使用任务，“索引超出范围”;和IsCompleted过早返回true

我正在尝试测试我对"Windows Store"c#中任务的理解(和学习)。我做了一个多任务应用程序，它包含几个进度条和模拟任务，这些任务在不同的时间段内从1数到100。它最终将成为多线程文件解析器的基础。

我有一个任务处理任务"parseFiles"，它通过检查计数器循环遍历任务队列列表，直到它们全部完成。

无论如何，当这个程序运行时，我在"parseFiles"任务的任务处理for循环中随机获得索引超出范围变化的第一次机会异常。循环计数器i不知何故被设置为一个可能大于3的值，尽管for循环显然只将i设置为最大2。

发生的另一件奇怪的事情是，parsers[]中的"解析"任务有时会返回IsCompleted的真值，即使它们还没有开始。

你知道是什么导致了这些奇怪的bug吗?我做错什么了吗?

我也很乐意接受任何关于更健壮或更简单的排队和处理解析任务的方法的建议，因为它可能会修复这两个错误。

代码如下:

namespace TaskTest
{
public sealed partial class MainPage : Page
{
    testFile[] fileList;
    public MainPage()
    {
        this.InitializeComponent();
        fileList = new testFile[10];
        for(int j=0; j<10; j++){
            fileList[j] = new testFile();
        }
    }
    private static void parseFile(testFile file, IProgress<int> progress)
    {
        progress.Report(0);
        file.parse(progress);
    }
    public Task parseFiles(IProgress<int>[] progresses) {
        int nParsers = 3;
        int nParsers = 3;
        if (nParsers > fileList.Length)
        {
            nParsers = fileList.Length;
        }
        Task[] parsers = new Task[nParsers];
        Boolean parseCompleted = false;
        Task.Run(() =>
            {
                //Do the parsing
                int fileCounter = -1;
                Boolean startedLast = false;
                Boolean[] finalTasksDone = new Boolean[nParsers];
                while (!parseCompleted)
                {
                    for(int i=0; i<=(nParsers - 1); i++){
                        if (!startedLast && (parsers[i] == null || parsers[i].IsCompleted))
                        {
                            fileCounter++;
                            Debug.WriteLine("Task " + i + " completed. Starting new Task " + i + " to parse file #" + fileCounter);
                            if (fileCounter == fileList.Length - 1) { startedLast = true; }
                            Action<testFile, Progress<int>> parseAction = parseFile;
                            parsers[i] = Task.Factory.StartNew(() => parseFile(fileList[fileCounter], progresses[i]));
                        }
                        else
                        {
                            if (startedLast && parsers[i].IsCompleted)
                            {
                                finalTasksDone[i] = true;
                            }
                        }
                    }
                    int finishedCounter = 0;
                    for (int i = 0; i <= (nParsers - 1); i++)
                    {
                        if (finalTasksDone[i])
                        {
                            finishedCounter++;
                        }
                    }
                    if (finishedCounter >= nParsers)
                    {
                        parseCompleted = true;
                    }
                }
            });
        return null;
    }

    public class testFile{
        public async void parse(IProgress<int> progress){
            Random random = new Random();
            int simDelay = 1;
            int simFileLength = random.Next(50, 100);
            Debug.WriteLine("Starting file with length: " + simFileLength);
            for(int j=0; j<simFileLength; j++){
                await Task.Delay(TimeSpan.FromSeconds(simDelay));
                int percentProgress = (int) (((double) j/ (double) simFileLength) * 100);
                progress.Report(percentProgress);
            }
        }
    }
    private void button_Click(object sender, RoutedEventArgs e)
    {
        IProgress<int>[] progresses = new Progress<int>[3];
        progresses[0] = new Progress<int>(ReportProgress1);
        progresses[1] = new Progress<int>(ReportProgress2);
        progresses[2] = new Progress<int>(ReportProgress3);
        parseFiles(progresses);
    }
    private void ReportProgress1(int value)
    {
        pBar1.Value = value;
    }
    private void ReportProgress2(int value)
    {
        pBar2.Value = value;
    }
    private void ReportProgress3(int value)
    {
        pBar3.Value = value;
    }
}

}

这是一个典型运行的日志。根据这一点，大多数任务甚至在IsCompleted返回true之前都没有开始。

Task 0 completed. Starting new Task 0 to parse file #0
Task 1 completed. Starting new Task 1 to parse file #1
Task 2 completed. Starting new Task 2 to parse file #2
A first chance exception of type 'System.IndexOutOfRangeException' occurred in TaskTest.exe
Additional information: Index was outside the bounds of the array.
A first chance exception of type 'System.IndexOutOfRangeException' occurred in  TaskTest.exe
Additional information: Index was outside the bounds of the array.
Task 1 completed. Starting new Task 1 to parse file #3
Task 2 completed. Starting new Task 2 to parse file #4
A first chance exception of type 'System.IndexOutOfRangeException' occurred in TaskTest.exe
Additional information: Index was outside the bounds of the array.
Starting file with length: 73
Starting file with length: 83
Task 2 completed. Starting new Task 2 to parse file #5
A first chance exception of type 'System.IndexOutOfRangeException' occurred in TaskTest.exe
Additional information: Index was outside the bounds of the array.
Task 2 completed. Starting new Task 2 to parse file #6
A first chance exception of type 'System.IndexOutOfRangeException' occurred in TaskTest.exe
Additional information: Index was outside the bounds of the array.
Task 1 completed. Starting new Task 1 to parse file #7
Task 2 completed. Starting new Task 2 to parse file #8
Starting file with length: 78
Task 1 completed. Starting new Task 1 to parse file #9
A first chance exception of type 'System.IndexOutOfRangeException' occurred in TaskTest.exe
Additional information: Index was outside the bounds of the array.
A first chance exception of type 'System.IndexOutOfRangeException' occurred in TaskTest.exe
Additional information: Index was outside the bounds of the array.
The program '[7372] TaskTest.exe' has exited with code 1 (0x1).