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
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
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)
IBuffer buffer = await FileIO.ReadBufferAsync(storageFile);
using (DataReader dataReader = DataReader.FromBuffer(buffer))
{
string fileContent = dataReader.ReadString (buffer.Length);
}还可通过流读取文件内容
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
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
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
await storageFile.DeleteAsync()
复制文件
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
StorageFile storageFile1=await storageFile.RenameAsync("sampleRe.txt")
移动文件
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
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
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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