreateInstance() in IL
    }
}

.NET 3.5
CreateNewInstQuick: 35
CreateNewInstStd: 1298

.NET 4.0
CreateNewInstQuick: 29
CreateNewInstStd: 165

所以，是的，.NET 4.0 也比以前快得多。编译器为 CreateNewInstStd() 方法生成的代码在这两种情况下看起来都是这样，因此速度似乎取决于改进的 Activator.CreateInstance() 方法：

public T CreateNewInstStd()
{
    T t1 = default(T);
    if (t1 != null)
    {
        T t2 = default(T);
        return t2;
    }
    return Activator.CreateInstance<T>();
}

编辑：添加当 GenericClass 通过以下方式限制为引用类型时，性能大致相同：

class GenericClass<T> where T :  class, new()

在这种情况下，编译器生成的代码就是这样：

public T CreateNewInstStd()
{
    return Activator.CreateInstance<T>();
}

Answer 5

我通常使用以下方法来完全避免泛型类中的Activator.CreateInstance()。

我需要将 Func 委托传递给构造函数。如果需要实例化 T 的新实例，该类将调用此方法。这将使实例化与非泛型类一样快，并且在我看来比发出 IL 的复杂类更简单、更优雅。使用此方法时的另一个好处（VS New T()）是您可以使用参数化构造函数实例化一个类。

编辑：我已根据 BillW 的请求使用参数化构造函数示例更新了代码。

class GenericClass<T>
{
    public GenericClass(Func<T> classFactory)
    {
        this.ClassFactory = classFactory;
    }
    Func<T> ClassFactory;

    public void CreateNewInstDemo()
    {
        //T NewObject = New T(); // <- calls the slow Activator.CreateInstance() in IL
        T NewObject = ClassFactory(); // Calls the quick IL mnemonic 'newobj'
    }
}
class GenericClassParamsDemo<T>
{
    public GenericClassParamsDemo(Func<int, T> classFactory)
    {
        this.ClassFactory = classFactory;
    }
    Func<int, T> ClassFactory;

    public void CreateNewInstDemo()
    {
        T NewObject = ClassFactory(5); // Calls the quick IL mnemonic 'newobj'
    }
}
class ClassToCreate
{
    public int Number { get; set; }
    public ClassToCreate()
    {
        // Default constructor
    }
    public ClassToCreate(int number)
    {
        // Constructor With Parameter
        this.Number = number;
    }
}
class Program
{
    static void Main(string[] args)
    {
        GenericClass<ClassToCreate> gc =
        new GenericClass<ClassToCreate>(() => { return new ClassToCreate(); });
        // Call method which uses delegate to create a new instance
        gc.CreateNewInstDemo();

        GenericClassParamsDemo<ClassToCreate> gcParams =
        new GenericClassParamsDemo<ClassToCreate>((number) => { return new ClassToCreate(number); });
         // Call method which uses delegate to create a new instance with params
        gcParams.CreateNewInstDemo();
    }
}

Answer 6

如果您不使用简单的方法，您的探查器是否向您显示大量时间花费在 Activator.CreateInstance() （而不是它调用的任何构造函数）上。如果不是这种情况，只需使用 Activator.CreateInstance。 （似乎没有带有 ctor 参数的通用 CreateInstance() 方法，但有一个非通用方法）。

Answer 7

接下来是将 @thames 答案转换为 VB.NET。

//' Original source: http://stackoverflow.com/questions/2024435/how-to-pass-ctor-args-in-activator-createinstance-or-use-il/2045313#2045313
//' Converted to VB with: http://www.developerfusion.com/tools/convert/csharp-to-vb/
//' code updated 2010-06-01
//' class that creates comment objects
Public Class CreatesSomeObject

    //' method that creates a comment object
    Public Sub CreateComment()

        //' Method 1 (without cache)
        Dim comment1 As Comment = ObjectFactoryFactory(Of Comment, ObjectId).CreateObject.Invoke(New ObjectId())

        //' Method 2 (with cache)
        Dim comment2 As Comment = ObjectFactoryFactory(Of Comment, ObjectId).CreateObjectWithCache.Invoke(New ObjectId())

