CODEWITHSUNDEEP
c#task-parallel-libraryasync-await
VAAA
VAAA

Reputation: 15039

Task ContinuewWith await returning error

I have the following code that uses System.Threading.Tasks

private async void UploadDocument(System.IO.FileInfo fileInfo)
{
    var someTask = await Task.Run<bool>(() =>
    {
        // open input stream
        using (System.IO.FileStream stream = new System.IO.FileStream(FileTextBox.Text, System.IO.FileMode.Open, System.IO.FileAccess.Read))
        {
            using (StreamWithProgress uploadStreamWithProgress = new StreamWithProgress(stream))
            {
                uploadStreamWithProgress.ProgressChanged += uploadStreamWithProgress_ProgressChanged;

                // start service client
                FileTransferWCF.FileTransferServiceClient client = new FileTransferWCF.FileTransferServiceClient();
                //FileTransferClient.FileTransferServiceClient client = new FileTransferClient.FileTransferServiceClient();

                // upload file
                client.UploadFile(fileInfo.Name, fileInfo.Length, uploadStreamWithProgress);

                // close service client
                client.Close();
            }
        }

        return true;

    }).ContinueWith(r =>{
        if(r.Result) LogText("Done!!");
    });

}

If I leave this and try to compile I get:

"Cannot assign void to an implicitly-typed local variable"** in the var someTask

So I then change var someTask to Task someTask but now I get the error:

"Cannot implicitly convert type 'void' to 'System.Threading.Tasks.Task'".

Any clue on how to deal with this?

Upvotes: 0

Views: 2134

Answers (1)

SLaks
SLaks

Reputation: 887453

The await keyword waits for a task to finish and returns the result.

It does not return the task itself.

Since your ContinueWith() doesn't have a result (it returns Task, not Task<T>), your await expression returns void, which obviously cannot be assigned to a variable.

You can simplify your code like this:

await Task.Run(() => {
    using (...) {
        ...
    }
});
LogText("Done!");

Upvotes: 6

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