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使用 .NET的IO(5) Paul_Ni

2024-07-10 13:08:10
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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
getdirectorynamesgetfilenames 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,getdirectorynamesgetfilenames 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 streamreaderstreamwriter,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]([email protected])。
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