dont understand (linq)

Question

for what is the new keyword and these things = []
///
return string.Concat(str.SelectMany(c=>new []{c,c}));
///
https://edabit.com/challenge/fKZHLzmR8anBrxgNt

Answer 1

Michael This might be a little late... but here is a code explaining this for you.
https://code.sololearn.com/co4NH3ER25wF/?ref=app
Basically this part of the code:
new[] {c, c}
Creates a new char array containing two copies of the same character.
See my code to see more details.

Answer 2

Nice