Regular Expressions Presentation

I have uploaded my notes from my presentation on Regular Expressions.  Currently, I am flushing out my presentation notes into a more readable format in the readme file, but I have uploaded everything now in case you want to get the raw notes early.  They can be found at:



When was the last time you sat down and talked to your team about problems?  What was the last task or procedure you changed because it was a bad fit for the project?  The longer you wait, the worse it gets because the longer a team works together, the less likely someone is going to mention a difficulty or a frustration.  Once people get used a routine that is bearable, they will learn to live with it even though it’s uncomfortable, and it’s this situation which leads to frustration, turnover and burnout.

I am fortunate to have a team who is vocal and willing to discuss issues.  The team is relatively good working through development scenarios where issues might arise.  Code deployments are automated, database updates are tested multiple times in varying scenarios, and every time an issue occurs that a change in process could help, we look at implementing it.  For a long time, we were diligent at applying this test and fix approach to everything except ourselves, and that is when the unexpected happened.  My team member completely shocked me and let me know that our communication with him was poor and he didn’t feel included.  He works remotely most of the time, and for the most part he was the only one.  The rest of the team would have conversations in hallways, etc., and to us this was the course of a normal day.  His knowledge and insights were being excluded, simply because we were making decisions about things we didn’t feel warranted an official meeting.

This left us in an awkward position.  We either needed to end the possibility of working remotely, or we needed to rethink how we communicated on a daily basis.  Our problem was that most of us didn’t even know we had a problem, and that certainly meant we didn’t know how to fix it.  Most organizations handle problems like this by minimizing scenarios where they have issues.  We took the opposite approach and forced ourselves to confront it, understand it, and from this we created a new policy; all people must now work remote at least one day a week.  Why did we take this approach?  We understood that remote work is too important to give up. We also understood that unless we analyzed what was wrong it would never improve.  In the end, we would rather take time to fix a problem than keep suffering through it.  This approach to helped not only communication with but showed us other areas for improvement as well.


For us to solve the problem, we must first all understand what it is.  With all people working away from the office, we can all see what problems there are with communication.  Each person can now look at how the team functions and provide a unique perspective on how to make it better.   We found that not only our communication with people off site improved, but with people on site as well.  We are now much more diligent about communicating ideas and decisions with everyone and we are much more cognizant about recording information where it can be accessed anywhere at any time.


Despite any attempt at quiet working conditions, most offices are a chaotic place.  Programming requires concentration and several tasks are only easy to accomplish when someone can have several hours of uninterrupted work.  Common pieces of advice include, “put on headphones” or “book a meeting room and close the door.”  These are fine, but there is always the possibility people will cause interruption.  While at home, coworkers cannot do this allowing greater relaxation which leads to an easier ability to focus.  Now that each team member has at least one day where work can be uninterrupted, they commonly save long tasks for when not at the office.

Disaster Recovery

Being able to access key internal systems from home is not just for people who live too far away to be on location.  We depend on it in cases when people can’t drive to the office, or when emergencies arise when we don’t have time to make the commute.  During a crisis is not the time to find out your equipment doesn’t function.  With each member testing remote access on a weekly basis, we have a relativity high certainty that it will work when we need it to.   This is a tool used in emergencies just like redundant servers, or a secondary site.  You can always hope it works when necessary, but you won’t know until you try.


Trust is something which everyone wants to believe exists but is often in short supply.  Most places have the capability to allow people to work remotely, but leaders often joke about their employees watching television instead. (I actually interviewed at a company where the hiring manager threateningly said that he’ll know if people aren’t doing work while they are remote.)  Allowing employees to work at home when necessary shows a level of implicit trust.  It tells employees management has enough faith in their work ethic that if its only once in a while the project won’t suffer too much.  Forcing someone to work remotely changes the narrative.  It becomes a common occurrence, and shows everyone they are trusted enough to do what they need to do.  Trust among a team is key.  It allows people to be open about issues and ideas for improvement, and without it teams will fail to improve.

Quirks with Pattern Matching in C# 7

With C# 7, Microsoft added the concept of pattern matching by enhancing the switch statement. Compared to functional languages (both pure and impure), this seems to be somewhat lacking in a feature by feature comparison, however it is still nice in allowing a cleaner format of code. With this, there are some interesting quirks, that you should be aware of before using. Nothing they’ve added breaks existing rules of the language, and with a thorough understanding how the language behaves their choices make sense, but there are some gotchas that on the surface looks like they should function one way, but act in a completely different manner.

Consider the following example.


C# 7 now allows the use of a switch statement to determine the type of a variable. It as also expanded the use of is to include constants including null.

is can show if something is null : shows true

With these two understandings, which line executes in the following code?

Shows default code executed.

Based on the previous examples, its a reasonable conclusion that the one of the first two case statements would execute, but they don’t.

The is operator

The is operator was introduced in C# 1.0, and its use has been expanded, but none of the existing functionality has changed. Up until C# 7, is has been used to determine if an object is of a certain type like so.

