IL 生成用户定义函数的代理<TInput, TReturn>

Question

我正在尝试动态生成程序集来调用用户创建的函数。

private MethodBuilder DefineGetMethod<TInput, TReturn>(
     TypeBuilder tb, MethodDescriptor methodInfo, Func<TInput, TReturn> dynamicMethod)
{
    //Define the function
    var dynamicMethodBuilder = tb.DefineMethod(methodInfo.MethodName,
              MethodAttributes.Public,
              methodInfo.ReturnType, methodInfo.InputParameters.Select(x => x.Type).ToArray());

    //Define the labels for the method inputs
    for(var i = 0; i < methodInfo.InputParameters.Length; i++ )
    {
        // Position 0 is the return value, 1 is the 1st param, 2 is 2nd, etc.
        var position = 1 + i;
        var inputParam = methodInfo.InputParameters[i];
        dynamicMethodBuilder.DefineParameter(position, ParameterAttributes.None, inputParam.Name);
    }

    var ilGenerator = dynamicMethodBuilder.GetILGenerator();

    //Loads arg1
    ilGenerator.Emit(OpCodes.Ldarg_1);

    //Not sure how to pass the arg1 to the method body to return
    var ilMethodBody = dynamicMethod.Method.GetMethodBody().GetILAsByteArray();

    //Generates return
    ilGenerator.Emit(OpCodes.Ret);

}

编辑
我反编译了现有代码，以与反编译现有代码类似的方式调用方法，但我仍然无法让它工作

// Argument 1 of dynamic method is argument array.
myMethodIL.Emit(OpCodes.Ldarg_1);
myMethodIL.Emit(OpCodes.Callvirt, method.Method);
myMethodIL.Emit(OpCodes.Stloc_0);
myMethodIL.Emit(OpCodes.Ldloc_0);
myMethodIL.Emit(OpCodes.Ret);

如何将加载的参数传递给 ilMethodBody 和 return？

Answer 1

编辑 - 约翰尼 5

原来只需要跳转到已有的方法信息即可：

myMethodIL.Emit(OpCodes.Jmp, method.Method);
myMethodIL.Emit(OpCodes.Ret);

首先，您必须确保 TReturn 等于 methodInfo.ReturnType 并且 TInput 等于 methodInfo.InputParameters 中的第一个。

如果dynamicMethod是一个静态方法委托，它会很容易像：

private MethodBuilder DefineGetMethod<TInput, TReturn>(TypeBuilder tb, MethodDescriptor methodInfo, Func<TInput, TReturn> dynamicMethod)
{
    var dynamicMethodBuilder = tb.DefineMethod(methodInfo.MethodName,
                MethodAttributes.Public | MethodAttributes.HideBySig,
                methodInfo.ReturnType, methodInfo.InputParameters.Select(x => x.Type).ToArray());

    var ilGenerator = dynamicMethodBuilder.GetILGenerator();

    ilGenerator.Emit(OpCodes.Ldarg_1);
    ilGenerator.Emit(OpCodes.Call, dynamicMethod.Method);
    ilGenerator.Emit(OpCodes.Ret);

    return dynamicMethodBuilder;
}

但是如果 dynamicMethod 可能是一个实例方法（lambda 是一个实例方法），那就很难了。调用实例方法需要先将实例压入栈中，但Emit只允许压入常量值，如int、string。

我只能想到一个方法，声明一个字段存储dynamicMethod，通过reflect在构建类型后设置字段值：

private Type DefineGetMethod<TInput, TReturn>(TypeBuilder tb, MethodDescriptor methodInfo, Func<TInput, TReturn> dynamicMethod)
{
    var fieldBuilder = tb.DefineField("_func", dynamicMethod.GetType(), FieldAttributes.Private | FieldAttributes.Static);

    var dynamicMethodBuilder = tb.DefineMethod(methodInfo.MethodName,
                MethodAttributes.Public | MethodAttributes.HideBySig,
                methodInfo.ReturnType, methodInfo.InputParameters.Select(x => x.Type).ToArray());

    var ilGenerator = dynamicMethodBuilder.GetILGenerator();

    // load static field _func onto stack
    ilGenerator.Emit(OpCodes.Ldsfld, fieldBuilder);
    // load arg1 onto stack
    ilGenerator.Emit(OpCodes.Ldarg_1);
    // call _func.Invoke(..)
    ilGenerator.Emit(OpCodes.Callvirt, dynamicMethod.GetType().GetMethod("Invoke"));
    ilGenerator.Emit(OpCodes.Ret);

    var type = tb.CreateType();
    var field = type.GetField("_func", BindingFlags.NonPublic | BindingFlags.Static);
    // store dynamicMethod into static field _func
    field.SetValue(null, dynamicMethod);
    return type;
}

编辑

测试代码：

class Program
{
    static void Main(string[] args)
    {
        OnlyStaticFunc();
        StaticField();
    }

    static void OnlyStaticFunc()
    {
        Func<string, int> func = int.Parse;

        var assemblyName = new AssemblyName("StaticFuncTest");
        var assemblyBuilder = AssemblyBuilder.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Run);
        var moduleBuilder = assemblyBuilder.DefineDynamicModule(assemblyName.Name);
        var typeBuilder = moduleBuilder.DefineType("Abc", TypeAttributes.Public);
        var methodBuilder = typeBuilder.DefineMethod("Execute", MethodAttributes.Public | MethodAttributes.HideBySig, typeof(int), new[] { typeof(string) });

        var il = methodBuilder.GetILGenerator();
        il.Emit(OpCodes.Ldarg_1);
        il.Emit(OpCodes.Call, func.Method);
        il.Emit(OpCodes.Ret);

        var type = typeBuilder.CreateType();
        var abc = Activator.CreateInstance(type);
        var value = ((dynamic)abc).Execute("123");
        Console.WriteLine($"only static func: {value}");
    }

    static void StaticField()
    {
        Func<string, int> func = s => int.Parse(s);

        var assemblyName = new AssemblyName("StaticFieldTest");
        var assemblyBuilder = AssemblyBuilder.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Run);
        var moduleBuilder = assemblyBuilder.DefineDynamicModule(assemblyName.Name);
        var typeBuilder = moduleBuilder.DefineType("Abc", TypeAttributes.Public);
        var fieldBuilder = typeBuilder.DefineField("_func", func.GetType(), FieldAttributes.Private | FieldAttributes.Static);
        var methodBuilder = typeBuilder.DefineMethod("Execute", MethodAttributes.Public | MethodAttributes.HideBySig, typeof(int), new[] { typeof(string) });

        var il = methodBuilder.GetILGenerator();
        il.Emit(OpCodes.Ldsfld, fieldBuilder);
        il.Emit(OpCodes.Ldarg_1);
        il.Emit(OpCodes.Callvirt, func.GetType().GetMethod("Invoke"));
        il.Emit(OpCodes.Ret);

        var type = typeBuilder.CreateType();
        var field = type.GetField("_func", BindingFlags.NonPublic | BindingFlags.Static);
        field.SetValue(null, func);
        var abc = Activator.CreateInstance(type);
        var value = ((dynamic)abc).Execute("456");
        Console.WriteLine($"static field: {value}");
    }
}

IL 生成用户定义函数的代理<TInput, TReturn>

IL Generate Proxy to User Define Func<TInput, TReturn>

c#

reflection

code-generation

.net-core