C# 知识点集锦（二）异步入门，在其他线程更新UI，异常处理

一。多线程创建

            Task.Factory.StartNew(
                delegate
                {
                    TimeConsumingTask();
                }
                );

            Task.Factory.StartNew(
                () =>
                {
                    TimeConsumingTask();
                }
            );
            Task.Run(
                () =>
                {
                    TimeConsumingTask2();

                });

            ThreadPool.QueueUserWorkItem(o =>
            {
                TimeConsumingTask2();
            });

二。在其他线程中修改UI

方式一:

            this.label1.Invoke((MethodInvoker)delegate
            {
                this.label1.Text = "Time is UP";
            });

方式二：使用Dispatcher

先在UI线程中
dispatcher = Dispatcher.CurrentDispatcher;
在工作线程中

            dispatcher.Invoke(() =>
                {
                    this.label1.Text = "Time is UP2";

                });

 方式三：使用async await 和Progress类

        private async void button1_Click(object sender, EventArgs e)
        {
            var progress = new Progress<string>((o)=>this.label1.Text=o+"%");
            await Task.Factory.StartNew(()=>LongWork(progress), TaskCreationOptions.LongRunning);

        }

        private void LongWork(IProgress<string> progress)
        {
            for (var i = 1; i <= 100; i++)
            {
                Task.Delay(100).Wait();
                progress.Report(i.ToString());
            }
        }

三 线程中异常的处理

情况1.以上面为例，将async函数的内容使用try包裹起来，异步方法中在合适的情况下抛出异常。

        private async void button1_Click(object sender, EventArgs e)
        {
            button1.Enabled = false;
            try
            {
                var progress = new Progress<string>((o) => this.label1.Text = o + "%");
                await Task.Factory.StartNew(() => LongWork(progress), TaskCreationOptions.LongRunning);
            }
            catch (Exception ex)
            {
                
                this.label1.Text="Failed : "+ex.Message;
            }
            button1.Enabled = true;


        }

        private void LongWork(IProgress<string> progress)
        {

            for (var i = 1; i <= 100; i++)
            {
                if (i >= 40)
                    throw new Exception("Over 40 ,there is  always an Exception。。");
                Task.Delay(100).Wait();
                progress.Report(i.ToString());
            }
        }

 处理异常例子2

        private async void button1_Click(object sender, EventArgs e)
        {

            try
            {
                this.label1.Text = await JustDO();
            }
            catch (Exception ex)
            {
                
                this.label1.Text=ex.Message;
            }
        }

        private  Task<string> JustDO()
        {
            return Task.Run(() =>
            {
                Task.Delay(TimeSpan.FromSeconds(4)).Wait();
                throw new Exception("oooops");
                return Task.FromResult("OK");
            });

        }