C# 多背景辅助角色

我正在尝试设置多个BackgroundWorker来做工作，不忙的时候开始做下一点工作。我似乎无法让它们正常工作。我有以下代码。

当我将FilesToProcess设置为等于或小于MaxThreads时，它可以完美运行，尽管如果我将其提高，应用程序会冻结。

我确信这是一件简单的事情，但我就是看不到它。

using System;
using System.ComponentModel;
using System.Threading;
using System.Windows.Forms;
namespace bgwtest
{
    public partial class Form1 : Form
    {
        private const int MaxThreads = 20;
        private const int FilesToProcess = 21;
        private BackgroundWorker[] threadArray = new BackgroundWorker[MaxThreads];
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1Load(object sender, EventArgs e)
        {
            InitializeBackgoundWorkers();
        }
        private void InitializeBackgoundWorkers()
        {
            for (var f = 0; f < MaxThreads; f++)
            {
                threadArray[f] = new BackgroundWorker();
                threadArray[f].DoWork += new DoWorkEventHandler(BackgroundWorkerFilesDoWork);
                threadArray[f].RunWorkerCompleted += new RunWorkerCompletedEventHandler(BackgroundWorkerFilesRunWorkerCompleted);
                threadArray[f].WorkerReportsProgress = true;
                threadArray[f].WorkerSupportsCancellation = true;
            }
        }
        private void button1_Click(object sender, EventArgs e)
        {
            for (var f = 0; f < FilesToProcess; f++)
            {
                var fileProcessed = false;
                while (!fileProcessed)
                {
                    for (var threadNum = 0; threadNum < MaxThreads; threadNum++)
                    {
                        if (!threadArray[threadNum].IsBusy)
                        {
                            Console.WriteLine("Starting Thread: {0}", threadNum);
                            threadArray[threadNum].RunWorkerAsync(f);
                            fileProcessed = true;
                            break;
                        }
                    }
                    if (!fileProcessed)
                    {
                        Thread.Sleep(50);
                    }
                }
            }
        }
        private void BackgroundWorkerFilesDoWork(object sender, DoWorkEventArgs e)
        {
            ProcessFile((int)e.Argument);
            e.Result = (int)e.Argument;
        }
        private static void ProcessFile(int file)
        {
            Console.WriteLine("Processing File: {0}", file);
        }
        private void BackgroundWorkerFilesRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Error != null)
            {
                MessageBox.Show(e.Error.Message);
            }
            Console.WriteLine("Processed File: {0}", (int)e.Result);
        }
    }
}