Question

Assuming I have the following string array:

string[] str = new string[] {"max", "min", "avg", "max", "avg", "min"}

Is it possbile to use LINQ to get a list of indexes that match one string?

As an example, I would like to search for the string “avg” and get a list containing

2, 4

meaning that “avg” can be found at str[2] and str[4].

Answer 1

.Select has a seldom-used overload that produces an index. You can use it like this:

str.Select((s, i) => new {i, s})
    .Where(t => t.s == "avg")
    .Select(t => t.i)
    .ToList()

The result will be a list containing 2 and 4.

Documentation here