使用 .NET的IO(5)

查找现有的文件和目录

您还可以使用独立存储文件来搜索现有的目录和文件。请记住，在存储区中，文件名和目录名是相对于虚文件系统的根目录指定的。此外，Windows 文件系统中的文件和目录名不区分大小写。

要搜索某个目录，请使用 IsolatedStorageFile 的 GetDirectoryNames 实例方法。GetDirectoryNames 采用表示搜索模式的字符串。支持使用单字符 (?) 和多字符 (*) 通配符。这些通配符不能出现在名称的路径部分。也就是说，directory1/*ect* 是有效的搜索字符串，而 *ect*/directory2 不是有效的搜索字符串。

要搜索某个文件，请使用 IsolatedStorageFile 的 GetFileNames 实例方法。对应用于 GetDirectoryNames 的搜索字符串中通配符的相同限制也适用于 GetFileNames。

GetDirectoryNames 和 GetFileNames 都不是递归的，即 IsolatedStorageFile 不提供用于列出存储区中所有目录或文件的方法。但是，下面的代码中部分是递归方法的示例。另外还要注意，GetDirectoryNames 和 GetFileNames 只返回找到的项的目录名或文件名。例如，如果找到目录 RootDir/SubDir/SubSubDir 的匹配项，结果数组中将返回 SubSubDir。

FindingExistingFilesAndDirectories 示例

下面的代码示例阐释如何在独立存储区创建文件和目录。首先，检索一个按用户、域和程序集隔离的存储区并放入 isoStore 变量。CreateDirectory 方法用于设置几个不同的目录，IsolatedStorageFileStream 方法在这些目录中创建一些文件。然后，代码依次通过 GetAllDirectories 方法的结果。该方法使用 GetDirectoryNames 来查找当前目录中的所有目录名。这些名称存储在数组中，然后 GetAllDirectories 调用其本身，传入它所找到的每个目录。结果是在数组中返回的所有目录名。然后，代码调用 GetAllFiles 方法。该方法调用 GetAllDirectories 以查找所有目录的名称，然后它检查每个目录以查找使用 GetFileNames 方法的文件。结果返回到数组中用于显示。

 [C#]

using System;

using System.IO;

using System.IO.IsolatedStorage;

using System.Collections;

public class FindingExistingFilesAndDirectories{

   // Retrieves an array of all directories in the store, and 

   // displays the results.

   public static void Main(){

      // This part of the code sets up a few directories and files in the

      // store.

      IsolatedStorageFile isoStore = IsolatedStorageFile.GetStore(IsolatedStorageScope.User | IsolatedStorageScope.Assembly, null, null);

      isoStore.CreateDirectory("TopLevelDirectory");

      isoStore.CreateDirectory("TopLevelDirectory/SecondLevel");

      isoStore.CreateDirectory("AnotherTopLevelDirectory/InsideDirectory");

      new IsolatedStorageFileStream("InTheRoot.txt", FileMode.Create, isoStore);

      new IsolatedStorageFileStream("AnotherTopLevelDirectory/InsideDirectory/HereIAm.txt", FileMode.Create, isoStore);

      // End of setup.

      Console.WriteLine('\r');

      Console.WriteLine("Here is a list of all directories in this isolated store:");

      foreach(string directory in GetAllDirectories("*", isoStore)){

         Console.WriteLine(directory);

      }

      Console.WriteLine('\r');

      // Retrieve all the files in the directory by calling the GetFiles 

      // method.

      Console.WriteLine("Here is a list of all the files in this isolated store:");

      foreach(string file in GetAllFiles("*", isoStore)){

         Console.WriteLine(file);

      }  

   }// End of Main.

   // Method to retrieve all directories, recursively, within a store.

   public static string[] GetAllDirectories(string pattern, IsolatedStorageFile storeFile){

      // Get the root of the search string.

      string root = Path.GetDirectoryName(pattern);

      if (root != "") root += "/";

      // Retrieve directories.

      string[] directories;

      directories = storeFile.GetDirectoryNames(pattern);

      ArrayList directoryList = new ArrayList(directories);

      // Retrieve subdirectories of matches.

      for (int i = 0, max = directories.Length; i < max; i++){

         string directory = directoryList[i] + "/";

         string[] more = GetAllDirectories (root + directory + "*", storeFile);

         // For each subdirectory found, add in the base path.

         for (int j = 0; j < more.Length; j++)

            more[j] = directory + more[j];

         // Insert the subdirectories into the list and 

         // update the counter and upper bound.

         directoryList.InsertRange(i+1, more);

         i += more.Length;

         max += more.Length;

      }

      return (string[])directoryList.ToArray(Type.GetType("System.String"));

   }

   public static string[] GetAllFiles(string pattern, IsolatedStorageFile storeFile){

      // Get the root and file portions of the search string.

      string fileString = Path.GetFileName(pattern);

      string[] files;

      files = storeFile.GetFileNames(pattern);

      ArrayList fileList = new ArrayList(files);

      // Loop through the subdirectories, collect matches, 

      // and make separators consistent.

      foreach(string directory in GetAllDirectories( "*", storeFile))

         foreach(string file in storeFile.GetFileNames(directory + "/" + fileString))

            fileList.Add((directory + "/" + file));

      return (string[])fileList.ToArray(Type.GetType("System.String"));

   }// End of GetFiles.

}

读取和写入文件

使用 IsolatedStorageFileStream 类，有多种方法可以打开存储区中的文件。一旦获得了 IsolatedStorageFileStream 之后，可使用它来获取 StreamReader 或 StreamWriter。使用 StreamReader 和 StreamWriter，您可以像对任何其他文件一样读取和写入存储区中的文件。

ReadingAndWritingToFiles 示例

下面的代码示例获得独立存储区，创建一个名为 TestStore.txt 的文件并将“Hello Isolated Storage”写入文件。然后，代码读取该文件并将结果输出到控制台。

 [C#]

using System;

using System.IO;

using System.IO.IsolatedStorage;

public class ReadingAndWritingToFiles{

   public static int Main(){

      // Get an isolated store for this assembly and put it into an

      // IsolatedStoreFile object.

      IsolatedStorageFile isoStore =  IsolatedStorageFile.GetStore(IsolatedStorageScope.User | IsolatedStorageScope.Assembly, null, null);

      // This code checks to see if the file already exists.

      string[] fileNames = isoStore.GetFileNames("TestStore.txt");

      foreach (string file in fileNames){

         if(file == "TestStore.txt"){

            Console.WriteLine("The file already exists!");

            Console.WriteLine("Type \"StoreAdm /REMOVE\" at the command line to delete all Isolated Storage for this user.");

            // Exit the program.

            return 0;

         }

      }

      writeToFile(isoStore);

      Console.WriteLine("The file \"TestStore.txt\" contains:");

      // Call the readFromFile and write the returned string to the

      //console.

      Console.WriteLine(readFromFile(isoStore));

      // Exit the program.

      return 0;

   }// End of main.

   // This method writes "Hello Isolated Storage" to the file.

   private static void writeToFile(IsolatedStorageFile isoStore){

      // Declare a new StreamWriter.

      StreamWriter writer = null;

      // Assign the writer to the store and the file TestStore.

      writer = new StreamWriter(new IsolatedStorageFileStream("TestStore.txt", FileMode.CreateNew,isoStore));

      // Have the writer write "Hello Isolated Storage" to the store.

      writer.WriteLine("Hello Isolated Storage");

      writer.Close();

      Console.WriteLine("You have written to the file.");

   }// End of writeToFile.

   // This method reads the first line in the "TestStore.txt" file.

   public static String readFromFile(IsolatedStorageFile isoStore){

      // This code opens the TestStore.txt file and reads the string.

      StreamReader reader = new StreamReader(new IsolatedStorageFileStream("TestStore.txt", FileMode.Open,isoStore));

      // Read a line from the file and add it to sb.

