Question

我正在尝试使用Reflection调用类的函数（假设对象初始化不依赖于要调用的函数），就像这样

/// <summary>
    /// Calls a static public method. 
    /// Assumes that the method returns a string
    /// </summary>
    /// <param name="assemblyName">name of the assembly containing the class in which the method lives.</param>
    /// <param name="namespaceName">namespace of the class.</param>
    /// <param name="typeName">name of the class in which the method lives.</param>
    /// <param name="methodName">name of the method itself.</param>
    /// <param name="stringParam">parameter passed to the method.</param>
    /// <returns>the string returned by the called method.</returns>
    /// 
    public static string InvokeStringMethod5(string assemblyName, string namespaceName, string typeName, string methodName, string stringParam)
    {
        //This method was created incase Method has params with default values. If has params will return error and not find function
        //This method will choice and is the preffered method for invoking 

        // Get the Type for the class
        Type calledType = Type.GetType(String.Format("{0}.{1},{2}", namespaceName, typeName, assemblyName));
        String s = null;

        // Invoke the method itself. The string returned by the method winds up in s.
        // Note that stringParam is passed via the last parameter of InvokeMember, as an array of Objects.

        if (MethodHasParams(assemblyName, namespaceName, typeName, methodName))
        {
            s = (String)calledType.InvokeMember(
                        methodName,
                        BindingFlags.InvokeMethod | BindingFlags.Public | BindingFlags.Static,
                        null,
                        null,
                        new Object[] { stringParam });
        }
        else
        {
            s = (String)calledType.InvokeMember(
            methodName,
            BindingFlags.InvokeMethod | BindingFlags.Public | BindingFlags.Static,
            null,
            null,
            null);
        }

        // Return the string that was returned by the called method.
        return s;

    }

    public static bool MethodHasParams(string assemblyName, string namespaceName, string typeName, string methodName)
    {
        bool HasParams;
        string name = String.Format("{0}.{1},{2}", namespaceName, typeName, assemblyName);
        Type calledType = Type.GetType(name);
        MethodInfo methodInfo = calledType.GetMethod(methodName);
        ParameterInfo[] parameters = methodInfo.GetParameters();

        if (parameters.Length > 0)
        {
            HasParams = true;
        }
        else
        {
            HasParams = false;
        }

        return HasParams;

    }

这是从here开始的。

还有其他/更好的方法吗？

这项活动可以是一般性的。与使用Dynamic一样，可以在.Net 4.0中调用Non-Static methods，以便返回类型可以是独立的。

我从未在实际场景中使用过dynamic关键字（仅读取一些示例）以确定我仍然不知道的使用情况

在这方面的任何帮助/方向将不胜感激谢谢

Answer 1

在dynamic上回答您的问题;不，这不适合这里。当成员名称（或操作）在编译时已知时，dynamic很有用，但不能证明存在 - 基本上是鸭子类型。例如：

dynamic foo = GetSomeRandomObject();
foo.ThisShouldExist("abc");

这类似的事情，但用法不同。所以，是的，你留下了反思。你在做什么是非常正确的。我唯一可以改变的就是获取MethodInfo，然后从那里开始工作 - 尽管如果你可以改变API来接受单个string assemblyQualifiedName，它将更加方便和灵活。但也许：

public static string InvokeStringMethod5(string assemblyName,
    string namespaceName, string typeName, string methodName, string stringParam)
{
    string assemblyQualifiedName = string.Format("{0}.{1},{2}",
        namespaceName, typeName, assemblyName);
    Type calledType = Type.GetType(assemblyQualifiedName);
    if(calledType == null) throw new InvalidOperationException(
        assemblyQualifiedName + " not found");
    MethodInfo method = calledType.GetMethod(methodName,
        BindingFlags.Public | BindingFlags.Static);
    switch (method.GetParameters().Length)
    {
        case 0:
            return (string)method.Invoke(null, null);
        case 1:
            return (string)method.Invoke(null, new object[] { stringParam });
        default:
            throw new NotSupportedException(methodName
                + " must have 0 or 1 parameter only");
    }
}

Answer 2

要回答有关如何将结果转换为泛型返回类型的问题，该方法应如下所示：

public static T InvokeMethod<T>(string assemblyName, string namespaceName, string typeName, string methodName, string stringParam)
{
    // instead of String s = null;
    T methodResult = default(T);

    // instead of s = (String)calledType.InvokeMember(...)
    methodResult = (T)calledType.InvokeMember(...);

    // return s;
    return methodResult;
}

使用类名和方法名调用类的成员

2 个答案: