C# File类常用方法

File 类

　　提供用于创建、复制、删除、移动和打开文件的静态方法，并协助创建 FileStream 对象。　　

　1. File.Exists ——  确定指定的文件是否存在。

　　　public static bool Exists(string path)

string curFile = @"c:\temp\test.txt";

Console.WriteLine(File.Exists(curFile) ? "File exists." : "File does not exist.");

　2. File.AppendAllText 方法 —— 将指定的字符串追加到文件中，如果文件还不存在则创建该文件。

　　　public static void AppendAllText(string path,string contents)

using System;

using System.IO;

using System.Text;



class Test

{

    public static void Main()

    {

        string path = @"c:\temp\MyTest.txt";



        // This text is added only once to the file.

        if (!File.Exists(path))

        {

            // Create a file to write to.

            string createText = "Hello and Welcome" + Environment.NewLine;

            File.WriteAllText(path, createText);

        }



        // This text is always added, making the file longer over time

        // if it is not deleted.

        string appendText = "This is extra text" + Environment.NewLine;

        File.AppendAllText(path, appendText);



        // Open the file to read from.

        string readText = File.ReadAllText(path);

        Console.WriteLine(readText);

    }

}

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　　void public static void AppendAllText(string path,string contents,Encoding encoding)

using System;

using System.IO;

using System.Text;



class Test

{

    public static void Main()

    {

        string path = @"c:\temp\MyTest.txt";



        // This text is added only once to the file.

        if (!File.Exists(path))

        {

            // Create a file to write to.

            string createText = "Hello and Welcome" + Environment.NewLine;

            File.WriteAllText(path, createText, Encoding.UTF8);

        }



        // This text is always added, making the file longer over time

        // if it is not deleted.

        string appendText = "This is extra text" + Environment.NewLine;

        File.AppendAllText(path, appendText, Encoding.UTF8);



        // Open the file to read from.

        string readText = File.ReadAllText(path);

        Console.WriteLine(readText);

    }

}

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　3. File.ReadAllText 方法 —— 打开一个文本文件，将文件的所有行读入一个字符串，然后关闭该文件。

　　public static string ReadAllText(string path)

using System;

using System.IO;

using System.Text;



class Test

{

    public static void Main()

    {

        string path = @"c:\temp\MyTest.txt";



        // This text is added only once to the file.

        if (!File.Exists(path))

        {

            // Create a file to write to.

            string createText = "Hello and Welcome" + Environment.NewLine;

            File.WriteAllText(path, createText);

        }



        // This text is always added, making the file longer over time

        // if it is not deleted.

        string appendText = "This is extra text" + Environment.NewLine;

        File.AppendAllText(path, appendText);



        // Open the file to read from.

        string readText = File.ReadAllText(path);

        Console.WriteLine(readText);

    }

}

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　　public static string ReadAllText(string path,Encoding encoding)

　　

using System;

using System.IO;

using System.Text;



class Test

{

    public static void Main()

    {

        string path = @"c:\temp\MyTest.txt";



        // This text is added only once to the file.

        if (!File.Exists(path))

        {

            // Create a file to write to.

            string createText = "Hello and Welcome" + Environment.NewLine;

            File.WriteAllText(path, createText, Encoding.UTF8);

        }



        // This text is always added, making the file longer over time

        // if it is not deleted.

        string appendText = "This is extra text" + Environment.NewLine;

        File.AppendAllText(path, appendText, Encoding.UTF8);



        // Open the file to read from.

        string readText = File.ReadAllText(path);

        Console.WriteLine(readText);

    }

}

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　4. File.ReadAllLines 方法 —— 打开一个文本文件，将文件的所有行都读入一个字符串数组，然后关闭该文件。

　　public static string[] ReadAllLines(string path)

using System;

using System.IO;

class Test

{

    public static void Main()

    {

        string path = @"c:\temp\MyTest.txt";



        // This text is added only once to the file.

        if (!File.Exists(path))

        {

            // Create a file to write to.

            string[] createText = { "Hello", "And", "Welcome" };

            File.WriteAllLines(path, createText);

        }



        // This text is always added, making the file longer over time

        // if it is not deleted.

        string appendText = "This is extra text" + Environment.NewLine;

        File.AppendAllText(path, appendText);



        // Open the file to read from.

        string[] readText = File.ReadAllLines(path);

        foreach (string s in readText)

        {

            Console.WriteLine(s);

        }

    }

}

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　　public static string[] ReadAllLines(string path,Encoding encoding)

using System;

using System.IO;

using System.Text;



class Test

{

    public static void Main()

    {

        string path = @"c:\temp\MyTest.txt";



        // This text is added only once to the file.

        if (!File.Exists(path))

        {

            // Create a file to write to.

            string[] createText = { "Hello", "And", "Welcome" };

            File.WriteAllLines(path, createText, Encoding.UTF8);

        }



        // This text is always added, making the file longer over time

        // if it is not deleted.

        string appendText = "This is extra text" + Environment.NewLine;

        File.AppendAllText(path, appendText, Encoding.UTF8);



        // Open the file to read from.

        string[] readText = File.ReadAllLines(path, Encoding.UTF8);

        foreach (string s in readText)

        {

            Console.WriteLine(s);

        }

    }

}

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　5. File.WriteAllText 方法 —— 创建一个新文件，在文件中写入内容，然后关闭文件。 如果目标文件已存在，则覆盖该文件。

　　public static void WriteAllText(string path,string contents)　　

using System;

using System.IO;

using System.Text;



class Test

{

    public static void Main()

    {

        string path = @"c:\temp\MyTest.txt";



        // This text is added only once to the file.

        if (!File.Exists(path))

        {

            // Create a file to write to.

            string createText = "Hello and Welcome" + Environment.NewLine;

            File.WriteAllText(path, createText);

        }



        // This text is always added, making the file longer over time

        // if it is not deleted.

        string appendText = "This is extra text" + Environment.NewLine;

        File.AppendAllText(path, appendText);



        // Open the file to read from.

        string readText = File.ReadAllText(path);

        Console.WriteLine(readText);

    }

}

View Code

　　public static void WriteAllText(string path,string contents,Encoding encoding)

using System;

using System.IO;

using System.Text;



class Test

{

    public static void Main()

    {

        string path = @"c:\temp\MyTest.txt";



        // This text is added only once to the file.

        if (!File.Exists(path))

        {

            // Create a file to write to.

            string createText = "Hello and Welcome" + Environment.NewLine;

            File.WriteAllText(path, createText, Encoding.UTF8);

        }



        // This text is always added, making the file longer over time

        // if it is not deleted.

        string appendText = "This is extra text" + Environment.NewLine;

        File.AppendAllText(path, appendText, Encoding.UTF8);



        // Open the file to read from.

        string readText = File.ReadAllText(path);

        Console.WriteLine(readText);

    }

}

View Code

　6. File.WriteAllLines 方法 —— 创建一个新文件，在其中写入一个或多个字符串，然后关闭该文件。

　　public static void WriteAllLines(string path,string[] contents)

using System;

using System.IO;

class Test

{

    public static void Main()

    {

        string path = @"c:\temp\MyTest.txt";



        // This text is added only once to the file.

        if (!File.Exists(path))

        {

            // Create a file to write to.

            string[] createText = { "Hello", "And", "Welcome" };

            File.WriteAllLines(path, createText);

        }



        // This text is always added, making the file longer over time

        // if it is not deleted.

        string appendText = "This is extra text" + Environment.NewLine;

        File.AppendAllText(path, appendText);



        // Open the file to read from.

        string[] readText = File.ReadAllLines(path);

        foreach (string s in readText)

        {

            Console.WriteLine(s);

        }

    }

}

View Code

　　public static void WriteAllLines(string path,string[] contents,Encoding encoding)

using System;

using System.IO;

using System.Text;



class Test

{

    public static void Main()

    {

        string path = @"c:\temp\MyTest.txt";



        // This text is added only once to the file.

        if (!File.Exists(path))

        {

            // Create a file to write to.

            string[] createText = { "Hello", "And", "Welcome" };

            File.WriteAllLines(path, createText, Encoding.UTF8);

        }



        // This text is always added, making the file longer over time

        // if it is not deleted.

        string appendText = "This is extra text" + Environment.NewLine;

        File.AppendAllText(path, appendText, Encoding.UTF8);



        // Open the file to read from.

        string[] readText = File.ReadAllLines(path, Encoding.UTF8);

        foreach (string s in readText)

        {

            Console.WriteLine(s);

        }

    }

}

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　7.1. File.Create 方法 —— 在指定路径中创建或覆盖文件。

　　public static FileStream Create(string path)

using System;

using System.IO;

using System.Text;



class Test

{

    public static void Main()

    {

        string path = @"c:\temp\MyTest.txt";



        try

        {



            // Delete the file if it exists.

            if (File.Exists(path))

            {

                // Note that no lock is put on the

                // file and the possibility exists

                // that another process could do

                // something with it between

                // the calls to Exists and Delete.

                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());

        }

    }

}

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　7.2 File.Copy 方法 —— 将现有文件复制到新文件。

　　public static void Copy(string sourceFileName,string destFileName) 将现有文件复制到新文件。 不允许覆盖同名的文件。

string sourceDir = @"c:\current";

string backupDir = @"c:\archives\2008";



try

{

    string[] picList = Directory.GetFiles(sourceDir, "*.jpg");

    string[] txtList = Directory.GetFiles(sourceDir, "*.txt");



    // Copy picture files.

    foreach (string f in picList)

    {

        // Remove path from the file name.

        string fName = f.Substring(sourceDir.Length + 1);



        // Use the Path.Combine method to safely append the file name to the path.

        // Will overwrite if the destination file already exists.

