c# 将一个长耗时任务改成task

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public Task<ObservableCollection<WaterFallDataSource2>> InitalrenderSourceandBrush2(int width)         {             Stopwatch w = new Stopwatch();             w.Start();             points3.Clear();             int wavelength = GlobalStorage.BigWaves.Length;             int allRows = wavelength / width;             w.Stop();             Debug.WriteLine("w.ElapsedMilliseconds:" + w.ElapsedMilliseconds);             Debug.WriteLine("allRows:" + allRows);             if (allRows > 0)             {                 Parallel.For(0, _pagesize, (lk) =>                 {                     ObservableCollection<DataPoint3> dataPoints = new ObservableCollection<DataPoint3>();                     for (byte j = 0; j < 150; j++)                     {                         for (short i = 0; i < width; i++)                         {                             DataPoint3 dataPoint = new DataPoint3() { VariableX = i, VariableY = j };                             dataPoint.Type = GetColorIndex2(GlobalStorage.BigWaves[lk * width + i][j]);                             dataPoints.Add(dataPoint);                         }                     }                     WaterFallDataSource2 waterFallDataSource = new WaterFallDataSource2();                     waterFallDataSource.DataPoints = dataPoints;                     waterFallDataSource.BrushInfo = brushes;                     waterFallDataSource.Index = lk;                     waterFallDataSource.Width = width;                     waterFallDataSource.StartTime = BeatWaveDataConversionExtension.WaveDotToDateTime(BeatInfoCache.BeatInfos.ElementAt(lk * width).R).ToString();                     points3.Add(waterFallDataSource);                 });                 return Task.FromResult<ObservableCollection<WaterFallDataSource2>>(points3.OrderBy(p => p.Index).ToObservableCollection<WaterFallDataSource2>());             }             else             {                 ObservableCollection<DataPoint3> dataPoints = new ObservableCollection<DataPoint3>();                 WaterFallDataSource2 waterFallDataSource = new WaterFallDataSource2();                 for (byte j = 0; j < 150; j++)                 {                     for (short i = 0; i < wavelength; i++)                     {                         short value = GlobalStorage.BigWaves[i][j];                         DataPoint3 dataPoint = new DataPoint3() { VariableX = i, VariableY = j };                         dataPoint.Type = GetColorIndex2(value);                         dataPoints.Add(dataPoint);                     }                 }                 waterFallDataSource.DataPoints = dataPoints;                 waterFallDataSource.BrushInfo = brushes;                 waterFallDataSource.Index = 0;                 waterFallDataSource.Width = width;                 points3.Add(waterFallDataSource);                 return Task.FromResult<ObservableCollection<WaterFallDataSource2>>(points3);             }         }

调用 

 var reuslt = await _stTrendController.InitalrenderSourceandBrush2((int)firstrowgrid.ActualWidth - 27);