C#如何在构造函数中增加变量-Windows服务[关闭]

Question

我有一个 Windows 服务，我想在调用构造函数时更改 URL。我通过将变量连接到构造函数中来形成 URL，并且变量正在递增（如下面的代码所示）。

但是，URL 没有改变，我仍然从 URL 下载相同的 XML 文件。

我试过这个：

private string Url;
    private string Name = @"D:\test\userko.xml";
    private System.Timers.Timer timer;

    private Downloader xd;
    private static int i;



    public Service1()
    {
        InitializeComponent();
        while (i < 5000)
        {
            Url = "http://tis-toolbox.appspot.com/api/user/id/" + i + ".xml";
            i++;
            if (i == 4999)
                i = 0;
            break;
        }

        xd = new Downloader(Url, Name);
        timer = new System.Timers.Timer();
        timer.Enabled = true;
        timer.Interval = 1000;
        timer.Elapsed += new System.Timers.ElapsedEventHandler(timer_Elapsed);
    }

    protected override void OnStart(string[] args)
    {
        EventLog.WriteEntry("PCTrss reader Service Started.");
        tryDownload();
    }

    protected override void OnStop()
    {
        EventLog.WriteEntry("PCTrss reader Service was shutdown.");
    }

    private void timer_Elapsed(object sender, EventArgs e)
    {
        tryDownload();
    }

    private void tryDownload()
    {
        try
        {
            timer.Stop();
            xd.DownloadXML();
            EventLog.WriteEntry("PCTrss reader downloaded news at " + xd.LastUpdate + ". XML is in " + Name);
        }
        catch (Exception ex)
        {
            EventLog.WriteEntry("PCTrss reader Service cannot download feeds " + ex.ToString());
        }
        finally
        {
            timer.Start();
        }
    }
}

这里是下载器类。它从 URL 读取并保存一个 XML 文件。

class Downloader
{
    public DateTime LastUpdate;
    public string Url { get; set; }
    public string Name { get; set; }

    public Downloader(string url, string name) 
    {
        this.Url = url;
        this.Name = name;
    }

    public void DownloadXML()
    {
        if (!Directory.Exists(@"D:\test"))
            Directory.CreateDirectory(@"D:\test");

        LastUpdate = DateTime.Now;



        WebClient client = new WebClient();
        client.Encoding = Encoding.UTF8;
        using( Stream stream = client.OpenRead(Url) )
        using( StreamReader sr = new StreamReader(stream) )
        using( FileStream fs = new FileStream(Name, FileMode.Create, FileAccess.Write))
        using( StreamWriter sw = new StreamWriter(fs) )
        {
            string s = sr.ReadToEnd();
            sw.BaseStream.Seek(0, SeekOrigin.End);
            sw.Write(s);
        }
    }
}

Answer 1

有几个问题：

首先，正如 berXpert 所说，while 循环中的正确子句应该是 i < 5000。其次，如果要下载5000次，整个代码应该在while循环中

while (i < 5000)    
{
    Url = "http://tis-toolbox.appspot.com/api/user/id/" + i + ".xml";
    i++;
    xd = new Downloader(Url, Name);
    timer = new System.Timers.Timer();
    timer.Enabled = true;
    timer.Interval = 1000;
    timer.Elapsed += new System.Timers.ElapsedEventHandler(timer_Elapsed);
}

另外，while 循环中不需要 break，它不会执行超过 5000 次（假设 i 开始为 0）

Answer 2

一定要把while子句改成

i < 5000

并将i 作为共享静态属性

private static int;