Honestly the fastest way to learn these lambda expressions is just to do katas the way you know how to do and then compare your solution. When I learned C# that's just what I did. :)

Do not think "I would have never come up with this simple solution", but rather "Oh so that's also a way to do it".

Keep on keeping on!

Ahh i came up with a very very simple way to cheat... oh well..
However looking at the other answers makes me realise that there is something other then a property that one can make public in an object..

According to my googlefoo (https://www.lucidchart.com/pages/flowcharts/star-trek) we have to cheat to win. However the warbird class is a completely empty object type. No Properties or Methods one could inject code into. I must be missing something :(

The C# test cases (example and hidden ones) are wrong.
E.g. for the randomized "110 021 32667" it should return valid, but the test case expects invalid (check here: https://planetcalc.com/2464/)

Same for those example test cases...

The test cases also use the wrong C# order of parameters for AreEqual. And there are two that are exactly the same just pasted after one another..

This (or at least the C# version of it) is a very low effort kata :/ Whoever translated it: shame on you

What language? For C# the expected and actual values are the wrong way around.

The parameters of the c# tests are the wrong way around. The expected value should be the first paramter, the actual one to test should come second.

The test case for 289 is wrong (c#).
When deleting every 17th number 289 will get deleted, too. (since 17*17 is 289). Thus 289 is NOT a survivor.
Or am I missing something?