Waiting for multiple synchronous tasks to finish

Question

I'm wondering is this the best way to run two tasks in parallel but without using async/await.

public string Export()
{
    var ifcFilePaths = ExportIfcFiles().ToList();
    Task<List<IfcToCsvGraphExportResult>> graphConverterResults = ConvertIfcToGraphData(ifcFilePaths);
    Task<List<IfcToGltfConversionResult>> gltfConverterResults = ConvertIfcToGltfData(ifcFilePaths);
    List<string> folders = _outputFolderPacker.Pack(graphConverterResults.Result, gltfConverterResults.Result).ToList();

    return _zipPacker.Pack(folders);
}

private Task<List<IfcToCsvGraphExportResult>> ConvertIfcToGraphData(List<string> ifcFilePaths)
    => Task.Run(() => _ifcToCsvGraphExporter.Export(ifcFilePaths).ToList());

private Task<List<IfcToGltfConversionResult>> ConvertIfcToGltfData(List<string> ifcFilePaths)
    => Task.Run(() => _ifcToGltfConverter.Convert(ifcFilePaths).ToList());

I want ConvertIfcToGraphData and ConvertIfcToGltfData methods to run in parallel, but on the other hand I want _outputFolderPacker.Pack() method to wait for both results before processing. My issue is I cannot make main Export() method async/await due to some API limitations.

I think you could use `Task.WaitAll()` after running tha tasks and before returning from Export function... — Marco, May 11 '21 at 21:30

score 3 · Accepted Answer · answered May 11 '21 at 21:37

I think you could use Task.WaitAll() after running the tasks and before returning from Export function.

public string Export()
{
    var ifcFilePaths = ExportIfcFiles().ToList();
    Task<List<IfcToCsvGraphExportResult>> graphConverterResults = ConvertIfcToGraphData(ifcFilePaths);
    Task<List<IfcToGltfConversionResult>> gltfConverterResults = ConvertIfcToGltfData(ifcFilePaths);
    
    // This is the missing part
    Task.WaitAll(new[] {graphConverterResults, gltfConverterResults});
    
    List<string> folders = _outputFolderPacker.Pack(graphConverterResults.Result, gltfConverterResults.Result).ToList();

    return _zipPacker.Pack(folders);
}

Some detail can be found on Microsoft docs page: https://learn.microsoft.com/en-us/dotnet/api/system.threading.tasks.task.waitall?view=net-5.0

Probably worth mentioning that both existing and proposed solution will in fact satisfy *"but on the other hand I want _outputFolderPacker.Pack() method to wait for both results before processing."* — trashr0x, May 11 '21 at 21:40

Waiting for multiple synchronous tasks to finish

1 Answers1