自定义事件和windows phone访问网站取得数据

    昨天看了一位园友的自定义事件的文章，我以前学习过这方面的内容，但在实际工作中基本没用过自定义事件，前天就边看着，自己写了写代码把这个知识点复习了。下面上代码

　　事件类代码

public class EvevtClass:EventArgs
    {
        public  string State;
        public  string Data;
        public  DateTime Time;
        public EvevtClass(string state, string data)
        {
            this.Time = DateTime.Now;
            this.Data = data;   
            this.State = state;
        }
    }

这上面的代码我是看一位园友写的，但是这其中我有个问题。就是我写的这个类非要继承EventArgs类吗？但是我试了下，如果不继承程序运行效果是一样的。我记得我当时学习事件的时候说是自定义事件类必须继承EventArgs类，如果我不继承呢？还是我记错了。

下面调用事件类

public class NetTask
    {
        public delegate void Dele(NetTask sender, EvevtClass args);
        public delegate void DeleTwo(object o, string str);
        public event DeleTwo Change; 
        public event Dele OnStateChanged;
        public string Data;
        public void StartNetTask(string url)
        {
            bool success = false;
            //int attempt = 0;
            //while (attempt < 3)
            //{
            //    AsyncCallback callBack = null;
            //    ManualResetEvent webRequestWait = new ManualResetEvent(false);
            //    WebRequest request = WebRequest.Create(url);
            //    if (callBack==null)
            //    {
            //        callBack = (ar) =>
            //        {
            //            try
            //            {
            //                WebRequest re = ar.AsyncState as WebRequest;
            //                WebResponse response = re.EndGetResponse(ar);
            //                Stream stream = response.GetResponseStream();
            //                StreamReader reader = new StreamReader(stream);
            //                Data = reader.ReadToEnd();
            //                success = true;
            //                webRequestWait.Set();
            //            }
            //            catch (Exception)
            //            {

            //            }

            //        };
            //    }
            //    request.BeginGetResponse(callBack, request);
            ////Thread.Sleep(9000);
            //    webRequestWait.WaitOne();
            //    if (success)
            //    {
            //        break;
            //    }
            //    attempt++;
            //    Thread.Sleep(1000);
            //}
            WebRequest request = WebRequest.Create(url);
            AsyncCallback callBack = (ar) =>
                {
                    try
                    {
                        WebRequest re = ar.AsyncState as WebRequest;
                        WebResponse response = re.EndGetResponse(ar);
                        Stream stream = response.GetResponseStream();
                        StreamReader reader = new StreamReader(stream);
                        Data = reader.ReadToEnd();
                        success = true;
                    }
                    catch (Exception)
                    {

                    }
                    if (success)
                    {
                        OnStateChanged(this, new EvevtClass("网络连接成功", Data));
                    }
                    else
                    {
                        OnStateChanged(this, new EvevtClass("网络连接失败", "没数据"));
                    }

                };
            request.BeginGetResponse(callBack, request);
            //Thread.Sleep(9000);

                
        }
    }

下面是ViewModel类

public class ViewModel:INotifyPropertyChanged
    {
        string state;
        public string State
        {
            set
            {
                state = value;
                Raise("State");
            }
            get
            {
                return state;
            }

        }
        string data;
        public string Data
        {
            set
            {
                data = value;
                Raise("Data");
            }
            get
            {
                return data;
            }
        }
        ICommand buttomCommand;
        public ICommand Button
        {
            get
            {
                buttomCommand = new DeleCommand((o) =>
                {
                    NetTask net = new NetTask();
                    net.OnStateChanged += new NetTask.Dele(net_OnStateChanged);
                    net.OnStateChanged += new NetTask.Dele(Method);///这行多此一举，是为了加深事件的理解而写
                    net.StartNetTask(o);
                    //State = "state";
                    //Data = "datadatadtaa";
                }
                );
                return buttomCommand;
            }
        }
        void net_OnStateChanged(NetTask sender, EvevtClass args)
        {
            Deployment.Current.Dispatcher.BeginInvoke(() =>
                {
                    State = args.State + args.Time;
                }
                );
        }
        void Method(NetTask sender, EvevtClass args)
        {
            Deployment.Current.Dispatcher.BeginInvoke(() =>
            {
                Data = args.Data;
            }
            );
        }
        public event PropertyChangedEventHandler PropertyChanged;
        void Raise(string name)
        {
            if (PropertyChanged!=null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(name));
            }
        }
    }

实现了ICommand类

public class DeleCommand:ICommand
    {
        public DeleCommand(Action<string> a)
        {
            Del = a;
        }
        public Action<string> Del;
        public bool CanExecute(object parameter)
        {
            return true;
        }

        public event EventHandler CanExecuteChanged;

        public void Execute(object parameter)
        {
            Del(parameter.ToString());
        }
    }

界面

<Grid x:Name="LayoutRoot" Background="Transparent">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Button Content="测试连接" CommandParameter="{Binding ElementName=textbox,Path=Text}" Command="{Binding Button}" Click="Button_Click"></Button>
        <StackPanel  Grid.Row="1">
            <TextBox Name="textbox" Text="http://www.cnblogs.com"></TextBox>
            <StackPanel Orientation="Horizontal">
                <TextBlock FontSize="28">状态：</TextBlock>
                <TextBlock Name="state" Text="{Binding State}"></TextBlock>
            </StackPanel>
            <StackPanel >
                <TextBlock FontSize="28"> 数据:</TextBlock>
                <ScrollViewer Height="500">
                    <TextBlock Text="{Binding Data}" TextWrapping="Wrap" Name="data"></TextBlock>
                </ScrollViewer>
            </StackPanel>
        </StackPanel>
    </Grid>

最后运行效果图

OK完了。希望有明白的人，回答下我的那个疑问！