了解如何获取你希望读取和/或写入的文件
可以在
使用选取器打开文件和文件夹
中了解如何使用文件选取器获取文件。
这里介绍了如何在应用的本地文件夹中创建一个文件。 如果文件存在，我们将替换它。
// Create sample file; replace if exists.
Windows.Storage.StorageFolder storageFolder =
Windows.Storage.ApplicationData.Current.LocalFolder;
Windows.Storage.StorageFile sampleFile =
await storageFolder.CreateFileAsync("sample.txt",
Windows.Storage.CreationCollisionOption.ReplaceExisting);
// MainPage.h
#include <winrt/Windows.Storage.h>
Windows::Foundation::IAsyncAction ExampleCoroutineAsync()
// Create a sample file; replace if exists.
Windows::Storage::StorageFolder storageFolder{ Windows::Storage::ApplicationData::Current().LocalFolder() };
co_await storageFolder.CreateFileAsync(L"sample.txt", Windows::Storage::CreationCollisionOption::ReplaceExisting);
// Create a sample file; replace if exists.
StorageFolder^ storageFolder = ApplicationData::Current->LocalFolder;
concurrency::create_task(storageFolder->CreateFileAsync("sample.txt", CreationCollisionOption::ReplaceExisting));
' Create sample file; replace if exists.
Dim storageFolder As StorageFolder = Windows.Storage.ApplicationData.Current.LocalFolder
Dim sampleFile As StorageFile = Await storageFolder.CreateFileAsync("sample.txt", CreationCollisionOption.ReplaceExisting)
下面介绍了如何使用 StorageFile 类在磁盘上写入可写文件。 每种写入文件（除非你在创建后立即写入文件）的方法的常见第一步是使用 StorageFolder.GetFileAsync 获取文件。
Windows.Storage.StorageFolder storageFolder =
Windows.Storage.ApplicationData.Current.LocalFolder;
Windows.Storage.StorageFile sampleFile =
await storageFolder.GetFileAsync("sample.txt");
// MainPage.h
#include <winrt/Windows.Storage.h>
Windows::Foundation::IAsyncAction ExampleCoroutineAsync()
Windows::Storage::StorageFolder storageFolder{ Windows::Storage::ApplicationData::Current().LocalFolder() };
auto sampleFile{ co_await storageFolder.CreateFileAsync(L"sample.txt", Windows::Storage::CreationCollisionOption::ReplaceExisting) };
// Process sampleFile
StorageFolder^ storageFolder = ApplicationData::Current->LocalFolder;
create_task(storageFolder->GetFileAsync("sample.txt")).then([](StorageFile^ sampleFile)
// Process file
Dim storageFolder As StorageFolder = Windows.Storage.ApplicationData.Current.LocalFolder
Dim sampleFile As StorageFile = Await storageFolder.GetFileAsync("sample.txt")
将文本写入文件
通过调用 FileIO.WriteTextAsync 方法，将文本写入文件 。
await Windows.Storage.FileIO.WriteTextAsync(sampleFile, "Swift as a shadow");
// MainPage.h
#include <winrt/Windows.Storage.h>
Windows::Foundation::IAsyncAction ExampleCoroutineAsync()
Windows::Storage::StorageFolder storageFolder{ Windows::Storage::ApplicationData::Current().LocalFolder() };
auto sampleFile{ co_await storageFolder.GetFileAsync(L"sample.txt") };
// Write text to the file.
co_await Windows::Storage::FileIO::WriteTextAsync(sampleFile, L"Swift as a shadow");
StorageFolder^ storageFolder = ApplicationData::Current->LocalFolder;
create_task(storageFolder->GetFileAsync("sample.txt")).then([](StorageFile^ sampleFile)
//Write text to a file
create_task(FileIO::WriteTextAsync(sampleFile, "Swift as a shadow"));
Await Windows.Storage.FileIO.WriteTextAsync(sampleFile, "Swift as a shadow")
使用缓冲区将字节写入文件（2 步）
首先，调用 CryptographicBuffer.ConvertStringToBinary 以获取你想要写入文件的字节（基于字符串）的缓冲区 。
var buffer = Windows.Security.Cryptography.CryptographicBuffer.ConvertStringToBinary(
"What fools these mortals be", Windows.Security.Cryptography.BinaryStringEncoding.Utf8);
// MainPage.h
#include <winrt/Windows.Security.Cryptography.h>
#include <winrt/Windows.Storage.h>
#include <winrt/Windows.Storage.Streams.h>
Windows::Foundation::IAsyncAction ExampleCoroutineAsync()
Windows::Storage::StorageFolder storageFolder{ Windows::Storage::ApplicationData::Current().LocalFolder() };
auto sampleFile{ co_await storageFolder.GetFileAsync(L"sample.txt") };
// Create the buffer.
