我的使用語句應該放在哪裏？試試抓住哪裏？

Question

我剛剛開始使用filestream，雖然我讓代碼工作，但我真的很喜歡它:)我不知道在哪裏放置使用語句，所以我可以跳過stream.Close（ ）以及如何最終使用try catch。這裏是我的代碼，不是最漂亮的東西，但它的工作原理。雙文件流用於清除文件。

編輯：對不起張貼的代碼片段臉紅這是很糟糕的：P我已經張貼了我的第二次嘗試:)

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

您不必打開文件不止一次 - 而你實際上打開它三個次。這應該沒問題; File.CreateText將截斷文件，如果它已經存在，否則創建：

// 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) 
} 

現在，你說你要使用的try/catch /終於 - 但爲什麼呢？如果你不能寫入文件，你是否確實想用這種方法「處理」異常，而不是讓它冒泡給調用者？

Answer 2

您可以跳過兩個第一FileStreams，只使用StreamWriter，它會爲你創建一個文件：

// 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

類型：System .Boolean確定數據是否爲被附加到 文件。如果文件存在並且追加爲false，則該文件被覆蓋。 如果文件存在且附加爲真，則數據將附加到 文件中。 否則，將創建一個新文件。

編輯：關於更新的問題（第二部分）

你並不需要手動刪除文件，只需指定追加在StreamWriter構造=假，它會覆蓋文件：

如果文件存在，並且append爲false，則文件被覆蓋

Answer 3

眼下，鱈魚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); 
     } 
    } 
} 

但我不知道爲什麼你打開的第一個文件。
對於第二個，我相信你試圖用這種方法創建文件，
但也有其他的方法來做到這一點。

Answer 4

首先，我不明白這麼多數據流的使用，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，我將使用LINQ :-)

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

該版本需要.NET 4.0。 File.WriteAllLines將創建該文件，寫入所有行並關閉文件。 _shipments.Select(p => string.Format("{0},{1}", shipment.Distance, shipment.Distance))將返回，爲_shipments每個元素，包含shipment.Distance + "," + shipment.Distance一個字符串中使用的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); 
     } 
}