November 18

When I Get a New Job, I’m Updating My Licenses

If you’ve been paying attention to LinkedIn, you’ve probably noticed that I am looking for a new job. If you are hiring and you would like to talk, shoot me an email.

When I get this new job and I have some income, I’m going to update my licenses for the following Linqpad and NCrunch.

LINQPad

I love this app. I first used this back during my tenure at Logica when we were working with StreamInsight. It’s a good app to use to be able to quickly test out chunks of C#, VB.NET, and F# code. The app is extensible so you can download other drivers that let you hook up to other SQL/NoSQL databases. Really cool for learning/prototyping code. Check out the website for more information: https://www.linqpad.net.

NCrunch

NCrunch is an automated concurrent testing for Visual Studio. What that means in English is that you can configure it to run your unit tests as you are typing your code. You can configure it to run the unit tests that are impacted by the changes you make so you aren’t running the entire suite of unit tests. This is very handy, especially if you have good code coverage. It even collects code coverage numbers and performance metrics. More information can be found on the website: https://www.ncrunch.net.

Category: .NET, Reactive Extensions, Tools, unit testing | Comments Off on When I Get a New Job, I’m Updating My Licenses
August 1

How to Detect Concurrent Events Using LINQ and Reactive Extensions

Here’s the scenario…

I have 3 referees around a powerlifting platform. Each has a set of 4┬áswitches in their hand that is used to indicate if they thought a lift was good or not. One switch indicates the lift was good and the other 3 indicate the lift was no good and the general reason why. A referee’s light box displays the result by turning lights on and off. The individual lights should only turn on when all 3 referees have pushed their buttons. How do I determine when all 3 referees have pushed their buttons?

To get started, we need to create a simple event to indicate a referees decision.
public class RefereeDecisionEvent
{
public DateTimeOffset Timestamp { get; set; }
public DecisionCode Decision { get; set; }
}

The Decision property will hold a referee’s decision represented as a DecisionCode enumeration.

public enum DecisionCode
{
White = 0,
Red = 1,
Blue = 2,
Yellow = 4
}

White indicates the referee decided it was a good lift. Red, Blue, and Yellow represent potential reasons why the referee decided the lift was no good.

We’ll also need 3 event sources. Each event source represents a different referee; left, center, right. The actual implementation of the sources is outside the scope of this blog post. That said, I’ll just generate some events for each source at different intervals to give us some simple test data.

Step 1 is to join the left source’s events with the right source’s events. Since the left and right event sources create new events at different intervals, the events will most likely not occur at exactly the same time. We can fix this by increasing the duration of both sequences of events by 3 seconds. Now, we are joining the events from the left and the right sources when they occur within 3 seconds of each other.

var step1 = leftSource.Join(rightSource,
l => Observable.Interval(TimeSpan.FromSeconds(3)),
r => Observable.Interval(TimeSpan.FromSeconds(3)),
(l, r) => new {Left = l, Right = r});

Step 2 is to join the center source’s events with the now joined left and right side events. We’ll extend the durations of the events 3 seconds so that we can get a combined event that shows the left, center, and right events that all occurred withing 3 seconds of each other.

var step2 = centerSource.Join(step1,
l => Observable.Interval(TimeSpan.FromSeconds(3)),
r => Observable.Interval(TimeSpan.FromSeconds(3)),
(l, r) => new {r.Left, Center = l, r.Right});

In Step 3, we’ll project the results of step 2 into an event that is better laid out for our purposes. That Observable can then be subscribed to by an Observer that handles turning the lights on and off.

var step3 = from e in step2
select new
{
e.Left,
e.Center,
e.Right,
Status = new[] {e.Left.Decision, e.Center.Decision, e.Right.Decision}.Count(x => x == DecisionCode.White) >= 2 ? "Good" : "Bad"
};

And that’s how it’s done.

Category: C#, Reactive Extensions | Comments Off on How to Detect Concurrent Events Using LINQ and Reactive Extensions