Windows::Storage::Streams::IBuffer buffer{
Windows::Security::Cryptography::CryptographicBuffer::ConvertStringToBinary(
L"What fools these mortals be", Windows::Security::Cryptography::BinaryStringEncoding::Utf8)};
// The code in step 2 goes here.
StorageFolder^ storageFolder = ApplicationData::Current->LocalFolder;
create_task(storageFolder->GetFileAsync("sample.txt")).then([](StorageFile^ sampleFile)
// Create the buffer
IBuffer^ buffer = CryptographicBuffer::ConvertStringToBinary
("What fools these mortals be", BinaryStringEncoding::Utf8);
Dim buffer = Windows.Security.Cryptography.CryptographicBuffer.ConvertStringToBinary(
"What fools these mortals be",
Windows.Security.Cryptography.BinaryStringEncoding.Utf8)
然后，通过调用 FileIO.WriteBufferAsync 方法，将字节从缓冲区写入文件 。
await Windows.Storage.FileIO.WriteBufferAsync(sampleFile, buffer);
co_await Windows::Storage::FileIO::WriteBufferAsync(sampleFile, buffer);
StorageFolder^ storageFolder = ApplicationData::Current->LocalFolder;
create_task(storageFolder->GetFileAsync("sample.txt")).then([](StorageFile^ sampleFile)
// Create the buffer
IBuffer^ buffer = CryptographicBuffer::ConvertStringToBinary
("What fools these mortals be", BinaryStringEncoding::Utf8);
// Write bytes to a file using a buffer
create_task(FileIO::WriteBufferAsync(sampleFile, buffer));
Await Windows.Storage.FileIO.WriteBufferAsync(sampleFile, buffer)
使用流将文本写入文件（4 步）
首先，调用 StorageFile.OpenAsync 方法打开文件。 打开操作完成后，它将返回文件的内容流。
var stream = await sampleFile.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite);
// MainPage.h
#include <winrt/Windows.Storage.h>
#include <winrt/Windows.Storage.Streams.h>
Windows::Foundation::IAsyncAction ExampleCoroutineAsync()
Windows::Storage::StorageFolder storageFolder{ Windows::Storage::ApplicationData::Current().LocalFolder() };
auto sampleFile{ co_await storageFolder.GetFileAsync(L"sample.txt") };
Windows::Storage::Streams::IRandomAccessStream stream{ co_await sampleFile.OpenAsync(Windows::Storage::FileAccessMode::ReadWrite) };
// The code in step 2 goes here.
StorageFolder^ storageFolder = ApplicationData::Current->LocalFolder;
create_task(storageFolder->GetFileAsync("sample.txt")).then([](StorageFile^ sampleFile)
create_task(sampleFile->OpenAsync(FileAccessMode::ReadWrite)).then([sampleFile](IRandomAccessStream^ stream)
// Process stream
Dim stream = Await sampleFile.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite)
接下来，通过从 stream 调用 IRandomAccessStream.GetOutputStreamAt 方法获取输出流 。 如果你使用的是 C#，则将其附在 using 语句中以管理输出流的生存期 。 如果你使用的是 C++/WinRT，则可以通过将其附在块中，或者通过在使用结束时将其设置为 nullptr 来控制其生存期。
using (var outputStream = stream.GetOutputStreamAt(0))
// We'll add more code here in the next step.
stream.Dispose(); // Or use the stream variable (see previous code snippet) with a using statement as well.
Windows::Storage::Streams::IOutputStream outputStream{ stream.GetOutputStreamAt(0) };
// The code in step 3 goes here.
// Add to "Process stream" in part 1
IOutputStream^ outputStream = stream->GetOutputStreamAt(0);
Using outputStream = stream.GetOutputStreamAt(0)
' We'll add more code here in the next step.
