/// <summary>
/// 
/// </summary>
public class testFar
{
    private string o="0";

    private string path = "";
    public string O
    {
      get { return o; }
      set { o = value; }
    }

    public string testfun()
    {
        if (path != "")
        {
            return path + "sdfsdfsd";
        }
        else
        { 
            return "没有给path值，请使用构造函数"
        }
    }

    /// <summary>
    /// 这里在继承时如何使用啊?
    /// </summary>
   public  testFar(string pp)
   {
       path = "sjflksjdlkf" + pp;
   }
}

/// <summary>
/// 这里怎么使  testFar 的构造函数的
/// </summary>
public class FromTest : testFar
{
    public FromTest()
    {
        //如何调用 testFar的构造函数
    }
}