WinForm防止程式「沒有回應」的小技巧, Application.DoEvents, no response

Application.DoEvents Sample.cs

/// <summary>
/// 使用 DoEvents 防止沒有回應
/// </summary>
private void button1_Click(object sender, EventArgs e)
{
    //## 使用 DoEvents 防止沒有回應
    for (int i = 0; i <= 999999; i++)
    {
        // ProcessDataPiece[i]
        label1.Text = i.ToString();

        // 處理目前在訊息佇列中的所有Windows訊息。
        Application.DoEvents();
    }
}

/// <summary>
/// 這段碼將沒有回應
/// </summary>
private void button2_Click(object sender, EventArgs e)
{
    //## 這段碼將沒有回應
    for (int i = 0; i <= 999999; i++)
    {
        // ProcessDataPiece[i]
        label2.Text = i.ToString();
    }
}

BackgroundWorker Sample.cs

/// <summary>
/// 使用 BackgroundWorker 防止沒有回應
/// </summary>

// resource
BackgroundWorker _bgWorker;
class _bgWorker_UserState // use to exchange information between main thread and background-worker thread.
{
    // arguments
    public int total;
    // user state
    public int currentState;
    // result
    //...
}

private void button3_Click(object sender, EventArgs e)
{
    //## 使用 BackgroundWorker 防止沒有回應
    _bgWorker = new BackgroundWorker();
    _bgWorker.WorkerReportsProgress = true;
    _bgWorker.DoWork += _bgWorker_DoWork;
    _bgWorker.RunWorkerCompleted += _bgWorker_RunWorkerCompleted;
    _bgWorker.ProgressChanged += _bgWorker_ProgressChanged;

    //# construct "UserState" to exchange information between main thread and and _bgWorker.
    _bgWorker_UserState userState = new _bgWorker_UserState();
    userState.total = 999999; // set up arguments

    // go
    _bgWorker.RunWorkerAsync(userState);
}

void _bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    // parese UserState
    _bgWorker_UserState userState = (_bgWorker_UserState)e.UserState;

    // show progress [e.ProgressPercentage]
    label3.Text = userState.currentState.ToString();
}

void _bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    // parese Result
    _bgWorker_UserState userState = (_bgWorker_UserState)e.Result;

    // show progress
    label3.Text = "已完成";
}

void _bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
    //# parese Argument
    _bgWorker_UserState userState = (_bgWorker_UserState)e.Argument;

    //# go 
    DateTime checkPoint = DateTime.Now;
    for (int i = 0; i <= userState.total; i++)
    {
        // ProcessDataPiece[i]
        userState.currentState = i; // update running state

        // report current progress
        if (DateTime.Now.Subtract(checkPoint).TotalSeconds >= 1.0) // report interval of 1 second.
        {
            int percentProgress = (int)((double)i / (double)userState.total * 100.0);
            _bgWorker.ReportProgress(percentProgress, userState);
        }
    }
    
    // success
    // take result and will pass to event: _bgWorker_RunWorkerCompleted
    e.Result = userState;
}

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