Linq - 获取最后一个非零数组的索引

Question

Is there a Linq expression that returns the index of the last non-zero value in an array? I'm not interested in an extension, only a simple linq expression.

I'm imagining something like this pseudo code:

int index = {0, 2, 1}.LastOrDefaultAt(i => i > 0);

The returned value should be 2;

Answer 1

You can use the Array.FindLastIndex<T> method for this:

int index = Array.FindLastIndex(myIntArray, item => item > 0);

I notice that you mention "non-zero" rather than "greater than zero" in your question text. Should your predicate be: item => item != 0 ?

Answer 2

List<T>有一个名为FindLastIndex的扩展方法

var index = new int[] { 0, 2, 1}.ToList().FindLastIndex(x => x > 0);

Answer 3

class Program
{
    static void Main(string[] args)
    {
        int[] index = { 0, 2, 1 };

        var query = from p in index
                    where p != 0
                    orderby p descending
                    select p;

        Console.WriteLine(query.FirstOrDefault());
        Console.ReadKey();
    }
}

Output: 2. Could be written in method syntax if desired:

var index = new int[] { 0, 2, 1 }.Where(a => a != 0).OrderByDescending(a => a).FirstOrDefault();