End Using
现在，添加此代码（如果你使用的是 C#，在现有 using 语句中），以通过创建一个新的 DataWriter 对象和调用 DataWriter.WriteString 方法写入输出流 。
using (var dataWriter = new Windows.Storage.Streams.DataWriter(outputStream))
dataWriter.WriteString("DataWriter has methods to write to various types, such as DataTimeOffset.");
Windows::Storage::Streams::DataWriter dataWriter;
dataWriter.WriteString(L"DataWriter has methods to write to various types, such as DataTimeOffset.");
// The code in step 4 goes here.
// Added after code from part 2
DataWriter^ dataWriter = ref new DataWriter(outputStream);
dataWriter->WriteString("DataWriter has methods to write to various types, such as DataTimeOffset.");
Dim dataWriter As New DataWriter(outputStream)
dataWriter.WriteString("DataWriter has methods to write to various types, such as DataTimeOffset.")
最后，添加此代码（如果你使用的是 C#，在内部 using 语句中）以使用 DataWriter.StoreAsync 将文本保存到你的文件并使用 IOutputStream.FlushAsync 关闭该流 。
await dataWriter.StoreAsync();
await outputStream.FlushAsync();
dataWriter.StoreAsync();
outputStream.FlushAsync();
// Added after code from part 3
dataWriter->StoreAsync();
outputStream->FlushAsync();
Await dataWriter.StoreAsync()
Await outputStream.FlushAsync()
向文件进行写入的最佳做法
有关其他详细信息和最佳做法指南，请参阅。
从文件读取
下面介绍了如何使用 StorageFile 类在磁盘上从文件进行读取。 每种从文件读取的方法的常见第一步是使用 StorageFolder.GetFileAsync 获取文件。
Windows.Storage.StorageFolder storageFolder =
Windows.Storage.ApplicationData.Current.LocalFolder;
Windows.Storage.StorageFile sampleFile =
await storageFolder.GetFileAsync("sample.txt");
Windows::Storage::StorageFolder storageFolder{ Windows::Storage::ApplicationData::Current().LocalFolder() };
auto sampleFile{ co_await storageFolder.GetFileAsync(L"sample.txt") };
// Process file
StorageFolder^ storageFolder = ApplicationData::Current->LocalFolder;
create_task(storageFolder->GetFileAsync("sample.txt")).then([](StorageFile^ sampleFile)
// Process file
Dim storageFolder As StorageFolder = Windows.Storage.ApplicationData.Current.LocalFolder
Dim sampleFile As StorageFile = Await storageFolder.GetFileAsync("sample.txt")
从文件读取文本
通过调用 FileIO.ReadTextAsync 方法，从文件读取文本 。
string text = await Windows.Storage.FileIO.ReadTextAsync(sampleFile);
Windows::Foundation::IAsyncOperation<winrt::hstring> ExampleCoroutineAsync()
Windows::Storage::StorageFolder storageFolder{ Windows::Storage::ApplicationData::Current().LocalFolder() };
auto sampleFile{ co_await storageFolder.GetFileAsync(L"sample.txt") };
co_return co_await Windows::Storage::FileIO::ReadTextAsync(sampleFile);
StorageFolder^ storageFolder = ApplicationData::Current->LocalFolder;
create_task(storageFolder->GetFileAsync("sample.txt")).then([](StorageFile^ sampleFile)
return FileIO::ReadTextAsync(sampleFile);
Dim text As String = Await Windows.Storage.FileIO.ReadTextAsync(sampleFile)
通过使用缓冲区从文件读取文本（2 步）
首先，调用 FileIO.ReadBufferAsync 方法。
var buffer = await Windows.Storage.FileIO.ReadBufferAsync(sampleFile);
Windows::Storage::StorageFolder storageFolder{ Windows::Storage::ApplicationData::Current().LocalFolder() };
auto sampleFile{ co_await storageFolder.GetFileAsync(L"sample.txt") };
Windows::Storage::Streams::IBuffer buffer{ co_await Windows::Storage::FileIO::ReadBufferAsync(sampleFile) };
// The code in step 2 goes here.