        //' Method 3 (without helper factory ObjectFactoryFactory)
        Dim comment3 As Comment = ObjectFactory(Of Comment, ObjectId).CreateObject.Invoke(New ObjectId())

    End Sub

End Class

Public Class Comment

    Public Sub New(ByVal objectId As ObjectId)
    End Sub

End Class

Public Class ObjectId
End Class

//' This is optional class. Just helps in creating objects when
//' a cache is needed or not needed.
Public NotInheritable Class ObjectFactoryFactory(Of T As Class, P1)

    Private Sub New()
    End Sub

    Shared cache As Hashtable = Hashtable.Synchronized(New Hashtable())

    Public Shared ReadOnly Property CreateObject() As Func(Of P1, T)
        Get
            Return ObjectFactory(Of T, P1).CreateObject
        End Get
    End Property

    Public Shared ReadOnly Property CreateObjectWithCache() As Func(Of P1, T)
        Get
            Return ObjectFactory(Of T, P1).UseCache(cache)
        End Get
    End Property
End Class

//' Main object creation factory class.
Public NotInheritable Class ObjectFactory(Of T As Class, P1)

    Private Sub New()
    End Sub

    Shared _createObject As Func(Of P1, T)

    Public Shared ReadOnly Property CreateObject() As Func(Of P1, T)
        Get
            If _createObject IsNot Nothing Then
                Return _createObject
            End If
            _createObject = CreateDelegate()
            Return _createObject
        End Get
    End Property

    Private Shared Function CreateDelegate() As Func(Of P1, T)

        Dim objType As Type = GetType(T)
        Dim types As Type() = {GetType(P1)}
        Dim dynMethod = New DynamicMethod("DM$OBJ_FACTORY_" + objType.Name, objType, types, objType)
        Dim ilGen As ILGenerator = dynMethod.GetILGenerator()

        //' if need more than 1 arg add another Ldarg_x
        //' you'll also need to add proper generics and 
        //' CreateDelegate signatures
        ilGen.Emit(OpCodes.Ldarg_0)
        ilGen.Emit(OpCodes.Newobj, objType.GetConstructor(types))
        ilGen.Emit(OpCodes.Ret)

        Return DirectCast(dynMethod.CreateDelegate(GetType(Func(Of P1, T))), Func(Of P1, T))

    End Function

    Public Shared Function UseCache(ByVal cache As Hashtable) As Func(Of P1, T)

        Dim t As Type = GetType(T)
        Dim c As Func(Of P1, T) = TryCast(cache(t), Func(Of P1, T))

        If c Is Nothing Then

            SyncLock cache.SyncRoot

                c = TryCast(cache(t), Func(Of P1, T))
                If c IsNot Nothing Then
                    Return c
                End If
                c = CreateDelegate()
                cache.Add(t, c)

            End SyncLock

        End If

        Return c

    End Function

End Class

请注意，使用 //' 进行注释可以使代码着色器正常工作。将此代码粘贴到您的项目中后，将 //' 替换为 '.

Answer 8

我认为您需要更改的第一件事是 CreateObject 委托。我会这样做：

public delegate object CreateObject(params object[] args);

然后，这是从 ConstructorInfo 生成 CreateObject 委托的好方法（使用表达式树）：

/// <summary>
///    Creates and compiles an Expression like this:
/// (object[] args) =>
/// (object)(
///     new {ConstructedType}(args[0], args[1], ...)
/// )
/// </summary>
public static DynamicStaticMethod CreateConstructor(ConstructorInfo constructor)
{
    if (constructor == null) throw new ArgumentNullException("constructor");

    //Create 'args' parameter expression
    ParameterExpression argsParameter = Expression.Parameter(typeof(object[]), "args");

    //Create body expression
    ParameterInfo[] constructorParams = constructor.GetParameters();
    Expression body = Expression.New(
        constructor,
        CreateParameterExpressions(constructorParams, argsParameter)
    );

    //Create and compile lambda
    var lambda = Expression.Lambda<CreateObject>(
        Expression.Convert(body, typeof(object)),
        argsParameter
    );
    return lambda.Compile();
}

该编译器的完整扩展版本位于我的个人存储库。随意浏览那里的任何内容。

更新：存储库链接已更改。