Question

我有一个带有私有静态方法的类，带有可选参数。如何通过Reflection从另一个类调用它？有一个类似的question，但它没有解决静态方法或可选参数。

public class Foo {
    private static void Bar(string key = "") {
       // do stuff
    }
}

如何调用Foo.Bar("test")和Foo.Bar()（例如，不传递可选参数）？

Answer 1

C＃中的可选参数值是通过在调用点注入这些值来编译的。即即使您的代码是

Foo.Bar()

编译器实际上会生成类似

的调用

Foo.Bar("")

找到方法时，需要将可选参数视为常规参数。

var method = typeof(Foo).GetMethod("Bar", BindingFlags.Static | BindingFlags.NonPublic);

如果您确切知道要调用方法的值，可以执行以下操作：

method.Invoke(obj: null, parameters: new object[] { "Test" });

如果您只有一些参数并希望遵守默认值的值，则必须检查方法的ParameterInfo个对象，以查看参数是否是可选的以及这些值是什么。例如，要打印出这些参数的默认值，您可以使用以下代码：

foreach (ParameterInfo pi in method.GetParameters())
{
    if (pi.IsOptional)
    {
        Console.WriteLine(pi.Name + ": " + pi.DefaultValue);
    }
}

Answer 2

使用此课程

  public class Foo
  {
    private static void Bar(string key = "undefined key", string value = "undefined value")
    {
      Console.WriteLine(string.Format("The key is '{0}'", key));
      Console.WriteLine(string.Format("The value is '{0}'", value));
    }
  }

您可以使用以下代码使用默认值

来调用它

  MethodInfo mi = typeof(Foo).GetMethod("Bar", BindingFlags.NonPublic | BindingFlags.Static);
  ParameterInfo[] pis = mi.GetParameters();

  object[] parameters = new object[pis.Length];

  for (int i = 0; i < pis.Length; i++)
  {
    if (pis[i].IsOptional)
    {
      parameters[i] = pis[i].DefaultValue;
    }
  }

  mi.Invoke(null, parameters);

如果方法有一些非可选参数，则必须在调用方法之前将它们插入参数数组中。

E.g

private static void Bar(int number, string key = "undefined key", string value = "undefined")

需要你做

parameters[0] = "23"

在调用之前

Answer 3

我为单元测试写的东西：

    /// <summary>
    /// Attempts to execute a function and provide the result value against the provided source object even if it is private and/or static. Just make sure to provide the correct BindingFlags to correctly identify the function.
    /// </summary>
    /// <typeparam name="TReturn">The expected return type of the private method.</typeparam>
    /// <param name="type">The object's Type that contains the private method.</param>
    /// <param name="source">The object that contains the function to invoke. If looking for a static function, you can provide "null".</param>
    /// <param name="methodName">The name of the private method to run.</param>
    /// <param name="flags">Binding flags used to search for the function. Example: (BindingFlags.NonPublic | BindingFlags.Static) finds a private static method.</param>
    /// <param name="output">The invoked function's return value.</param>
    /// <param name="methodArgs">The arguments to pass into the private method.</param>
    /// <returns>Returns true if function was found and invoked. False if function was not found.</returns>
    private static bool TryInvokeMethod<TReturn>(Type type, object source, string methodName, BindingFlags flags, out TReturn output, params object[] methodArgs)
    {
        var method = type.GetMethod(methodName, flags);
        if(method != null)
        {
            output = (TReturn)method.Invoke(source, methodArgs);
            return true;
        }

        // Perform some recursion to walk the inheritance. 
        if(type.BaseType != null)
        {
            return TryInvokeMethod(type.BaseType, source, methodName, flags, out output, methodArgs);
        }

        output = default(TReturn);
        return false;
    }

然后像这样调用它以调用私有静态函数：

var success = TryInvokeMethod(typeof(Foo), null, "MyPrivateStaticFunc", BindingFlags.NonPublic | BindingFlags.Static, out result, arg1ToPass);

免责声明：我仅将其用于具有返回值的函数。尝试执行没有返回值的方法将引发异常。

如何通过反射执行带有可选参数的私有静态方法？

3 个答案: