C# async await 學習筆記1（http://www.cnblogs.com/siso/p/3691059.html）

?提到了ThreadId是一樣的，突然想到在WinForm中，非UI線程是無法直接更新UI線程上的控件的問題。

于是做了如下測試：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading.Tasks;
using System.Threading;namespace WindowsFormsApplication1
{public partial class Form1 : Form{public Form1(){InitializeComponent();}Task<string> LongTimeTask(){tbResult.Text += "LongTimeTask開始:" + DateTime.Now.ToString() + "\r\n";             Task<string> task = new Task<string>(() => { Thread.Sleep(5000); return "這是任務返回值"; });task.Start();tbResult.Text += "LongTimeTask結束:" + DateTime.Now.ToString() + "\r\n";    return task;}async void AsyncCall(){tbResult.Text += "AsyncCall開始：" + DateTime.Now.ToString() + "\r\n";     string result = await LongTimeTask(); //await調用的方法需要返回Task或Task<T>，且調用await所在的方法要有async關鍵字tbResult.Text += "AsyncCall:" + result + "\r\n"; tbResult.Text += "AsyncCall結束：" + DateTime.Now.ToString() + "\r\n"; }   private void button1_Click(object sender, EventArgs e){tbResult.Text += "Main開始：" + DateTime.Now.ToString() + "\r\n";AsyncCall();tbResult.Text += "Main結束：" + DateTime.Now.ToString() + "\r\n";}}
}

　發現，在AsyncCall中，可以直接訪問TextBox（tbResult)，如果對上面的測試覺得沒什么奇怪，大家可以先看下面的代碼。

?

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;namespace WindowsFormsApplication1
{public partial class Form2 : Form{public Form2(){InitializeComponent();}void LongTimeTask(){Thread.Sleep(5000);tbResult.Text += "AsyncCall結束：" + DateTime.Now.ToString() + "\r\n";} private void button1_Click(object sender, EventArgs e){tbResult.Text += "Main開始：" + DateTime.Now.ToString() + "\r\n";Thread t = new Thread(LongTimeTask);t.Start();tbResult.Text += "Main結束：" + DateTime.Now.ToString() + "\r\n";}}
}

運行到?LongTimeTask的tbResult.Text時，提示：線程間操作無效: 從不是創建控件“tbResult”的線程訪問它。

? ? ? 為了能在非UI線程中訪問到UI線程中的控件，于是需作如下修改：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;namespace WindowsFormsApplication1
{public partial class Form2 : Form{delegate void UpdateUIDelegate();UpdateUIDelegate updateUIDelegate;        public Form2(){InitializeComponent();updateUIDelegate = new UpdateUIDelegate(UpdateUI);}void UpdateUI(){if (tbResult.InvokeRequired){tbResult.Invoke(updateUIDelegate);}else{tbResult.Text += "AsyncCall結束：" + DateTime.Now.ToString() + "\r\n";}}void LongTimeTask(){Thread.Sleep(5000);UpdateUI();        } private void button1_Click(object sender, EventArgs e){tbResult.Text += "Main開始：" + DateTime.Now.ToString() + "\r\n";Thread t = new Thread(LongTimeTask);t.Start();tbResult.Text += "Main結束：" + DateTime.Now.ToString() + "\r\n";}}
}

?

轉載于:https://www.cnblogs.com/siso/p/3691494.html

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