C# 如何从 DynamicMethod 获取 RuntimeMethodHandle？

Question

我想用 .Net Framework 4 中的动态方法替换方法，然后我在 Dynamically replace the contents of a C# method? 中找到了一个非常有用的答案，但我无法直接从 DynamicMethod 获取 MethodHandle：

we cannot return a MethodHandle because we cannot track it via GC so this method is off limits

在本文中CLR Injection: Runtime Method Replacer、

private static IntPtr GetDynamicMethodRuntimeHandle(MethodBase method)
{
    if (method is DynamicMethod)
    {
        FieldInfo fieldInfo = typeof(DynamicMethod).GetField("m_method", 
                              BindingFlags.NonPublic|BindingFlags.Instance);
        return ((RuntimeMethodHandle)fieldInfo.GetValue(method)).Value;
    }
    return method.MethodHandle.Value;
}

找不到m_method。

然后注意到了m_methodHandle，但是不知道什么时候会初始化

internal unsafe RuntimeMethodHandle GetMethodDescriptor() {
    if (m_methodHandle == null) {
        lock (this) {
            if (m_methodHandle == null) {
                if (m_DynamicILInfo != null)
                    m_DynamicILInfo.GetCallableMethod(m_module, this);
                else {
                    if (m_ilGenerator == null || m_ilGenerator.ILOffset == 0)
                        throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_BadEmptyMethodBody", Name));

                    m_ilGenerator.GetCallableMethod(m_module, this);
                }
            }
        }
    }
    return new RuntimeMethodHandle(m_methodHandle);
}

根据另一个问题Resolving the tokens found in the IL from a dynamic method，DynamicResolver 有一个ResolveToken 方法return methodHandle 地址。所以我在答案中使用了一些代码：

var resolver = typeof(DynamicMethod)
    .GetField("m_resolver", BindingFlags.Instance | BindingFlags.NonPublic)
    .GetValue(dynamicMethod);
if (resolver == null) 
    throw new ArgumentException("The dynamic method's IL has not been finalized.");

但是... DynamicResolver 只会在 DynamicILGenerator.GetCallableMethod 方法中初始化，该方法将在 DynamicMethod.GetMethodDescriptor 方法中调用，所以当我得到时 resolver 必须为空它。

这是我的动态方法：

private static MethodInfo build(MethodInfo originMethod)
{
    var parameters = originMethod.GetParameters();
    var parameterTypes = parameters.Length == 0 ? 
        null :
        parameters
            .Select(param => param.ParameterType)
            .ToArray();

    DynamicMethod method = new DynamicMethod(
        originMethod.Name,
        originMethod.ReturnType,
        parameterTypes,
        originMethod.Module);

    ILGenerator il = method.GetILGenerator();
    il.Emit(OpCodes.Ldstr, "Injected");
    var console_writeline = typeof(Console).GetMethod("WriteLine", new Type[] { typeof(string) });
    il.Emit(OpCodes.Call, console_writeline);
    il.Emit(OpCodes.Ret);

    return method;
}

我学的JIT很少，不是很懂。

有人可以帮忙吗？

--------------------------------已编辑------------ --------------

@Latency 的回答很好：

RuntimeMethodHandle GetMethodRuntimeHandle(MethodBase method)
{
    if (!(method is DynamicMethod))
        return method.MethodHandle;

    RuntimeMethodHandle handle;
    if (Environment.Version.Major == 4)
    {
        var getMethodDescriptorInfo = typeof(DynamicMethod).GetMethod("GetMethodDescriptor", BindingFlags.NonPublic | BindingFlags.Instance);
        handle = (RuntimeMethodHandle)getMethodDescriptorInfo.Invoke(method, null);
    }
    else
    {
        var fieldInfo = typeof(DynamicMethod).GetField("m_method", BindingFlags.NonPublic | BindingFlags.Instance);
        handle = (RuntimeMethodHandle)fieldInfo.GetValue(method);
    }
    return handle;
}

过了这么久我不记得获取 RuntimeMethodHandle 并拒绝动态方法之后的下一步是什么，但我希望这可以帮助其他人。

Answer 1

哈哈@lock(this)

.NET Framework 在 v3.5 之后更改了内存规格

您需要输入条件以针对框架版本进行测试。

通常，您希望通过执行以下操作来重载该方法：

private static RuntimeMethodHandle GetDynamicMethodRuntimeHandle(DynamicMethod method) => method.MethodHandle;

但是，动态方法不支持此操作。

获取基本定义似乎有效。

GetDynamicMethodRuntimeHandle(DynamicMethod method) => GetDynamicMethodRuntimeHandle(method.GetBaseDefinition());

private static RuntimeMethodHandle GetDynamicMethodRuntimeHandle(MethodBase method) {
  RuntimeMethodHandle handle;    
  if (Environment.Version.Major == 4) {
    var getMethodDescriptorInfo = typeof(DynamicMethod).GetMethod("GetMethodDescriptor", BindingFlags.NonPublic | BindingFlags.Instance);
    handle = (RuntimeMethodHandle) getMethodDescriptorInfo.Invoke(method, null);
  } else {
    var fieldInfo = typeof(DynamicMethod).GetField("m_method", BindingFlags.NonPublic | BindingFlags.Instance);
    handle = (RuntimeMethodHandle) fieldInfo.GetValue(method);
  }    
  return handle;
}

可以简化为：

private static IntPtr GetDynamicMethodRuntimeHandle(MethodBase method) {
  if (!(method is DynamicMethod))
    return method.MethodHandle.Value;
  var fieldInfo = typeof(DynamicMethod).GetField("m_method", BindingFlags.NonPublic | BindingFlags.Instance);
  return fieldInfo != null ? ((RuntimeMethodHandle) fieldInfo.GetValue(method)).Value : method.MethodHandle.Value;
}

C# 如何从 DynamicMethod 获取 RuntimeMethodHandle？

C# how to get RuntimeMethodHandle from DynamicMethod?

c#

dynamicmethod