C# - Threading using Task

之前在【C# Threading Finial】裡面已經把目前我所知道 Threading 跟 UI 配合的方法 demo 了一次，
上次同事告訴我說在 .net 4.0 (VS2010) 裡面提供了一個新的方式 Task 來寫 Threading ，
所以我就把上次【C# Threading Finial】裡面的程式拿來改成用 Task 的方式，
測試了一下，的確是簡單了許多，
不過規矩還是一樣，跟 UI 的互動還是得交給主執行緒，
所以還是得用 Invoke 的方式來呼叫，
其實我覺得比較麻煩的還是跟 UI 的互動，其他的倒是還好，
接下來就來看看上次那個程式怎麼修改成 Task 的方式吧！
首先原來的 btnThreadingQuery_Click 就變成下面這樣啦！
改成用 Task.Factory.StartNew 的方式來呼叫 QueryMain()

private void btnThreadingQuery_Click(object sender, EventArgs e)

{

    //ThreadPool.QueueUserWorkItem(new WaitCallback(QueryMain));

    Task.Factory.StartNew(() =>

    {

        QueryMain();

    });

}

然後主程式主要的修改如下：

• 之前 waitHandles 都不要。
• 然後 object param 也不需要。
• 原本用 ThreadPool.QueueUserWorkItem 改成用 Task.Factory.StartNew 。
• 最後 WaitHandle.WaitAll 變成 Task.WaitAll 。

大致上就是這樣，程式碼少了很多變得很簡潔，
整段的程式碼如下：

//private void QueryMain(object param)

private void QueryMain()

{

    //waitHandles = new List<WaitHandle>();

    Cursor tmpCursor = this.Cursor;

    Label[] labels = { lblThreadingDuration, lblThreadingTable1Count,

                            lblThreadingTable1Duration, lblThreadingTable2Count,

                            lblThreadingTable2Duration };

    ResetLabel(labels);

    try

    {

        this.Invoke(new UpdateButtonEnableHandler(UpdateButtonEnable),

            new object[] { btnThreadingQuery, false });

        this.Invoke(new UpdateFormCursorHandler(UpdateFormCursor),

            new object[] { Cursors.WaitCursor });

        CalcTime calcTime = new CalcTime();

        //waitHandles.Add(new AutoResetEvent(false));

        //object param1 = new object[] { "table1", lblThreadingTable1Count,

            //lblThreadingTable1Duration, calcTime};

            //lblThreadingTable1Duration, calcTime, waitHandles[waitHandles.Count()-1]};

        //ThreadPool.QueueUserWorkItem(

            //new WaitCallback(QueryTableByThreading), param1);

        var task1 = Task.Factory.StartNew(() =>

        {

            QueryTableByThreading("table1", lblThreadingTable1Count, lblThreadingTable1Duration, calcTime);

        });

        //waitHandles.Add(new AutoResetEvent(false));

        //object param2 = new object[] { "table2 ", lblThreadingTable2Count,

            //lblThreadingTable2Duration, calcTime};

            //lblThreadingTable2Duration, calcTime, waitHandles[waitHandles.Count()-1]};

        //ThreadPool.QueueUserWorkItem(

            //new WaitCallback(QueryTableByThreading), param2);

        var task2 = Task.Factory.StartNew(() =>

        {

            QueryTableByThreading("table2", lblThreadingTable2Count, lblThreadingTable2Duration, calcTime);

        });

        //WaitHandle.WaitAll(waitHandles.ToArray());

        Task.WaitAll(task1, task2);

        //lblThreadingDuration.Text = calcTime.Duration();

        this.Invoke(new UpdateLabelTextHandler(UpdateLabelText),

            new object[] { lblThreadingDuration, calcTime.Duration() });

    }

    finally

    {

        this.Invoke(new UpdateFormCursorHandler(UpdateFormCursor),

            new object[] { tmpCursor });

        this.Invoke(new UpdateButtonEnableHandler(UpdateButtonEnable),

            new object[] { btnThreadingQuery, true });

    }

}

然後 QueryTableByThreading 就恢復成原來我們熟悉的寫法，
不用再去解 Object Param 了！程式如下：

//private void QueryTableByThreading(object param)

private void QueryTableByThreading(string table, Label count, Label duration, CalcTime ct)

{

    //object[] oa = (object[])param;

    //string table = oa[0].ToString();

    //Label count = (Label)oa[1];

    //Label duration = (Label)oa[2];

    //CalcTime ct = (CalcTime)oa[3];

    //AutoResetEvent are = (AutoResetEvent)oa[4];

    DataTable dt = DBUtility.GetTableFromDB(table);

    string time = ct.Duration();

    this.Invoke(new UpdateLabelTextHandler(UpdateLabelText),

        new object[] { count, dt.Rows.Count.ToString("N") });

    this.Invoke(new UpdateLabelTextHandler(UpdateLabelText),

        new object[] { duration, time });

    //are.Set();

}

不知道甚麼時候可以簡化跟 UI 的互動？