Does the .net framework provides async methods for working with the file-system?
Solution 1
Does the .net framework has an async built-in library/assembly which allows to work with the file system
Yes. There are async methods for working with the file system but not for the helper methods on the static File
type. They are on FileStream
.
So, there's no File.ReadAllBytesAsync
but there's FileStream.ReadAsync
, etc. For example:
byte[] result;
using (FileStream stream = File.Open(@"C:\file.txt", FileMode.Open))
{
result = new byte[stream.Length];
await stream.ReadAsync(result, 0, (int)stream.Length);
}
Solution 2
It already does it. See for example Using Async for File Access MSDN article.
private async Task WriteTextAsync(string filePath, string text)
{
byte[] encodedText = Encoding.Unicode.GetBytes(text);
using (FileStream sourceStream = new FileStream(filePath,
FileMode.Append, FileAccess.Write, FileShare.None,
bufferSize: 4096, useAsync: true))
{
await sourceStream.WriteAsync(encodedText, 0, encodedText.Length);
};
}
Solution 3
Does the .net framework has an async built-in library/assembly which allows to work with the file system (e.g. File.ReadAllBytes, File.WriteAllBytes)?
Unfortunately, the desktop APIs are a bit spotty when it comes to asynchronous file operations. As you noted, a number of the nice convenience methods do not have asynchronous equivalents. Also missing are asynchronous opening of files (which is especially useful when opening files over a network share).
I'm hoping these APIs will be added as the world moves to .NET Core.
Or do I have to write my own library using the async Methods of StreamReader and StreamWriter?
That's the best approach right now.
Note that when using ReadAsync
/WriteAsync
and friends, you must explicitly open the file for asynchronous access. The only way to do this (currently) is to use a FileStream
constructor overload that takes a bool isAsync
parameter (passing true
) or a FileOptions
parameter (passing FileOptions.Asynchronous
). So you can't use the convenience open methods like File.Open
.
Solution 4
In .NET core (since version 2.0) there are now all the async flavors of corresponding ReadAll/WriteAll/AppendAll methods like:
File.(Read|Write|Append)All(Text|Lines|Bytes)Async
https://docs.microsoft.com/en-us/dotnet/api/system.io.file.readallbytesasync?view=netcore-2.1
Unfortunately, they are still missing from .NET standard 2.0.
Comments
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BendEg almost 2 years
Does the .net framework has an
async
built-in library/assembly which allows to work with the file system (e.g.File.ReadAllBytes
,File.WriteAllBytes
)?Or do I have to write my own library using the
async
Methods ofStreamReader
andStreamWriter
?Something like this would be pretty nice:
var bytes = await File.ReadAllBytes("my-file.whatever");