Question

我知道BackgroundWorker会使用无法处理的异常并将其传递给RunWorkerCompleted e.Error属性，并且正确处理异常的方法是检查e.Error != null。

在DoWork事件的方法中，我有几个try catch块，但只有其中一些像FailedOperationException正在工作。如果我的代码试图访问一个类在一个不可用的dll中，抛出FileNotFoundException，这不会被更明亮的FileNotFoundException或Exception捕获块所引发。而不是那样，它转到e.Error的{{1}}属性。

为什么只有部分例外被捕？

代码：

RunWorkerCompleted

try { SqlConnection connection = new SqlConnection(Properties.Settings.Default.CharityConnectionString); String dataSource = connection.DataSource; if (((ActionType)e.Argument) == ActionType.Backup) { try { lblWait.Text = "Starting backup operation ..."; ServerConnection serverConnection = new ServerConnection(dataSource); Server sqlServer = new Server(serverConnection); // The exception is thrown here String originalBackupPath = fileName; BackupDeviceItem backupDevice = new BackupDeviceItem(originalBackupPath, DeviceType.File); Backup backup = new Backup(); backup.Action = BackupActionType.Database; backup.Database = "Charity"; backup.Devices.Add(backupDevice); backup.Initialize = true; backup.Checksum = true; backup.ContinueAfterError = true; backup.Incremental = false; backup.LogTruncation = BackupTruncateLogType.Truncate; backup.SqlBackup(sqlServer); MessageBox.Show("Backup was successfull", "", MessageBoxButtons.OK, MessageBoxIcon.Information); } catch (FileNotFoundException ex) // this catch doesn't work for FileNotFoundException exceptions { MessageBox.Show("Error in operation" + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } catch (FailedOperationException) { MessageBox.Show("Access to the selected folder is denied", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } catch (Exception) // and this catch doesn't work for FileNotFoundException, too { MessageBox.Show("Error in operation", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } } } catch(Exception) { MessageBox.Show("Error in operation", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); }消息“无法加载文件或程序集.Microsoft.SqlServer.ConnectionInfo ”仅显示在FileNotFoundException中。我知道如何通过私有安装程序集来解决此异常。

Answer 1

我的猜测是你有异常错误。您是否正在InnerException中查看e.Error？

此代码按预期工作：

using System;
using System.ComponentModel;
using System.IO;
using System.Threading;

class Program
{
    static void Main(string[] args)
    {
        BackgroundWorker worker = new BackgroundWorker();
        worker.DoWork += (s, e) =>
        {
            try
            {
                throw new FileNotFoundException();
            }
            catch (FileNotFoundException)
            {
                Console.WriteLine("FileNotFoundException caught");
            }
        };

        worker.RunWorkerCompleted += (s, e) =>
        {
            if (e.Error != null)
                Console.WriteLine("RunWorkerCompleted error is {0}", e);
        };

        worker.RunWorkerAsync();
        while (worker.IsBusy)
            Thread.Sleep(1);
    }
}

为什么BackgroundWorder DoWork只捕获一些例外？

1 个答案: