带参数的 C# 反射发出调用

Question

我想用 reflection.emit API 参数调用一个函数。以下是我目前所拥有的。但是当我运行它时，它会抛出以下异常：System.InvalidProgramException : Common Language Runtime detected an invalid program。所以我的问题是我下面的代码片段有什么问题？有人可以帮我吗？

public class Test
{

    public void test()
    {
        Func<int, long> realSquareFunc = (val) => val * val;
        Type[] methodArgs = { typeof(int) };

        DynamicMethod squareIt = new DynamicMethod(
            "SquareIt",
            typeof(long),
            methodArgs,
            typeof(Test).Module)
        ;

        ILGenerator il = squareIt.GetILGenerator();
        il.Emit(OpCodes.Ldarg_0); // Save parameter on stack
        il.Emit(OpCodes.Call, realSquareFunc.Method); // Call function with input as parameter
        il.Emit(OpCodes.Ret); // Return value from function call before

        var myMethod = (Func<int, long>)squareIt.CreateDelegate(realSquareFunc.GetType());
        var result = myMethod.Invoke(4); // Should be 16 (4*4)
    }

}

Answer 1

如果调用的方法是静态方法，您的代码将按原样运行：

public static long RealSquare(int val) => val * val;

public void test()
{
    Func<int, long> realSquareFunc = RealSquare;
    // ...

然而，realSquareFunc = (val) => val * val lambda 实际上被编译为隐藏class 的实例方法。要调用实例方法，必须先将实例压入堆栈，然后再压入方法参数。实例方法调用通常也使用 Callvirt 操作码（不管它们是否是虚拟的，因为此操作码会进行空引用检查）：

public class Test
{
    public long RealSquare(int val) => val * val;

    public void test()
    {
        Func<int, long> realSquareFunc = RealSquare;
        // pass the instance we want to call the method on in as well
        Type[] methodArgs = { typeof(Test), typeof(int) };

        DynamicMethod squareIt = new DynamicMethod(
            "SquareIt",
            typeof(long),
            methodArgs,
            typeof(Test).Module)
        ;

        ILGenerator il = squareIt.GetILGenerator();
        il.Emit(OpCodes.Ldarg_0); // Push the target instance onto stack      
        il.Emit(OpCodes.Ldarg_1); // Save parameter on stack
        il.Emit(OpCodes.Callvirt, realSquareFunc.Method); // Call function with input as parameter
        il.Emit(OpCodes.Ret); // Return value from function call before

        var myMethod = (Func<Test, int, long>)squareIt.CreateDelegate(typeof(Func<Test, int, long>));
        var result = myMethod.Invoke(this, 4); // Should be 16 (4*4)
    }  
}

直接调用 lambda 的目标方法由于涉及编译器生成的 class 更复杂，但是如果你想调用一般的委托它像这样工作：

public class Test
{        
    public void test()
    {
        Func<int, long> realSquareFunc = (val) => val * val;
        // pass the delegate we want to call into the method
        Type[] methodArgs = { realSquareFunc.GetType(), typeof(int) };

        DynamicMethod squareIt = new DynamicMethod(
            "SquareIt",
            typeof(long),
            methodArgs,
            typeof(Test).Module)
        ;

        ILGenerator il = squareIt.GetILGenerator();
        il.Emit(OpCodes.Ldarg_0); // Push the delegate onto stack        
        il.Emit(OpCodes.Ldarg_1); // Save parameter on stack
        il.Emit(OpCodes.Callvirt, realSquareFunc.GetType().GetMethod("Invoke")); // Invoke delegate
        il.Emit(OpCodes.Ret); // Return value from function call before

        var myMethod = (Func<Func<int, long>, int, long>)squareIt
            .CreateDelegate(typeof(Func<Func<int, long>, int, long>));
        var result = myMethod.Invoke(realSquareFunc, 4); // Should be 16 (4*4)
    }  
}

带参数的 C# 反射发出调用

C# Reflection Emit Call with parameter

c#

reflection

reflection.emit

func

dynamicmethod