扩展基类方法

Question

我是C#的新手,我正在尝试理解基本概念.预先感谢您的帮助.我在下面有一些示例类(在此窗口中键入以便可能存在一些错误)并且有两个问题:

1. 是否可以调用以相同名称执行基类方法中的代码的派生类方法,然后在派生类方法中执行代码？每个派生类都需要为RunCheck执行基类代码,然后执行特定于其类的专用代码.我可以在基类中命名RunCheck(),然后在调用派生类的RunCheck()时调用它,但是我必须记得在派生类的RunCheck()上调用它.

2. 在Program.cs中,我想输出一个空值的所有字段,如果它在一个不在我传入的派生类中的字段上.我会传入什么？

这是我的代码:

  class baseCheck
  {
      public DateTime StartTime { get; set; }
      public DateTime LastRun { get; set; }
      public int Runs { get; set; }
      //Others

      public void RunCheck()
      {
         if (Started != null)
           started = DateTime.Now;

         LastRun = DateTime.Now;

         Runs++;
      }
    }

    class FileCheck : baseCheck
    {
       public string FileName { get; set; }

       public void RunCheck()
       {
           //I want all the code in the base class to run plus
           //any code I put here when calling this class method

        }
    }
    class DirectoryCheck : baseCheck
    {
       public string DirectoryName { get; set; }

       public void RunCheck()
       {
           //I want all the code in the base class to run plus
           //any code I put here when calling this class method

        }
    }

        //Program.cs
        static void Main()
        {
           //Create derived class - either DirectoryCheck or FileCheck
           //depending on what the user chooses.

            if (Console.ReadLine()=="F")
            {
                FileCheck c = new FileCheck();  
            }
            else
            {
                DirectoryCheck c = new DirectoryCheck();
            }

            PrintOutput(c);

        }
        private void PrintOut(What do I put here?)
        {
           Console.WriteLine("Started: {0}",f.StartTime)
           Console.WriteLine("Directory: {0}", f.DirectoryName)
           Console.WriteLine("File: {0}", f.FileName}
        }

Answer 1

只需打电话给base.RunCheck()你的DirectoryCheck班级:

public class DirectoryCheck : baseCheck
{
    public string DirectoryName { get; set; }

    public void RunCheck()
    {
        //I want all the code in the base class to run plus
        //any code I put here when calling this class method
        base.RunCheck();
        Console.WriteLine("From DirectoryCheck");
    }
}

另外,对于当前的实现,您隐藏了基类RunCheck()方法 - 您应该实际覆盖它 - 这会将基类中的方法签名更改为

    public virtual void RunCheck()

并在派生类中

    public override void RunCheck()

我怀疑你真正想要的是非虚拟接口模式(NVI) - 在你的基类中公开一个受保护的虚方法,子类可以覆盖,但在基类上有一个实际调用该方法的公共方法内部 - 这种方法允许您扩展您在该呼叫之前和之后所做的事情.

在您的示例中,这将如下所示:

class BaseCheck
{
    private DateTime Started { get; set; }
    public DateTime StartTime { get; set; }
    public DateTime LastRun { get; set; }
    public int Runs { get; set; }
    //Others

    public void RunCheck()
    {
        if (Started != null)
            Started = DateTime.Now;

        LastRun = DateTime.Now;
        Runs++;
        CoreRun();
    }

    protected virtual void CoreRun()
    {

    }
}


public class DirectoryCheck : BaseCheck
{
    public string DirectoryName { get; set; }

    protected override void CoreRun()
    {
        //I want all the code in the base class to run plus
        //any code I put here when calling this class method
        Console.WriteLine("From DirectoryCheck");
    }
}