Does LINQ work on Index?

arrays, c#, linq

Solution

This is what I ended up doing in LINQ (update included):

myarr.Select((b, i) => b == 4 ? i : -1)
    .Where(i => i != -1)
    .ToList().ForEach(i => val[i]++);

Your non-LINQ version is obviously much more succinct and readable, so I think you should use that.

Problem

Lets say i have an array ``` byte[] myarr = {1,4,3,4,1,2,1,2,4,3,1,4,2}; ``` myarr will be of length 13 (0-12 Index) which will also be the length of int[] val. ``` int[] val = new int[13]; ``` I want to check index of myarr where its value is 4 i.e. 1,3,8,11. Then i want ``` val[1]++; val[3]++; val[8]++; val[11]++; ``` One way of doing this is using for loop ``` for(int i=0; i<myarr.length; i++) { if(myarr[i] == 4) val[i]++; } ``` We can use Array.indexof but it returns the first index of that value meaning that value has to be unique and my myarr has lots of same values. Can this be done using linq?

Original source