c# Task啟動帶參數和返回值的函數任務

Task有時候相當於Thread的作用

下面的例子test2 是個帶參數和返回值的函數。

private int test2(object i){
this.Invoke(new Action(()=>{pictureBox1.Visible=true;}));
System.Threading.Thread.Sleep(3000);
MessageBox.Show("hello:"+ i);
this.Invoke(new Action(()=>{pictureBox1.Visible=false;}));
return 0;
}

//測試調用
private void call(){

		//Func<string, string> funcOne = delegate(string s){  return "fff"; };
		object  i=55;
		var t= Task<int>.Factory.StartNew(new Func<object ,int>(test2),i);

}

=下載網站源文件例子========================

HttpClient 引用System.Net.Http

private async Task< int> test2(object i){
this.Invoke(new Action(()=>{pictureBox1.Visible=true;}));

   HttpClient client= new HttpClient();
       var a= await 	client.GetAsync("http://www.baidu.com");
      Task<string> s=  a.Content.ReadAsStringAsync();
      MessageBox.Show (s.Result);
		
		//System.Threading.Thread.Sleep(3000);
		//MessageBox.Show("hello:"+ i);
		this.Invoke(new Action(()=>{pictureBox1.Visible=false;}));
		return 0;
	}
	
	
async 	private  void call(){
		
		//Func<string, string> funcOne = delegate(string s){  return "fff"; };
		object  i=55;
		var t= Task<Task<int>>.Factory.StartNew(new Func<object ,Task<int>>(test2),i);

		
		
		
	}

---------------或者---------

	private async void  test2(){
		this.Invoke(new Action(()=>{pictureBox1.Visible=true;}));		
		HttpClient client= new HttpClient();
		var a= await 	client.GetAsync("http://www.baidu.com");
		Task<string> s=  a.Content.ReadAsStringAsync();
		MessageBox.Show (s.Result);
		this.Invoke(new Action(()=>{pictureBox1.Visible=false;}));

	}
	
	
	private  void call(){
		
		var t= Task.Run(new Action(test2));
                   
                   //相當於
	        //Thread th= new Thread(new ThreadStart(test2));
		//th.Start();

	}