c#读取写入文本文件

读取文本文件：

class ReadFromFile{    static void Main()    {        // The files used here were created in the code example        // in How to: Write to a Text File. You can of course substitute        // other files of your own.        // Example #1        // Read the file as one string.        string text = System.IO.File.ReadAllText(@"filename");        // Display the file contents to the console.        System.Console.WriteLine("Contents of writeText.txt = {0}", text);        // Example #2        // Read the file lines into a string array.        string[] lines = System.IO.File.ReadAllLines(@"filename");                    System.Console.WriteLine("Contents of writeLines2.txt =:");        foreach (string line in lines)        {            Console.WriteLine("\t" + line);        }        // Keep the console window open in debug mode.        Console.WriteLine("Press any key to exit.");        System.Console.ReadKey();    }} 

一次读取一行文本文件

int counter = 0;string line;// Read the file and display it line by line.System.IO.StreamReader file =    new System.IO.StreamReader(@"c:\test.txt");while((line = file.ReadLine()) != null){    System.Console.WriteLine (line);    counter++;}file.Close();System.Console.WriteLine("There were {0} lines.", counter);// Suspend the screen.System.Console.ReadLine();

写入文本文件：

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(@"filename", 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(@"filename", text);        // Example #3: Write only some strings in an array to a file.        using (System.IO.StreamWriter file = 

new System.IO.StreamWriter(@"filename"))        {            foreach (string line in lines)            {                if (line.Contains("Second") == false)                {                    file.WriteLine(line);                }            }        }        // Example #4: Append new text to an existing fileusing 

(System.IO.StreamWriter file = new System.IO.StreamWriter(@"filename", 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 */