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
*/