c# - 如何独立于数据加载 UI

Question

我正在使用 C# 和网络服务器中的数据库创建一个应用程序。从网络服务器访问数据时，它非常慢，并且在加载数据之前表单也会挂起。有没有办法先加载表单，然后稍后的数据？

Answer 1

解决这个问题的常用方法是使用 BackgroundWorker类。

public void InitBackgroundWorker()
{
    backgroundWorker.DoWork += YourLongRunningMethod;
    backgroundWorker.RunWorkerCompleted += UpdateTheWholeUi;

    backgroundWorker.WorkerSupportsCancellation = true; // optional

    // these are also optional
    backgroundWorker.WorkerReportsProgress = true;
    backgroundWorker.ProgressChanged += UpdateProgressBar;
}

// This could be in a button click, or simply on form load
if (!backgroundWorker.IsBusy)
{
    backgroundWorker.RunWorkerAsync(); // Start doing work on background thread
}

// ...

private void YourLongRunningMethod(object sender, DoWorkEventArgs e)
{
    var worker = sender as BackgroundWorker;

    if(worker != null)
    {
        // Do work here...
        // possibly in a loop (easier to do checks below if you do)

        // Optionally check (while doing work):
        if (worker.CancellationPending == true)
        {
            e.Cancel = true;
            break; // If you were in a loop, you could break out of it here...
        }
        else
        {
            // Optionally update
            worker.ReportProgress(somePercentageAsInt);
        }

        e.Result = resultFromCalculations; // Supports any object type...
    }
}

private void UpdateProgressBar(object sender, ProgressChangedEventArgs e)
{
    int percent = e.ProgressPercentage;
    // Todo: Update UI
}

private void UpdateTheWholeUi(object sender, RunWorkerCompletedEventArgs e)
{
    if (e.Cancelled)
    {
        // Todo: Update UI
    }
    else if (e.Error != null)
    {
        string errorMessage = e.Error.Message;
        // Todo: Update UI
    }
    else
    {
        object result = e.Result;
        // Todo: Cast the result to the correct object type,
        //       and update the UI
    }
}