StorageFolder^ storageFolder = ApplicationData::Current->LocalFolder;
create_task(storageFolder->GetFileAsync("sample.txt")).then([](StorageFile^ sampleFile)
return FileIO::ReadBufferAsync(sampleFile);
}).then([](Streams::IBuffer^ buffer)
// Process buffer
Dim buffer = Await Windows.Storage.FileIO.ReadBufferAsync(sampleFile)
然后，使用 DataReader 对象先读取缓冲区的长度，然后读取其内容。
using (var dataReader = Windows.Storage.Streams.DataReader.FromBuffer(buffer))
string text = dataReader.ReadString(buffer.Length);
auto dataReader{ Windows::Storage::Streams::DataReader::FromBuffer(buffer) };
winrt::hstring bufferText{ dataReader.ReadString(buffer.Length()) };
// Add to "Process buffer" section from part 1
auto dataReader = DataReader::FromBuffer(buffer);
String^ bufferText = dataReader->ReadString(buffer->Length);
Dim dataReader As DataReader = Windows.Storage.Streams.DataReader.FromBuffer(buffer)
Dim text As String = dataReader.ReadString(buffer.Length)
使用流从文件读取文本（4 步）
通过调用 StorageFile.OpenAsync 方法，为你的文件打开流。 操作完成后，它将返回文件的内容流。
var stream = await sampleFile.OpenAsync(Windows.Storage.FileAccessMode.Read);
Windows::Storage::StorageFolder storageFolder{ Windows::Storage::ApplicationData::Current().LocalFolder() };
auto sampleFile{ co_await storageFolder.GetFileAsync(L"sample.txt") };
Windows::Storage::Streams::IRandomAccessStream stream{ co_await sampleFile.OpenAsync(Windows::Storage::FileAccessMode::Read) };
// The code in step 2 goes here.
StorageFolder^ storageFolder = ApplicationData::Current->LocalFolder;
create_task(storageFolder->GetFileAsync("sample.txt")).then([](StorageFile^ sampleFile)
create_task(sampleFile->OpenAsync(FileAccessMode::Read)).then([sampleFile](IRandomAccessStream^ stream)
// Process stream
Dim stream = Await sampleFile.OpenAsync(Windows.Storage.FileAccessMode.Read)
获取稍后要使用的流的大小。
ulong size = stream.Size;
uint64_t size{ stream.Size() };
// The code in step 3 goes here.
// Add to "Process stream" from part 1
UINT64 size = stream->Size;
Dim size = stream.Size
通过调用 IRandomAccessStream.GetInputStreamAt 方法获取输入流 。 将其放到 using 语句中以管理流的生存期。 调用 GetInputStreamAt 时指定 0，以将位置设置在流的开头。
using (var inputStream = stream.GetInputStreamAt(0))
// We'll add more code here in the next step.
Windows::Storage::Streams::IInputStream inputStream{ stream.GetInputStreamAt(0) };
Windows::Storage::Streams::DataReader dataReader{ inputStream };
// The code in step 4 goes here.
// Add after code from part 2
IInputStream^ inputStream = stream->GetInputStreamAt(0);
auto dataReader = ref new DataReader(inputStream);
Using inputStream = stream.GetInputStreamAt(0)
' We'll add more code here in the next step.
End Using
最后，将此代码添加到现有的 using 语句中以在流上获取 DataReader 对象，然后通过调用 DataReader.LoadAsync 和 DataReader.ReadString 读取文本。
using (var dataReader = new Windows.Storage.Streams.DataReader(inputStream))
uint numBytesLoaded = await dataReader.LoadAsync((uint)size);
string text = dataReader.ReadString(numBytesLoaded);
unsigned int cBytesLoaded{ co_await dataReader.LoadAsync(size) };
winrt::hstring streamText{ dataReader.ReadString(cBytesLoaded) };
// Add after code from part 3
create_task(dataReader->LoadAsync(size)).then([sampleFile, dataReader](unsigned int numBytesLoaded)
String^ streamText = dataReader->ReadString(numBytesLoaded);
Dim dataReader As New DataReader(inputStream)
Dim numBytesLoaded As UInteger = Await dataReader.LoadAsync(CUInt(size))
Dim text As String = dataReader.ReadString(numBytesLoaded)
向文件进行写入的最佳做法
