写入文本文件（C# 编程指南）

以下示例给出了将文本写入文件的各种方法。前两个示例使用 System.IO.File 类中的静态方法将完整的字符串数组或完整字符串写入文本文件。
示例 #3 说明如果在将文本写入文件之前必须分别处理文本的每一行，应该如何将这些文本添加到文件中。示例 1-3 均覆盖文件中的所有现有
内容。示例 #4 说明如何将文本追加到现有文件的末尾。

class WriteTextFile{    static void Main()    {        // These examples assume a "C:/Users/Public/TestFolder" folder on your machine.        // You can modify the path if necessary.        // Example #1: Write an array of strings to a file.        // Create a string array that consists of three lines.        string[] lines = {"First line", "Second line", "Third line"};        System.IO.File.WriteAllLines(@"C:/Users/Public/TestFolder/WriteLines.txt", lines);        // Example #2: Write one string to a text file.        string text = "A class is the most powerful data type in C#. Like structures, " +                       "a class defines the data and behavior of the data type. ";        System.IO.File.WriteAllText(@"C:/Users/Public/TestFolder/WriteText.txt", text);        // Example #3: Write only some strings in an array to a file.        using (System.IO.StreamWriter file = new System.IO.StreamWriter(@"C:/Users/Public/TestFolder/WriteLines2.txt"))        {            foreach (string line in lines)            {                if (line.Contains("Second") == false)                {                    file.WriteLine(line);                }            }        }        // Example #4: Append new text to an existing file        using (System.IO.StreamWriter file = new System.IO.StreamWriter(@"C:/Users/Public/TestFolder/WriteLines2.txt", true))        {            file.WriteLine("Fourth line");        }      }}/* Output (to WriteLines.txt):    First line    Second line    Third line Output (to WriteText.txt):    A class is the most powerful data type in C#. Like structures, a class defines the data and behavior of the data type. Output to WriteLines2.txt after Example #3:    First line    Third line Output to WriteLines2.txt after Example #4:    First line    Third line    Fourth line */