一:都用于典型的操作,如复制、移动、重命名、创建、打开、删除和追加到文件
二:默认情况下,将向所有用户授予对新文件的完全读/写访问权限。
两者的区别:
File类是静态类,由于所有的File方法都是静态的,所以如果只想执行一个操作,那么使用File方法的效率比使用相应的FileInfo 实例方法可能更高。所有的File方法都要求当前所操作的文件的路径。File 类的静态方法对所有方法都执行安全检查。如果打算多次重用某个对象,可考虑改用FileInfo的相应实例方法,因为并不总是需要安全检查。
(不老神仙个人认为:
file,directory可以控制多个文件所以进行每次安全检查,而FileInfo,DirectoryInfo只能控制一个文件信息只进行一次安全处理。
静态方法每次对文件进行操作过程是:静态方法存在于栈头,它是由类调用,然后寻找需要操作的文件。寻找需要操作文件的过程是个IO过程,耗时比较长。但它不必要到堆区去遍历实例化新对象。
普通方法是由当时的对象调用,需要创建对象,new一个,(静态方法不需要此过程)但如果操作次数多的话,普通方法就不需要再次去执行不必要而且耗时的IO操作,就能整体提速!
所以执行方法的次数也就能决定了使用哪个类的最佳选择。
参考《ASP.NET与VB.NET从入门到精通》(电子工业出版社 A.Rusell Jones 著 高春蓉 谷宇 阎隽等译))
下面的示例演示了File类的一些主要成员。
using System.IO;
class Test
{
public static void Main()
{
string path = @"c: empMyTest.txt";
if (!File.Exists(path))
{
// Create a file to write to.
using (StreamWriter sw = File.CreateText(path))
{
sw.WriteLine("Hello");
sw.WriteLine("And");
sw.WriteLine("Welcome");
}
}
// Open the file to read from.
using (StreamReader sr = File.OpenText(path))
{
string s = "";
while ((s = sr.ReadLine()) != null)
{
Console.WriteLine(s);
}
}
try
{
string path2 = path + "temp";
// Ensure that the target does not exist.
File.Delete(path2);
// Copy the file.
File.Copy(path, path2);
Console.WriteLine("{0} was copied to {1}.", path, path2);
// Delete the newly created file.
File.Delete(path2);
Console.WriteLine("{0} was successfully deleted.", path2);
}
catch (Exception e)
{
Console.WriteLine("The process failed: {0}", e.ToString());
}
}
}
File.Create 方法 (String)
参数path:要创建的文件的路径及名称。
返回值:一个 FileStream,它提供对 path 中指定的文件的读/写访问。
下面的示例在指定路径中创建一个文件,将一些信息写入该文件,再从文件中读取。
using System.IO;
using System.Text;
class Test
{
public static void Main()
{
string path = @"c: empMyTest.txt";
try
{
// Delete the file if it exists.
if (File.Exists(path))
{
File.Delete(path);
}
// Create the file.
using (FileStream fs = File.Create(path))
{
Byte[] info = new UTF8Encoding(true).GetBytes("This is some text in the file.");
// Add some information to the file.
fs.Write(info, 0, info.Length);
}
// Open the stream and read it back.
using (StreamReader sr = File.OpenText(path))
{
string s = "";
while ((s = sr.ReadLine()) != null)
{
Console.WriteLine(s);
}
}
}
catch (Exception Ex)
{
Console.WriteLine(Ex.ToString());
}
}
}
File.OpenText 方法:打开现有 UTF-8 编码文本文件以进行读取。
参数path:要打开以进行读取的文件。
返回值:指定路径上的 StreamReader。
File.CreateText 方法:创建或打开一个文件用于写入 UTF-8 编码的文本。
参数path:要打开以进行写入的文件。
返回值:一个 StreamWriter,它使用 UTF-8 编码写入指定的文件。
下面的示例创建一个文件,用于写入和读取文本。
using System.IO;
class Test
{
public static void Main()
{
string path = @"c: empMyTest.txt";
if (!File.Exists(path))
{
// Create a file to write to.
using (StreamWriter sw = File.CreateText(path))
{
sw.WriteLine("Hello");
sw.WriteLine("And");
sw.WriteLine("Welcome");
}
}
// Open the file to read from.
using (StreamReader sr = File.OpenText(path))
{
string s = "";
while ((s = sr.ReadLine()) != null)
{
Console.WriteLine(s);
}
}
}
}
下面的示例演示了 FileInfo 类的一些主要成员。
using System.IO;
class Test
{
public static void Main()
{
string path = Path.GetTempFileName();
FileInfo fi1 = new FileInfo(path);
if (!fi1.Exists)
{
//Create a file to write to.
using (StreamWriter sw = fi1.CreateText())
{
sw.WriteLine("Hello");
sw.WriteLine("And");
sw.WriteLine("Welcome");
}
}
//Open the file to read from.
using (StreamReader sr = fi1.OpenText())
{
string s = "";
while ((s = sr.ReadLine()) != null)
{
Console.WriteLine(s);
}
}
try
{
string path2 = Path.GetTempFileName();
FileInfo fi2 = new FileInfo(path2);
//Ensure that the target does not exist.
fi2.Delete();
//Copy the file.
fi1.CopyTo(path2);
Console.WriteLine("{0} was copied to {1}.", path, path2);
//Delete the newly created file.
fi2.Delete();
Console.WriteLine("{0} was successfully deleted.", path2);
}
catch (Exception e)
{
Console.WriteLine("The process failed: {0}", e.ToString());
}
}
}
using System.IO;
public class DeleteTest
{
public static void Main()
{
// Create a reference to a file.
FileInfo fi = new FileInfo("temp.txt");
// Actually create the file.
FileStream fs = fi.Create();
// Modify the file as required, and then close the file.
fs.Close();
// Delete the file.
fi.Delete();
}
}
using System.IO;
using System.Text;
class Test
{
public static void Main()
{
string path = @"c: empMyTest.txt";
FileInfo fi = new FileInfo(path);
// Delete the file if it exists.
if (fi.Exists)
{
fi.Delete();
}
//Create the file.
using (FileStream fs = fi.Create())
{
Byte[] info =
new UTF8Encoding(true).GetBytes("This is some text in the file.");
//Add some information to the file.
fs.Write(info, 0, info.Length);
}
//Open the stream and read it back.
using (StreamReader sr = fi.OpenText())
{
string s = "";
while ((s = sr.ReadLine()) != null)
{
Console.WriteLine(s);
}
}
}
}
using System.IO;
class Test
{
public static void Main()
{
string path = @"c: empMyTest.txt";
FileInfo fi = new FileInfo(path);
if (!fi.Exists)
{
//Create a file to write to.
using (StreamWriter sw = fi.CreateText())
{
sw.WriteLine("Hello");
sw.WriteLine("And");
sw.WriteLine("Welcome");
}
}
//Open the file to read from.
using (StreamReader sr = fi.OpenText())
{
string s = "";
while ((s = sr.ReadLine()) != null)
{
Console.WriteLine(s);
}
}
}
}