Windows 8 Metro Stype App 学习笔记（五）文件操作

Windows 8 Metro Style App中文件操作都包含在Windows.Storage命名空间中，其中包括StorageFolder,StorageFile,FileIO等类库。

文件对象用StorageFile实现，文件头用StorageFolder实现，下面看下具体的用法及各类库下的属性他方法。

创建文件

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StorageFolder storageFolder=KnownFolders.DocumentsLibrary;

   StorageFile storageFile=await storageFolder.CreateFileAsync("sample.txt",CreationCollisionOption.ReplaceExisting);

KnownFolders提供了系统中常规的文件路径。
CreationCollisionOption提供了创建文件冲突时的操作选项。

FileIO对象负责文件的读/写操作

读取文件

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string fielContent=await FileIO.ReadTextAsync(storageFile);

读取操作包含三种方式：

返回普通文本 ReadTextAsync(storageFile)/ReadTextAsync(storageFile,UnicodeEncoding)(返回指定的文本编码格式)
返回流 ReadBufferAsync(storageFile)

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IBuffer buffer = await FileIO.ReadBufferAsync(storageFile);

 using (DataReader dataReader = DataReader.FromBuffer(buffer))

 {

     string fileContent = dataReader.ReadString (buffer.Length);                   

 }

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还可通过流读取文件内容

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using (IRandomAccessStream readStream = await sampleFile.OpenAsync(FileAccessMode.Read))

                {

                    using (DataReader dataReader = new DataReader(readStream))

                    {

                        uint numBytesLoaded = await dataReader.LoadAsync((uint)readStream.Size);

                        string fileContent = dataReader.ReadString(numBytesLoaded);                     

                    }

                }

返回文本行

ReadLinesAsync(storageFile)/ReadLinesAsync(storageFile,UnicodeEncoding)

 

 

写入文件

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await FileIO.WriteTextAsync(storageFile,content)

    写入文件也包含以下几种操作：
    写入Buffer数据 WriteBufferAsync(IStorage File,IBuffer buffer)
    写入bytes字节数据 WriteBytesAsync（IStorage File,bytes[] byte）
    写入文本行 WriteLinesAsync(IStorageFile File, IIterable(String)) /WriteLinesAsync(IStorageFile File, IIterable(String), UnicodeEncoding)
    写入字符串 WriteTextAsync(IStorageFile File,string content)

通过流写入内容

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using (IRandomAccessStream writeStream = await storageFile.OpenAsync(FileAccessMode.ReadWrite))

                    {                       

                        using (DataWriter dataWriter = new DataWriter(writeStream))

                        {

                            dataWriter.WriteString(userContent);

                            await dataWriter.StoreAsync();

                            await dataWriter.FlushAsync();                          

                        }

                    }

同样也提供追加文本的方法

AppendLinesAsync(IStorageFile, IIterable(String)) /AppendLinesAsync(IStorageFile, IIterable(String), UnicodeEncoding)
AppendTextAsync(IStorageFile, String) /AppendTextAsync(IStorageFile, String, UnicodeEncoding)

删除文件

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await storageFile.DeleteAsync()

复制文件

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StorageFile storageFileCopy = await storageFile.CopyAsync(KnownFolders.DocumentsLibrary, "sample - Copy.txt", NameCollisionOption.ReplaceExisting);

复制文本也有几种方式
   CopyAndReplaceAsync
   CopyAsync(IStorageFolder)
   CopyAsync(IStorageFolder, String FileName)
   CopyAsync(IStorageFolder, String FileName, NameCollisionOption)

重命名文件

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StorageFile storageFile1=await storageFile.RenameAsync("sampleRe.txt")

移动文件

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await storageFile.MoveAsync(StorageFolder NewStorageFolder,string NewFileName);

提到文件操作，不得不说说文件流。
在以前的开发中，我们经常用到的就是文件流、字节数组等操作，在WinRT中有些区别，文件流有 IRandomAccessStream、FileInputStream、FileOutStream、FileRandomAccessStream 等，用IBuffer代替了byte[]。下面看看具体的用法：
获取文件流

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IRandomAccessStream readStream = await sampleFile.OpenAsync(FileAccessMode.Read)

 

FileInputStream inputStream=readStream.GetInputStreamAt(0) as FileInputStream;

 

FileOutputStream outStream=readStream.GetOutputStreamAt(0) as FileOutputStream;

DataReader/DataWriter的用法见上

IBuffer、byte[]、Stream之间的转换

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IBuffer buffer = await FileIO.ReadBufferAsync(sampleFile);

byte[] bytes=WindowsRuntimeBufferExtensions.ToArray(buffer,0,(int)buffer.Length);

Stream stream = WindowsRuntimeBufferExtensions.AsStream(buffer);

还有很多文件操作的场景没有整理，虽然WinRT中提供了很多文件流，但它们的核心用法都是类似 的，希望在后续的不断使用中慢慢接触不同类型流的使用。

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