Single question mark (?) means null check.
Basically, if Console.ReadLine is null, the other part will not be implemented.
In other words, Console.ReadLine()?.ToLower()
is equal to this
var dummy = Console.ReadLine();
if(dummy !== null)
{
dummy.ToLower()....
}
0
solved why you put a ? in Console.ReadLine() and ToLower() [duplicate]