如何在某种类型的数组中找到所有元素？

Question

I've never worked with predicates before so I'm having a lot of trouble using Array.FindAll

Basically I have an array of my own custom enum here public enum Colors { Empty, Blue, Red, Green, Purple, White, Orange };

My issue is I don't understand how to use FindAll to count the number of times a certain color occurs in the array. I was going to do something like this...

Colors matches[];
matches = Array.FindAll(myArray,/*I don't know what to put here*/);
int numOfMatches = matches.length;

What do I use as the second paramater to find a color like Blue for example?

Answer 1

You need to pass a predicate. In this case, you would check to see if the given color was equal to the one you are interested in:

var matches = Array.FindAll(myArray, c => c == someColor);

You could also use the Enumerable.Count method to find the number of matches (if you don't need to use them for anything else afterward):

var numOfMatches = myArray.Count(c => c == someColor);

Answer 2

You can use LINQ to do that:

int numOfBlue = matches.Count(m => m == Colors.Blue);

It will return just a number, instead of returning new array with matching elements.