c# - 我的 using 语句应该放在哪里？在哪里放置try catch？

Question

我刚刚开始使用文件流，虽然我使代码可以工作，但我真的很想让它变得漂亮 :) 我不知道在哪里放置 using 语句以便我可以跳过流。关闭()，以及如何使用try catch finally。这是我的代码，不是最漂亮的代码，但它可以工作。双文件流用于清除文件。

编辑:很抱歉发布了非常糟糕的代码片段脸红 :P 我已经发布了我的第二次尝试:)

internal static void SaveFileAsTxt()
{
    FileStream streamer = new FileStream("Shipping2.txt", FileMode.Append, FileAccess.Write, FileShare.Write);
    streamer.Close();

    FileStream f = File.Open("Shipping2.txt", FileMode.Create);  
    f.Close();

    StreamWriter writer = new StreamWriter("Shipping2.txt", true, Encoding.ASCII);

    foreach (var shipment in _shipments)
    {
        string write = (shipment.Distance + ","+ shipment.Distance).ToString();
        writer.WriteLine(write);

    };

        writer.Close();
}


//--------new code--------


internal static void SaveFileAsTxt()
{
    if (File.Exists("Shipping2.txt"))
    {
        File.Delete("Shipping2.txt");
    }

    using (StreamWriter writer = new StreamWriter("Shipping2.txt", true, Encoding.ASCII))
    { 
        foreach (var shipment in _shipments)
        {
            string write = (shipment.Duration + ","+ shipment.Distance).ToString();
                        writer.WriteLine(write);
        }
    } 
}

Answer 1

您不需要多次打开该文件 - 实际上您现在打开它 三次 次。这应该没问题； File.CreateText如果文件已经存在，将截断该文件，否则创建它:

// Are you *sure* you want to use ASCII? UTF-8 might be a better bet...
using (TextWriter writer = File.CreateText("Shipping2.txt", Encoding.ASCII))
{
    foreach (var shipment in _shipments)
    {
        // Removed redundant ToString call, and elided local variable.
        // Consider using a format string instead:
        // writer.WriteLine("{0},{1}", shipment.Distance, shipment.Distance);
        writer.WriteLine(shipment.Distance + "," + shipment.Distance);
    }
    // Removed empty statement (trailing semi-colon)
}

现在，你说你想使用 try/catch/finally - 但为什么呢？如果写入文件失败，您是否肯定希望在此方法中“处理”异常，而不是让它冒泡给调用者？