从methodinfo获得委托

Question

我有一个下拉列表，它通过检查类的方法并包括那些匹配特定签名的方法来填充。问题在于从列表中获取所选项并让委托在类中调用该方法。第一种方法起作用，但我找不出第二种方法的一部分。

例如,

public delegate void MyDelegate(MyState state);

public static MyDelegate GetMyDelegateFromString(string methodName)
{
    switch (methodName)
    {
        case "CallMethodOne":
            return MyFunctionsClass.CallMethodOne;
        case "CallMethodTwo":
            return MyFunctionsClass.CallMethodTwo;
        default:
            return MyFunctionsClass.CallMethodOne;
    }
}

public static MyDelegate GetMyDelegateFromStringReflection(string methodName)
{
    MyDelegate function = MyFunctionsClass.CallMethodOne;

    Type inf = typeof(MyFunctionsClass);
    foreach (var method in inf.GetMethods())
    {
        if (method.Name == methodName)
        {
            //function = method;
            //how do I get the function to call?
        }
    }

    return function;
}

如何使第二个方法的注释部分工作？如何将MethodInfo转换到委托中？

谢谢!

编辑:这是工作解决方案.

public static MyDelegate GetMyDelegateFromStringReflection(string methodName)
{
    MyDelegate function = MyFunctionsClass.CallMethodOne;

    Type inf = typeof(MyFunctionsClass);
    foreach (var method in inf.GetMethods())
    {
        if (method.Name == methodName)
        {
            function = (MyDelegate)Delegate.CreateDelegate(typeof(MyDelegate), method);
        }
    }

    return function;
}

Answer 1

您需要调用某种形式的Delegate.CreateDelegate()，这取决于所讨论的方法是静态方法还是实例方法。

Answer 2

public static Delegate CreateDelegate(this MethodInfo methodInfo, object target) {
    Func<Type[], Type> getType;
    var isAction = methodInfo.ReturnType.Equals((typeof(void)));
    var types = methodInfo.GetParameters().Select(p => p.ParameterType);

    if (isAction) {
        getType = Expression.GetActionType;
    }
    else {
        getType = Expression.GetFuncType;
        types = types.Concat(new[] { methodInfo.ReturnType });
    }

    if (methodInfo.IsStatic) {
        return Delegate.CreateDelegate(getType(types.ToArray()), methodInfo);
    }

    return Delegate.CreateDelegate(getType(types.ToArray()), target, methodInfo.Name);
}

Answer 3

下面是使用Expression.GetDelegateType()的Sagi解决方案的一个更简单的版本，而不是手动检测是否需要Action或Func：

public static Delegate CreateDelegate(this MethodInfo methodInfo, object target)
{
    var parmTypes = methodInfo.GetParameters().Select(parm => parm.ParameterType);
    var parmAndReturnTypes = parmTypes.Append(methodInfo.ReturnType).ToArray();
    var delegateType = Expression.GetDelegateType(parmAndReturnTypes);

    if (methodInfo.IsStatic)
        return methodInfo.CreateDelegate(delegateType);
    return methodInfo.CreateDelegate(delegateType, target);
}