Question

对于我的项目，我对C＃和WPF有点新意。我过去在做什么的小图片。我编写了一个程序来备份我的MS SQL数据库。我们的想法是，在它自己的流程线程中启动每个备份过程。这很完美！我使用以下命令启动进程和线程：

...
string db_name = Convert.ToString(dataReader.GetValue(0));
var t = new Thread(() => BackupProcess(ServerName, SQLinstance, BackupPath, db_name));
t.Start();

现在，当一切都结束时，我想像“如果最后一个线程结束，而不是像XY这样的东西”监视这样做的最佳方式是什么？ THX回答

Answer 1

现在几乎没有理由直接处理线程。使用Task Parallel Library和async-await非常容易。

您可以启动任务数量，保留任务的引用，并在需要时等待/等待它。

Task backupTask = Task.Run(() => BackupProcess(ServerName, SQLinstance, BackupPath, db_name));
Task someOtherTask = Task.Run(() => SomeOtherWork(anyParameter));
...
//Later at some point    
await Task.WhenAll(new []{backupTask, someOtherTask });
//At this point all tasks has been completed
//Do whatever you need to execute after all tasks finished

注意：BackupProcess如果使用asynchronous API of your data provider而不使用Task.Run而使ThreadPool线程在那里等待，则可以使CountDownEvent异步。

如果你仍然想要使用线程方法（你不应该这样做），你可以使用Thread.Join进行同步，或者ObservableCollection<Model> collection = new ObservableCollection<Model>(); ObservableCollection<Model> filteredCollection = new ObservableCollection<Model>(from item in collection where item.ID >0 && item.ID < 10 orderby item.ID select item);使用所有已启动的线程。

Answer 2

看看TPL和ContinueWith。它非常优雅，应符合您的要求。

Action<string> action =
            (str) =>
                Console.WriteLine("Task={0}, str={1}, Thread={2}", Task.CurrentId, str, Thread.CurrentThread.ManagedThreadId);

// Creating a sequence of action tasks (that return no result).
Console.WriteLine("Creating a sequence of action tasks (that return no result)");
Task.Factory.StartNew(() => action("alpha"))
            .ContinueWith(antecendent => action("beta"))        // Antecedent data is ignored
            .ContinueWith(antecendent => action("gamma"))
            .Wait();

来自：https://msdn.microsoft.com/de-de/library/dd321405(v=vs.110).aspx

ContinueWith（）也可以帮助您处理执行任务时发生的异常。

Answer 3

好的，我真的不明白它的方式。正如您所看到的，我将在Point中的Loop中开始一个新任务：＆＃34; while（dataReader.Read（））＆＃34;。我的服务器中有尽可能多的数据库，循环将重复。我不知道下次我将拥有多少个DB。最后，当所有任务完成后，我想转到＆＃34; DoSomething＆＃34;方法。有没有人可以告诉我它的方式。这让我很疯狂（这个东西）。： - ）

    private async void ReadDatabase()
    {
        string errorMSG01 = "...";
        string errorMSG02 = "...";
        string captionMSG = "...

        string BackupPath = txtBakPath.Text;
        string ServerName = txtSqlServer.Text;
        string SQLinstance = cmbSqlInst.SelectedItem.ToString();

        MessageBoxButtons buttons = MessageBoxButtons.OK;

        if (String.IsNullOrEmpty(txtBakPath.Text))
        {
            System.Windows.Forms.MessageBox.Show(errorMSG01, captionMSG, buttons, MessageBoxIcon.Error, MessageBoxDefaultButton.Button1);
        }
        else if (!Directory.Exists(BackupPath))
        {
            System.Windows.Forms.MessageBox.Show(errorMSG02, captionMSG, buttons, MessageBoxIcon.Error, MessageBoxDefaultButton.Button1);
        }
        else
        {
            string connetionString = null;
            SqlConnection connection;
            SqlCommand command;
            string sql = null;
            SqlDataReader dataReader;
            connetionString = ("Data Source=DPC-OHEINRICH\\NETZWERKLABOR; Integrated Security=True;");
            sql = "Select * from Sys.Databases";
            connection = new SqlConnection(connetionString);
            try
            {
                connection.Open();
                command = new SqlCommand(sql, connection);
                dataReader = command.ExecuteReader();
                StatusPrinter(0x0003, null);
                CreateLogfile(BackupPath);
                DeleteOldBakFiles();
                while (dataReader.Read())
                {
                    string db_name = Convert.ToString(dataReader.GetValue(0));
                    Task backupTask = Task.Run(() => BackupProcess(ServerName, SQLinstance, BackupPath, db_name));
                }
                dataReader.Close();
                command.Dispose();
                connection.Close();
            }
            catch (Exception ex)
            {
                lblStatusMessage.Content = Convert.ToString(ex.Message);
            }
        }
    }

    private void BackupProcess(string ServerName, string SQLinstance, string BackupPath, string db_name)
    {
        DateTime today = DateTime.Now;
        string todayformat = string.Format("{0:G}", today);
        string BakFileDate = todayformat.Replace(".", "").Replace(" ", "").Replace(":", "");
        string ReportBakFile = BackupPath + "\\" + db_name + "_db_" + BakFileDate + @".bak'";

        if (db_name != "tempdb")
        {
            string connetionString = null;
            SqlConnection connection;
            SqlCommand command;
            string sql = null;
            SqlDataReader dataReader;
            connetionString = ("Data Source="+ServerName+"\\"+SQLinstance+"; Integrated Security=True;");
            sql = @"BACKUP DATABASE " + db_name + @" TO DISK = '" + BackupPath + "\\" + db_name + "_db_" + BakFileDate + @".bak'";
            connection = new SqlConnection(connetionString);
            try
            {
                connection.Open();
                command = new SqlCommand(sql, connection);
                dataReader = command.ExecuteReader();
                dataReader.Close();
                command.Dispose();
                connection.Close();
            }
            catch (Exception ex)
            {
                System.Windows.Forms.MessageBox.Show(ex.Message);
            }
            this.Dispatcher.Invoke(new Action(() => this.WriteLogile(1, ReportBakFile)));
            this.Dispatcher.Invoke(new Action(() => this.StatusPrinter(0x0004, db_name)));
        }
    }
    public void DoSomething()
    {
        //we are done...
    }

C＃WPF线程监控（如果所有创建的线程都已结束）

3 个答案: