如何：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。
示例
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 the line doesn't contain the word 'Second', write the line to the file.
if (!line.Contains("Second"))
{
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
*/
编译代码
将代码复制到控制台应用程序中。
将 "c:\testdir" 替换为您计算机上的实际文件夹名称，或者创建一个此名称的文件夹。
可靠编程
以下情况可能会导致异常：
文件已存在并且为只读。
路径名可能太长。
磁盘可能已满。