        File.Copy(Path.Combine(sourceDir, fName), Path.Combine(backupDir, fName), true);

    }



    // Copy text files.

    foreach (string f in txtList)

    {



        // Remove path from the file name.

        string fName = f.Substring(sourceDir.Length + 1);



        try

        {

            // Will not overwrite if the destination file already exists.

            File.Copy(Path.Combine(sourceDir, fName), Path.Combine(backupDir, fName));

        }



        // Catch exception if the file was already copied.

        catch (IOException copyError)

        {

            Console.WriteLine(copyError.Message);

        }

    }



    // Delete source files that were copied.

    foreach (string f in txtList)

    {

        File.Delete(f);

    }

    foreach (string f in picList)

    {

        File.Delete(f);

    }

}



catch (DirectoryNotFoundException dirNotFound)

{

    Console.WriteLine(dirNotFound.Message);

}

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　　public static void Copy(string sourceFileName,string destFileName,bool overwrite)

string sourceDir = @"c:\current";

string backupDir = @"c:\archives\2008";



try

{

    string[] picList = Directory.GetFiles(sourceDir, "*.jpg");

    string[] txtList = Directory.GetFiles(sourceDir, "*.txt");



    // Copy picture files.

    foreach (string f in picList)

    {

        // Remove path from the file name.

        string fName = f.Substring(sourceDir.Length + 1);



        // Use the Path.Combine method to safely append the file name to the path.

        // Will overwrite if the destination file already exists.

        File.Copy(Path.Combine(sourceDir, fName), Path.Combine(backupDir, fName), true);

    }



    // Copy text files.

    foreach (string f in txtList)

    {



        // Remove path from the file name.

        string fName = f.Substring(sourceDir.Length + 1);



        try

        {

            // Will not overwrite if the destination file already exists.

            File.Copy(Path.Combine(sourceDir, fName), Path.Combine(backupDir, fName));

        }



        // Catch exception if the file was already copied.

        catch (IOException copyError)

        {

            Console.WriteLine(copyError.Message);

        }

    }



    // Delete source files that were copied.

    foreach (string f in txtList)

    {

        File.Delete(f);

    }

    foreach (string f in picList)

    {

        File.Delete(f);

    }

}



catch (DirectoryNotFoundException dirNotFound)

{

    Console.WriteLine(dirNotFound.Message);

}

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　7.3 File.Move 方法 —— 将指定文件移到新位置，并提供指定新文件名的选项。　

public static void Move(string sourceFileName,string destFileName)

using System;

using System.IO;



class Test 

{

    public static void Main() 

    {

        string path = @"c:\temp\MyTest.txt";

        string path2 = @"c:\temp2\MyTest.txt";

        try 

        {

            if (!File.Exists(path)) 

            {

                // This statement ensures that the file is created,

                // but the handle is not kept.

                using (FileStream fs = File.Create(path)) {}

            }



            // Ensure that the target does not exist.

            if (File.Exists(path2))    

            File.Delete(path2);



            // Move the file.

            File.Move(path, path2);

            Console.WriteLine("{0} was moved to {1}.", path, path2);



            // See if the original exists now.

            if (File.Exists(path)) 

            {

                Console.WriteLine("The original file still exists, which is unexpected.");

            } 

            else 

            {

                Console.WriteLine("The original file no longer exists, which is expected.");

            }            



        } 

        catch (Exception e) 

        {

            Console.WriteLine("The process failed: {0}", e.ToString());

        }

    }

}

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　7.4 File.Delete 方法 ——删除指定的文件。

　　public static void Delete(string path)

string sourceDir = @"c:\current";

string backupDir = @"c:\archives\2008";



try

{

    string[] picList = Directory.GetFiles(sourceDir, "*.jpg");

    string[] txtList = Directory.GetFiles(sourceDir, "*.txt");



    // Copy picture files.

    foreach (string f in picList)

    {

        // Remove path from the file name.

        string fName = f.Substring(sourceDir.Length + 1);



        // Use the Path.Combine method to safely append the file name to the path.

        // Will overwrite if the destination file already exists.

        File.Copy(Path.Combine(sourceDir, fName), Path.Combine(backupDir, fName), true);

    }



    // Copy text files.

    foreach (string f in txtList)

    {



        // Remove path from the file name.

        string fName = f.Substring(sourceDir.Length + 1);



        try

        {

            // Will not overwrite if the destination file already exists.

            File.Copy(Path.Combine(sourceDir, fName), Path.Combine(backupDir, fName));

        }



        // Catch exception if the file was already copied.

        catch (IOException copyError)

        {

            Console.WriteLine(copyError.Message);

        }

    }



    // Delete source files that were copied.

    foreach (string f in txtList)

    {

        File.Delete(f);

    }

    foreach (string f in picList)

    {

        File.Delete(f);

    }

}



catch (DirectoryNotFoundException dirNotFound)

{

    Console.WriteLine(dirNotFound.Message);

}

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