我的使用语句应该放在哪里？试试抓住哪里？

Question

我刚刚开始使用filestream，虽然我让代码工作，但我真的很喜欢它:)我不知道在哪里放置使用语句，所以我可以跳过stream.Close（ ）以及如何最终使用try catch。这里是我的代码，不是最漂亮的东西，但它的工作原理。双文件流用于清除文件。

编辑：对不起张贴的代码片段脸红这是很糟糕的：P我已经张贴了我的第二次尝试:)

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

您不必打开文件不止一次 - 而你实际上打开它三个次。这应该没问题; File.CreateText将截断文件，如果它已经存在，否则创建：

// 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，你说你要使用的try/catch /终于 - 但为什么呢？如果你不能写入文件，你是否确实想用这种方法“处理”异常，而不是让它冒泡给调用者？

Answer 2

您可以跳过两个第一FileStreams，只使用StreamWriter，它会为你创建一个文件：

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

MSDN:

public StreamWriter(
    string path, 
    bool append, 
    Encoding encoding 
) 

追加

类型：System .Boolean确定数据是否为被附加到 文件。如果文件存在并且追加为false，则该文件被覆盖。 如果文件存在且附加为真，则数据将附加到 文件中。 否则，将创建一个新文件。

编辑：关于更新的问题（第二部分）

你并不需要手动删除文件，只需指定追加在StreamWriter构造=假，它会覆盖文件：

如果文件存在，并且append为false，则文件被覆盖

Answer 3

眼下，鳕鱼è您已是相同的：

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

    using(FileStream f = File.Open("Shipping2.txt", FileMode.Create)) {} 

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

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

但我不知道为什么你打开的第一个文件。
对于第二个，我相信你试图用这种方法创建文件，
但也有其他的方法来做到这一点。

Answer 4

首先，我不明白这么多数据流的使用，但你可以使用使用了一些地方：

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

    } 

    using(var f = File.Open("Shipping2.txt", FileMode.Create)) 
    { 

    } 

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

     }; 
    } 
} 

Answer 5

只要是不同的，我将使用LINQ :-)

File.WriteAllLines(
    "Shipping2.txt", 
    _shipments.Select(
     p => string.Format(
      "{0},{1}", 
      shipment.Distance, 
      shipment.Distance) 
    ), 
    Encoding.ASCII); 

该版本需要.NET 4.0。 File.WriteAllLines将创建该文件，写入所有行并关闭文件。 _shipments.Select(p => string.Format("{0},{1}", shipment.Distance, shipment.Distance))将返回，为_shipments每个元素，包含shipment.Distance + "," + shipment.Distance一个字符串中使用的StreamWriter追加=假文件（使用string.Format格式） `

Answer 6

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