      String sb = reader.ReadLine();

      // Close the reader.

      reader.Close();

      // Return the string.

      return sb.ToString();

   }// End of readFromFile.

}

删除文件和目录

您可以删除独立存储文件中的目录和文件。请记住，在存储区中，文件名和目录名是与操作系统相关的（在 Microsoft Windows 系统中通常不区分大小写），并且是根据虚文件系统的根目录具体而定的。

IsolatedStoreFile 类提供了两种删除目录和文件的实例方法：DeleteDirectory 和 DeleteFile。如果尝试删除并不存在的文件和目录，则会引发 IsolatedStorageFileException。如果名称中包含有通配符，则 DeleteDirectory 会引发 IsolatedStorageFileException，而 DeleteFile 将引发 ArgumentException。

如果目录中包含任何文件或子目录，DeleteDirectory 将会失败。在 DeletingFilesAndDirectories 示例的一部分中定义了一个方法，该方法删除目录中的所有内容，然后删除目录本身。同样，您可以自己定义一个接受通配符的 DeleteFiles 方法，该方法可以这样来实现：使用 GetFileNames 方法获取所有匹配文件的列表，然后依次删除每个文件。

DeletingFilesAndDirectories 示例

下面的代码示例先创建若干个目录和文件，然后将它们删除。

 [C#]

using System;

using System.IO.IsolatedStorage;

using System.IO;

public class DeletingFilesDirectories{

   public static void Main(){

      // Get a new isolated store for this user domain and assembly.

      // Put the store into an isolatedStorageFile object.

      IsolatedStorageFile isoStore =  IsolatedStorageFile.GetStore(IsolatedStorageScope.User | IsolatedStorageScope.Domain | IsolatedStorageScope.Assembly, null, null);

      Console.WriteLine("Creating Directories:");

      // This code creates several different directories.

      isoStore.CreateDirectory("TopLevelDirectory");

      Console.WriteLine("TopLevelDirectory");

      isoStore.CreateDirectory("TopLevelDirectory/SecondLevel");

      Console.WriteLine("TopLevelDirectory/SecondLevel");

      // This code creates two new directories, one inside the other.

      isoStore.CreateDirectory("AnotherTopLevelDirectory/InsideDirectory");

      Console.WriteLine("AnotherTopLevelDirectory/InsideDirectory");

      Console.WriteLine();

      // This code creates a few files and places them in the directories.

      Console.WriteLine("Creating Files:");

      // This file is placed in the root.

      IsolatedStorageFileStream isoStream1 = new IsolatedStorageFileStream("InTheRoot.txt", FileMode.Create, isoStore);

      Console.WriteLine("InTheRoot.txt");

      isoStream1.Close();

      // This file is placed in the InsideDirectory.

      IsolatedStorageFileStream isoStream2 = new IsolatedStorageFileStream("AnotherTopLevelDirectory/InsideDirectory/HereIAm.txt", FileMode.Create, isoStore);

      Console.WriteLine("AnotherTopLevelDirectory/InsideDirectory/HereIAm.txt");

      Console.WriteLine();

      isoStream2.Close();

      Console.WriteLine("Deleting File:");

      // This code deletes the HereIAm.txt file.

      isoStore.DeleteFile("AnotherTopLevelDirectory/InsideDirectory/HereIAm.txt");

      Console.WriteLine("AnotherTopLevelDirectory/InsideDirectory/HereIAm.txt"); 

      Console.WriteLine();

      Console.WriteLine("Deleting Directory:");

      // This code deletes the InsideDirectory.

      isoStore.DeleteDirectory("AnotherTopLevelDirectory/InsideDirectory/");

      Console.WriteLine("AnotherTopLevelDirectory/InsideDirectory/");

      Console.WriteLine();

   }// End of main.

}

总结

    上面是VS.NET中.NET中IO的基本概念、示例代码以及访问文件系统的基础方法和流程，大家可以多多实践。有任何建议请MAIL我 [email protected]。

 

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