I got some errors

Question

this is code to caliculate permutation, combination and factorial.
only caliculation of factorial puts out errors.
how can i solve this?

https://code.sololearn.com/c6o5z9mFE829/?ref=app

Answer 1

You have an error in line 40. If you want to use 'Select' method you must provide appropriate selector function (in your case it will be a method which takes string as an argument and returns int). You can write this as lambda expression: s => int.Parse(s).
Another problem is that after splitting a string with '!' at the end of the string you will get an array with 2 elements (the last element is an empty string) so you should do some additional check to avoid parsing errors (for example if string is not empty).

line 40:
static int[] nums = strnums.Where(s => s != string.Empty).Select(s => int.Parse(s)).ToArray();

Answer 2

code worked correctly.
actually i used Select method by c&p. but thank to your answer i understood system of the method.
thank you so much!