How to wait for the task to getfiles?-CodePudding

private async Task GetImagesFiles(string radarImagesFolder)
        {
            DirectoryInfo lastRadarWrittenFolder = null;

            var tt = new DirectoryInfo(textBoxRadarPath.Text).GetDirectories();
            if (tt.Length > 0)
            {
                lastRadarWrittenFolder = new DirectoryInfo(textBoxRadarPath.Text).GetDirectories()
                   .OrderBy(d => d.CreationTimeUtc).First();
            }

            if (Directory.Exists(radarImagesFolder) && tt.Length > 0)
            {
               radarImages = Directory.GetFiles(lastRadarWrittenFolder.FullName, "*.png");
            }
        }

using it

private async void Completed(object sender, AsyncCompletedEventArgs e, Stopwatch sw, string urlAddress)
{
  await GetImagesFiles(textBoxRadarPath.Text);
}

the problem is in the GetImagesFiles method on it's name GetImagesFiles there is a green line warning :

Severity Code Description Project File Line Suppression State Warning CS1998 This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread. Weather D:\Csharp Projects\Weather\Form1.cs 415 Active

i want to wait to get the files before continue the rest of the code. once radarImages array is not null and it's length is higher then 0 then continue the rest of the code.

CodePudding user response：

There is nothing async in GetImagesFiles, so you can just remove async Task from it. This alligns with suggestion from Task.Run Etiquette Examples: Don't Use Task.Run in the Implementation by Stephen Cleary. Also I would move setter out of the GetImagesFiles with resulting code looking like:

private string[] GetImagesFiles(string radarImagesFolder)
{
    DirectoryInfo lastRadarWrittenFolder = null;

    var tt = new DirectoryInfo(textBoxRadarPath.Text).GetDirectories();
    if (tt.Length > 0)
    {
        lastRadarWrittenFolder = new DirectoryInfo(textBoxRadarPath.Text).GetDirectories()
            .OrderBy(d => d.CreationTimeUtc).First();
    }

    if (Directory.Exists(radarImagesFolder) && tt.Length > 0)
    {
         return Directory.GetFiles(lastRadarWrittenFolder.FullName, "*.png");
    }

    return null;
}

And invocation:

private async void Completed(object sender, AsyncCompletedEventArgs e, Stopwatch sw, string urlAddress)
{
    var result = await Task.Run(GetImagesFiles(textBoxRadarPath.Text));
    if(result != null)
    {
        radarImages = result;
    }
}

P.S.

Though returning null as marker can be a code smell but for brevity and due to lack of knowledge about language version you are using I've went with this approach.