确保将事件处理程序附加到ProgressChanged和DoWork之后：
1.从DoWork事件处理程序中删除progressBar1.PerformStep()。
1.然后在ProgressChanged事件处理程序中仅使用progressBar1.Value = e.ProgressPercentage;。

几年前，我写了一个简单的多线程进度条码。希望它能帮助你：

#region Primenumbers
private void btnPrimStart_Click(object sender, EventArgs e)
{
    if (!bgwPrim.IsBusy)
    {
        //Prepare ProgressBar and Textbox
        int temp = (int)nudPrim.Value;
        pgbPrim.Maximum = temp;
        tbPrim.Text = "";

        //Start processing
        bgwPrim.RunWorkerAsync(temp);
    }
}

private void btnPrimCancel_Click(object sender, EventArgs e)
{
    if (bgwPrim.IsBusy)
    {
        bgwPrim.CancelAsync();
    }
}

private void bgwPrim_DoWork(object sender, DoWorkEventArgs e)
{
    int highestToCheck = (int)e.Argument;
    //Get a reference to the BackgroundWorker running this code
    //for Progress Updates and Cancelation checking
    BackgroundWorker thisWorker = (BackgroundWorker)sender;

    //Create the list that stores the results and is returned by DoWork
    List<int> Primes = new List<int>();

    //Check all uneven numbers between 1 and whatever the user choose as upper limit
    for(int PrimeCandidate=1; PrimeCandidate < highestToCheck; PrimeCandidate+=2)
    {
        //Report progress
        thisWorker.ReportProgress(PrimeCandidate);
        bool isNoPrime = false;

        //Check if the Cancelation was requested during the last loop
        if (thisWorker.CancellationPending)
        {
            //Tell the Backgroundworker you are canceling and exit the for-loop
            e.Cancel = true;
            break;
        }

        //Determin if this is a Prime Number
        for (int j = 3; j < PrimeCandidate && !isNoPrime; j += 2)
        {
            if (PrimeCandidate % j == 0)
                isNoPrime = true;
        }

        if (!isNoPrime)
            Primes.Add(PrimeCandidate);
    }

    //Tell the progress bar you are finished
    thisWorker.ReportProgress(highestToCheck);

    //Save Return Value
    e.Result = Primes.ToArray();
}

private void bgwPrim_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    pgbPrim.Value = e.ProgressPercentage;
}

private void bgwPrim_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    pgbPrim.Value = pgbPrim.Maximum;
    this.Refresh();

    if (!e.Cancelled && e.Error == null)
    {
        //Show the Result
        int[] Primes = (int[])e.Result;

        StringBuilder sbOutput = new StringBuilder();

        foreach (int Prim in Primes)
        {
            sbOutput.Append(Prim.ToString() + Environment.NewLine);
        }

        tbPrim.Text = sbOutput.ToString();
    }
    else 
    {
        tbPrim.Text = "Operation canceled by user or Exception";
    }
}
#endregion

通常，当从Alterante线程编写UI元素时，您必须使用Invoke.BackgroundWorker很好，并在创建它的线程（应该是GUI线程）上调用“ReportProgress”和“RunWorkerCompleted”事件，因此您还不必处理多线程的那部分问题。
捕捉任何异常也是很好的，这些异常通常会逃脱DoWork并被吞掉，并在Completed Event Args中将它们暴露给您。吞掉异常是多线程的一个大问题。
核心问题是，你的循环会因为一个异常而中断。在DoWork事件**内部调用progressBar1.PerformStep();**必须抛出一个“CrossThreadException”。BackgroundnWorker会立即结束（由于一个异常）。RunWorker completed事件会在i为初始值时触发。