調用成員

Question

我試圖調用使用Reflection一類的功能（假設對象初始化作爲功能不依賴於被調用）這樣

/// <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; 

    } 

這是取自here。

有沒有其他的/更好的方法來做到這一點？

這個活動可以是通用的嗎？與使用Dynamic類似，可以在.Net 4.0中調用Non-Static methods，以便返回類型可以獨立。

我從來沒有在實際場景中使用dynamic關鍵字（只讀一些例子）來actul使用還是未知數我

在這方面的任何幫助/方向，將不勝感激 感謝

Answer 1

回答您查詢在dynamic;不，這在這裏不太合適。 dynamic在成員名稱（或操作）在編譯時已知但不可證明存在的情況下非常有用 - 基本上，是鴨子鍵入。例如：

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

這樣做的事情相似，但用法不同。所以是的，你留下了反思。你在做什麼是非常正確的。我唯一可能改變的將是獲得MethodInfo，並從那裏開始工作 - 但如果您可以將API更改爲接受單個string assemblyQualifiedName，那將更加方便和靈活。但也許：

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

爲了回答關於如何將結果轉換到一個通用的返回類型的問題，該方法看起來是這樣的：

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; 
}