在c#中如何操作文本文件

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// C#文本文件操作
//如何向现有文件中添加文本

using System;using System.IO;
class Test {
public static void Main()     {
// Create an instance of StreamWriter to write text to a file.        // The using statement also closes the StreamWriter.        using
(StreamWriter sw = new StreamWriter("TestFile.txt"))
{// Add some text to the file.
sw.Write("This is the ");
sw.WriteLine("header for the file.");
sw.WriteLine("-------------------");
// Arbitrary objects can also be written to the file.
sw.Write("The date is: ");
sw.WriteLine(DateTime.Now);
}
}
}

//如何创建一个新文本文件并向其中写入一个字符串。WriteAllText方法可提供类似的功能。
using System;
using System.IO;
public class TextToFile {
private const string FILE_NAME = "MyFile.txt";
public static void Main(String[] args)
{
     if (File.Exists(FILE_NAME))
     {
       Console.WriteLine("{0} already exists.", FILE_NAME);
       return;
     }
     using (StreamWriter sw = File.CreateText(FILE_NAME))
     {
        sw.WriteLine ("This is my file.");
        sw.WriteLine ("I can write ints{0} or floats {1}, and so on.", 1, 4.2);
        sw.Close();
        }
        }
}

//如何从文本文件中读取文本
using System;using System.IO;
class Test {
public static void Main()
{
    try{
      // Create an instance of StreamReader to read from a file.
      // The using statement also closes the StreamReader.
      using (StreamReader sr = new StreamReader("TestFile.txt"))
      {String line;
      // Read and display lines from the file until the end of
       // the file is reached.
           while ((line = sr.ReadLine()) != null) {
             Console.WriteLine(line);
             }
             }
             }
             catch (Exception e)
             {
             // Let the user know what went wrong.
               Console.WriteLine("The file could not be read:");
               Console.WriteLine(e.Message);
               }
               }
               }

//在检测到文件结尾时向您发出通知。通过使用 ReadAll 或 ReadAllText 方法也可以实现此功能。
               using System;using System.IO;
               public class TextFromFile {
                 private const string FILE_NAME= "MyFile.txt";
                 public static void Main(String[] args)
                 {
                    if (!File.Exists(FILE_NAME))
                    {
                       Console.WriteLine("{0} does not exist.", FILE_NAME);
                       return;
                    }
                    using (StreamReader sr = File.OpenText(FILE_NAME))
                    {
                       String input;
                       while ((input=sr.ReadLine())!=null){
                          Console.WriteLine(input);
                       }
                       Console.WriteLine ("The end of the stream has been reached.");
                    sr.Close();
                    }
                    }