Accessing the return value of Task on the same line as await-CodePudding

I had a method SplitInto2DArray that turned a File objects representing a CSV file into a File2DArray class.

File2DArray is a simple class that contains an array for Headers and a 2D array for the body.

public class File2DArray
{
    public string[] Headers;
    public string[][] Content;
}

To turn an array of File objects into File2DArray objects I did: Files.Select(File => File.SplitInto2DArray().Content

However I made SplitInto2DArray into an async function as it was blocking the thread with numerous large CSV files. When I did this I had to change the Select function but I ran into a problem.

.Select(async File => await File.SplitInto2DArray().Content

SplitInto2DArray no longer returns a File2DArray but a Task<File2DArray> which doesn't have the property Content.

I could turn it into a multiline lambda but I am interested if there is a way of accessing the output of an await Task<T> on the same line as the await.

CodePudding user response：

Try Files.Select(async File => (await File.SplitInto2DArray()).Content)

There is a pair of parentheses containing await File.SplitInto2DArray().

While the await keyword blocks the current thread until the async function finish and return, the Task<File2DArray> becomes File2DArray.

Maybe it's not an accurate explanation but it should work.

CodePudding user response：

You can use System.Linq.Async nuget package to get nice extensions for IAsyncEnumerable

PM> Install-Package System.Linq.Async

And your code will look like

var contents = await Files.ToAsyncEnumerable()
    .SelectAwait(async file => await file.SplitInto2DArray())
    .Select(array => array.Content)
    .ToListAsync();