Reactive Extension

目录：

1、Timer:设定Obervable执行时间间隔。

2、Enumerable to Observable转换

3、Observable to Enumerable 转换

4、zip 匹配的两个序列合并操作，返回一个合并后的值

5、Buffer 缓存集合

6、TimeOut 超出预订时间，取消订阅事件。当超出时间后可以Catch这个异常。

7、Merge 合并两个Observable

8、CombineLatest 最近输入的两个数字相比较

9、Publish 共享订阅事件

10、Interval 订阅事件的时间间隔

11、Group 分组

1、Timer:设定Obervable执行时间间隔。

Subscrible 订阅事件，Dispose 取消订阅的事件。Timer的前一个参数是开始时间，第二个是 时间间隔。

            var observable = Observable.Timer(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(1))
                .Where(x => x % 2 == 0).Select(x => new { First = x, Second = x * x });
            var disposable = observable.Subscribe(a => Console.WriteLine("Value is {0} double Value is {1}", a.First, a.Second), () => Console.WriteLine("Completed"));

            Console.ReadLine();
            disposable.Dispose();

结果

2、Enumerable to Observable转换

IEnumerable<char> c = "abc";
            IObservable<char> observable = c.ToObservable();
            observable.Subscribe(x => Console.WriteLine(x),()=>Console.WriteLine("Completed"));

3、Observable to Enumerable 转换

IObservable<long> observable = Observable.Timer(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(1));
            var enumerable = observable.ToEnumerable();
            foreach (var l in enumerable)
            {
                Console.WriteLine(l);
            }

4、zip 匹配的两个序列合并操作，返回一个合并后的值

 IObservable<int> observable1 = new int[] { 1, 2, 3 }.ToObservable();
            IObservable<int> observable2 = new int[] { 5, 3, 8, 4 }.ToObservable();
            var zip = observable1.Zip(observable2, (x1, x2) => x1 * x2);
            zip.Subscribe(x => Console.WriteLine(x));

5、Buffer 缓存集合

当我集合不断在增加的时候，我需要在增加到一定数量，才执行操作。如下：每过3秒 输出一次结果。

IObservable<long> observable = Observable.Timer(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(1));
            var buffer = observable.Buffer(TimeSpan.FromSeconds(3));
            buffer.Subscribe(x =>
                                 {
                                     Console.WriteLine("after 3 second");
                                     foreach (var l in x)
                                     {
                                         Console.WriteLine("value is {0}", l);
                                     }
                                 });

6、TimeOut 超出预订时间，取消订阅事件。当超出时间后可以Catch这个异常。

 IObservable<long> sequence = Observable.Timer(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(1));
            sequence = sequence.Buffer(3).SelectMany(values => values);
            sequence = sequence.Timeout(TimeSpan.FromSeconds(2));
            IDisposable subscription = sequence.Subscribe(value => Console.WriteLine("Value produced is {0}", value));

这里TimeOut设置了2秒，而Buffer是3秒，也就是要3秒后输出结果，但这时的3秒超出了我们设定的TimeOut，也就取消了这个订阅事件

，什么都不会输出。我们捕获这个异常。

 IObservable<long> sequence = Observable.Timer(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(1));
            sequence = sequence.Buffer(3).SelectMany(values => values);
            sequence = sequence.Timeout(TimeSpan.FromSeconds(2));
            IDisposable subscription = sequence.Subscribe(value => Console.WriteLine("Value produced is {0}", value),
        error => Console.WriteLine("Error occurred [{0}]", error.Message));

对这个异常做处理。

IObservable<long> sequence = Observable.Timer(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(1));
            sequence = sequence.Buffer(3).SelectMany(values => values);
            sequence = sequence.Timeout(TimeSpan.FromSeconds(2)).Catch(new long[] { 1, 3, 5 }.ToObservable());
            IDisposable subscription = sequence.Subscribe(value => Console.WriteLine("Value produced is {0}", value),
                () => Console.WriteLine("Sequence completed normally"));

7、Merge 合并两个Observable

 IObservable<int> observable1 = new int[] { 1, 2, 3 }.ToObservable();
            IObservable<int> observable2 = new int[] { 5, 3, 8, 4 }.ToObservable();
            observable1.Merge(observable2).Subscribe(x=>Console.WriteLine(x));

8、CombineLatest 最近输入的两个数字相比较

 IObservable<int> observable1 = new int[] { 1, 2, 3 }.ToObservable();
            IObservable<int> observable2 = new int[] { 5, 3, 8, 4 }.ToObservable();
            var combineLatest = observable1.CombineLatest(observable2, (x1, x2) => x1 + x2).Subscribe(x=>Console.WriteLine(x));

A和B的序列，任何一边在引发变化时都会取出两边最新的值输出。

9、Publish 共享订阅事件

 var unshared = Observable.Range(1, 4);

            // Each subscription starts a new sequence
            unshared.Subscribe(i => Console.WriteLine("Unshared Subscription #1: " + i));
            unshared.Subscribe(i => Console.WriteLine("Unshared Subscription #2: " + i));

            Console.WriteLine();

            // By using publish the subscriptions are shared, but the sequence doesn't start until Connect() is called.
            var shared = unshared.Publish();
            shared.Subscribe(i => Console.WriteLine("Shared Subscription #1: " + i));
            shared.Subscribe(i => Console.WriteLine("Shared Subscription #2: " + i));
            shared.Connect();

10、Interval 订阅事件的时间间隔

 var observable = Observable.Interval(TimeSpan.FromMilliseconds(750)).TimeInterval();
            observable.Subscribe(x=>Console.WriteLine(x));

Timestamp 可以输出精确到秒后面7位数。

   var observable = Observable.Interval(TimeSpan.FromMilliseconds(750)).Timestamp();
            observable.Subscribe(x=>Console.WriteLine(x));

11、Group 分组

 var timeToStop = new ManualResetEvent(false);
            var keyPresses = KeyPresses().ToObservable();
            var groupedKeyPresses =
                from k in keyPresses
                group k by k.Key into keyPressGroup
                select keyPressGroup;
            Console.WriteLine("Press Enter to stop.  Now bang that keyboard!");
            groupedKeyPresses.Subscribe(keyPressGroup =>
            {
                int numberPresses = 0;
                keyPressGroup.Subscribe(keyPress =>
                {
                    Console.WriteLine(
                        "You pressed the {0} key {1} time(s)!",
                        keyPress.Key,
                        ++numberPresses);
                },
                () => timeToStop.Set());
            });
            timeToStop.WaitOne();

 static IEnumerable<ConsoleKeyInfo> KeyPresses()
        {
            for (; ; )
            {
                var currentKey = Console.ReadKey(true);

                if (currentKey.Key == ConsoleKey.Enter)
                    yield break;
                else
                    yield return currentKey;
            }
        }