What is the most concise way to emit consecutive values every interval starting immediately using system.reactive?

Asked Jan 22 '19 at 16:01

Active Jan 22 '19 at 17:26

Viewed 27 times

Consider the following code in Linqpad:

DateTime.Now.Dump();
Observable
    .Interval(TimeSpan.FromSeconds(3))
    //.Select(n => n + 1)
    //.StartWith(0)
    .Do(n => $"{DateTime.Now} {n}".Dump())
    .Wait();

It outputs:

1/22/2019 12:23:57 PM
1/22/2019 12:24:00 PM 0
1/22/2019 12:24:03 PM 1

Notice that the first element is observed 3 seconds later. I want it to be right away, which is on subscription, I suppose. My solution is:

DateTime.Now.Dump();
Observable
    .Interval(TimeSpan.FromSeconds(3))
    .Select(n => n + 1)
    .StartWith(0)
    .Do(n => $"{DateTime.Now} {n}".Dump())
    .Wait();

Which produces:

1/22/2019 12:26:10 PM
1/22/2019 12:26:10 PM 0
1/22/2019 12:26:13 PM 1
1/22/2019 12:26:16 PM 2

Note the first element is observed right away.

I was wondering if there is a more concise way to achieve this.

edited Jan 22 '19 at 17:26

asked Jan 22 '19 at 16:01

mark

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what do you mean by immedietally? Upon creation or subscription? – Krzysztof Skowronek Jan 22 '19 at 16:32
Hmm. Subscription I guess. – mark Jan 22 '19 at 17:19
Why is it a duplicate? I do not need a hot observable. Let me edit the post. – mark Jan 22 '19 at 17:20
then use `Observable.Timer(TimeSpan.FromMilliseconds(0), TimeSpan.FromMilliseconds(100))` – Krzysztof Skowronek Jan 22 '19 at 17:29
https://stackoverflow.com/questions/44165893/how-do-i-make-an-observable-interval-start-immediately-without-a-delay – Krzysztof Skowronek Jan 22 '19 at 17:29
Now I can see it is a duplicate. Thank you. – mark Jan 22 '19 at 17:32

What is the most concise way to emit consecutive values every interval starting immediately using system.reactive?

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