BackgroundWorker WPF 困难与进度条

Question

我正在开发 WPF、C# 应用程序，我必须读取一个非常大的 CSV 文件并写入数据库。这个过程需要很长时间，所以我想至少显示一个进度条，它在接近完成时会变大。

现在，我在顶部有以下代码：

private readonly BackgroundWorker worker = new BackgroundWorker();

然后在循环中我有这个：

worker.WorkerReportsProgress = true;
worker.ReportProgress((100 * i) / 10000);

我有一个这样的私人子：

private void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    prgBar.Value = Math.Min(e.ProgressPercentage, 100);
}

但我没有看到进度条更新或发生任何事情，程序仍然挂起。我做错了吗？

更新：在这里http://msdn.microsoft.com/en-us/library/cc221403%28v=vs.95%29.aspx 尝试了 MSDN 指南，但我不知何故未能使其与该示例一起使用。我当然调整了循环部分。呵呵。它仍然保持空闲状态，没有任何更新。哎呀，我想做的就是得到一个小计数器，每次读取和添加一行时都会增加。

更新代码：

    private BackgroundWorker bw = new BackgroundWorker();

    public Process()
    {


        bw.WorkerReportsProgress = true;
        bw.WorkerSupportsCancellation = true;
        bw.DoWork += new DoWorkEventHandler(bw_DoWork);
        bw.ProgressChanged += new ProgressChangedEventHandler(bw_ProgressChanged);
        bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
    }


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


                // Perform a time consuming operation and report progress.



                int d = 0;
                Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();



                // Set filter for file extension and default file extension 
                dlg.DefaultExt = ".csv";
                dlg.Filter = "CSV File (*.csv)|*.csv";
                dlg.Title = "file";


                // Display OpenFileDialog by calling ShowDialog method 
                Nullable<bool> result = dlg.ShowDialog();
                if (result == true)
                {
                    // Open document 
                    string filename = dlg.FileName;
                    List<String[]> fileContent = new List<string[]>();

                    using (FileStream reader = File.OpenRead(@filename)) // mind the encoding - UTF8
                    using (TextFieldParser parser = new TextFieldParser(reader))
                    {

                        using (SqlConnection conn = new SqlConnection(Classes.PublicVariables.Connection))
                        {

                            parser.Delimiters = new[] { "," };
                            parser.HasFieldsEnclosedInQuotes = true;
                            while (!parser.EndOfData)
                            {

                                    string[] line = parser.ReadFields();
                                    fileContent.Add(line);

                                    SqlCommand comm = QUERYANDPARAMETERS

                                    d += 1;
                                    comm.ExecuteNonQuery();
                                    worker.ReportProgress((d * 10));


                        }
                    }

                }


        }


           private void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
lblCount.Content = "Complete";
    }
    private void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
        this.lblCount.Content = (e.ProgressPercentage.ToString() + "%");
    }

当工人运行时，我得到一个摘录。

 An exception of type 'System.NullReferenceException' occurred inSolution.exe but was not handled in user code

附加信息：对象引用未设置为对象的实例。

更新3

搞定了！我所需要的只是与上面相同的代码，但是：

        if (bw.IsBusy != true)
        {
            bw.RunWorkerAsync();
        }
        else
        {
            bw_DoWork(null, null);
        }

在按钮按下的事件处理程序中。

Answer 1

这不会按原样编译，但应该让您朝着正确的方向开始：

private readonly BackgroundWorker worker
    = new BackgroundWorker { WorkerReportsProgress = true };

public MainWindow()
{
    InitializeComponent();

    worker.DoWork += worker_DoWork;
    worker.ProgressChanged += worker_ProgressChanged;
}

private void worker_DoWork(object sender, DoWorkEventArgs doWorkEventArgs)
{
    // Do some long process, break it up into a loop so you can periodically
    //  call worker.ReportProgress()

    worker.ReportProgress(i);  // Pass back some meaningful value
}

private void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    prgBar.Value = Math.Min(e.ProgressPercentage, 100);
}

Answer 2

是变量i int 吗？如果是，(100 * i) / 10000 的值将返回 0 而 i 。 ReportProgress 方法的参数应该是一个百分比值。你可以把它改成worker.ReportProgress(i);，试试吧。