This outputs exactly as expected. The console prints “True” (Replacing string with var works the exactly the same. Remember that the object is still typed. var only tells the compiler to figure out what type the variable should be instead of explicitly telling it.)

Is Operator String: True

What happens if the string is null? The compiler thinks its a string. It will prevent you from being able to pass it to methods requiring another reference type even though the value is explicitly null.

Type is null

The is operator is a run time check not a compile time one, and since it is null, the runtime doesn’t know what type it is. In this example, the compiler could give flags to the runtime saying what type it actually is even though it’s null, but this would be difficult if not impossible for all scenarios, so for consistency, it still returns false. Consistency is key.

Printing out True and False is nice, but it’s not really descriptive. What about adding text to describe what is being evaluated.

Is Type With Question, Question doesn't appear

Why didn’t the question appear? It has to do with operator precedence. The + has a higher operator precedence than is and is evaluated first. What is actually happening is:

This becomes clear if the clause is flipped, because the compiler doesn’t know how to evaluate string when using the + operator.

Flipping clauses throws error.

Adding parenthesis around the jennysNumber is string fixes the issue, because parenthesis have a higher operator precedence than the + operator.

output of is operator and + flipped with parenthesis (shows both question and value)

Pattern Matching with Switch Statements

Null and Dealing with Types

Null is an interesting case, because as shown during the runtime, it’s difficult to determine what type an object is.

Base Example

This code works exactly as how you think it should. Even though the type is string, the runtime can’t define it as such, and so it skips the first case, and reaches the second.

Adding a type object clause works exactly the same way

shows object case works same way

What about var. Case statements now support var as a proposed type in the statement.

If you mouse over either var or the variable name, the compiler will tell you what type it is.
show compiler knows what type it is.

Shows var case statement doesn't know type

It knows what the type is, but don’t let this fool you into thinking it works like the other typed statements though. The var statement doesn’t care that the runtime can’t determine the type. A case statement with the var type will always execute provided there is no condition forbidding null values when (o != null). Like before, it still can’t determine the type inside the case statement statement.

Why determine object type at compile time?

At any point in time (baring the use of dynamic), the compiler knows the immediate type of the variable. It could use this to directly point the correct case concerning the type. If that were true, it couldn’t handle the following scenario, or any concerning inheritance of child types.

shows is string

Personally, I would like to see either a warning or an error, that it’s not possible for type cases to determine if the variable is null case string s when (s is null), but as long as the code is tested and developers knows about this edge case, problems can be minimized.

All the examples can be found on github:


I have been fortunate enough to be allowed to speak at Indy.Code() which really means I’m grateful to get the chance to listen to all the other speakers. If you live anywhere around the Midwest, or can travel to Indianapolis, I highly recommend you come and watch the talks. It’s going to be an amazing event with some unbelievably great speakers. A fun time will be had by all. (Unless you hate fun, then you probably won’t like it so much. For everyone else, it’ll be pretty great!)

C# 7 Additions – Pattern Matching

C# 7 has started to introduce Pattern Matching. This is a concept found in functional programming, and although it isn’t fully implemented compared to F#, it is a step in that direction. Microsoft has announced they intend on expanding it in future releases.

Constant Patterns

The is keyword has been expanded to allow all constants on the right side of the operator instead of just a type. Previously, C#’s only valid syntax was similar to:

Now it is possible to compare a variable to anything which is a constant: null, a value, etc.

Behind the scenes, the is statement is converted to calling the Equals function in IL code. The following two functions produce roughly the same code (they call different overloads of the Equals function).



This can also be combined with other features allowing variable assignment through the is operator.

In Visual Studio Preview 4, the scoping rules surrounding variables assigned in this manner are more restrictive than in the final version. Right now, they can only be used within the scope of the conditional statement.

Switch Statements

The new pattern matching extensions have also extended and changed the use of case statements. Patterns can now be used in switch statements.

Like in previous versions, the default statement will always be evaluated last, but the location of the other case statements now matter.

In this example, case int n will never evaluate, because the statement above it will always be true. Fortunately, the C# compiler will evaluate this, determine that it can’t be reached and raise a compiler error.

The variables declared in patterns behave differently than others. Each variable in a pattern can have the same name without running into a collision with other statements. Just as before, in order to declare a variable of the same name inside the case statement, you must still explicitly enforce scope by adding braces ({}).

Pattern matching has a ways to go when compared to its functional language equivalent, but it is still a nice addition and will become more complete as the language evolves.

C# 7 Additions – Literals

A small, but nice chance in C# 7 is increased flexibility in literals. Previously, large numeric constants had no separator, and it was difficult to easily read a large number. For example, if you needed a constant for the number of stars in the observable universe (1,000,000,000,000,000,000,000), you’d have to do the following:

If you hadn’t caught the error, the constant is too short, and it’s difficult to tell looking at the numbers without a separator. In C# 7, it’s now possible to use the underscore (_) in between the numbers. So the previous example now becomes much easier to read, and it is easily recognizable the number is off.

The new version adds binary constants too. Instead of writing a constant in hex, or decimal, a constant can now be written like so: