C#在运行时自动生成方法回调

Question

我想将运行时方法绑定到类方法(如果我调用运行时方法，它必须调用我的类方法，无论是否带有参数和返回值(。

如果我不在invoke方法和Callback方法上设置参数，我的代码就会工作，但是，如果我设置了参数，我会得到错误："give error parameter count mismatch"：我该如何修复它？

    public class RunNow
{
    public void Run(string hoo)
    {
    }
    public void Callback(string ali)
    {
        Console.WriteLine("yessss");
    }
}
class Program
{
    static void Main(string[] args)
    {
        RunNow run = new CSMethodInjection.RunNow();
        var methodToCall = run.GetType().GetMethod("Callback");
        var t = GenerateType(run.GetType().Name, methodToCall);
        if (t != null)
        {
            object o = Activator.CreateInstance(t);
            MethodInfo helloWorld = t.GetMethod(methodToCall.Name);
            if (helloWorld != null)
            {
                helloWorld.Invoke(o, new object[] { "aaaaa" });//give error Parameter count mismatch.
            }
        }
        Console.ReadLine();
    }
    static Type GenerateType(string className, MethodInfo toCall)
    {
        AppDomain currentDomain = AppDomain.CurrentDomain;
        AssemblyName assemName = new AssemblyName();
        assemName.Name = "InjectionAssembly";
        AssemblyBuilder assemBuilder = currentDomain.DefineDynamicAssembly(assemName, AssemblyBuilderAccess.Run);
        ModuleBuilder moduleBuilder = assemBuilder.DefineDynamicModule("InjectionModule");
        TypeBuilder typeBuilder = moduleBuilder.DefineType(className, TypeAttributes.Public);
        MethodBuilder methodBuilder = typeBuilder.DefineMethod(toCall.Name, MethodAttributes.Public, null, null);
        List<Type> parameters = new List<Type>();
        foreach (var item in toCall.GetParameters())
        {
            parameters.Add(item.ParameterType);
            var pBuilder = methodBuilder.DefineParameter(item.Position, item.Attributes, item.Name);
        }
        if (parameters.Count > 0)
            methodBuilder.SetParameters(parameters.ToArray());
        methodBuilder.SetReturnType(toCall.ReturnType);
        ILGenerator msilG = methodBuilder.GetILGenerator();
        msilG.Emit(OpCodes.Ldarg_0);
        msilG.Emit(OpCodes.Call, toCall);
        msilG.Emit(OpCodes.Ret);
        return typeBuilder.CreateType();
    }
}

Answer 1

要修复计数错误，您可以删除或注释掉错误填充参数列表的foreach，并执行而不是

 MethodBuilder methodBuilder = typeBuilder.DefineMethod(toCall.Name, 
     MethodAttributes.Public,
     toCall.ReturnType, 
     toCall.GetParameters().Select(x => x.ParameterType).ToArray());

那么您的生成器中仍然存在其他问题，我们可以通过下面的来简化它

ILGenerator msilG = methodBuilder.GetILGenerator();
msilG.EmitWriteLine("Hello World"); // or much better see below
msilG.Emit(OpCodes.Ret);
return typeBuilder.CreateType();

或者，好多了，用替换我上面的msilG.EmitWriteLine("Hello World");

msilG.Emit(OpCodes.Ldarg_0);
msilG.Emit(OpCodes.Ldarg_1); // it's cool, isn't it?
msilG.Emit(OpCodes.Call, toCall);    

最后，您还可以调整回调；(

public void Callback(string ali)
{
    Console.WriteLine(ali); // let me see "aaaaa"
}