How to get index of element in array C# LINQ

For example, Find the index of an item in an array using LINQ

int[] numbers = { 10, 20, 30, 40, 50 };
int elementToFind = 40;

// linq select index of item in array
int index = numbers.Select((value, idx) => new { value, idx })
               .Where(x => x.value == elementToFind)
               .Select(x => x.idx)
               .FirstOrDefault();

Console.WriteLine(index); // Output 3

First, we will create an anonymous object containing both the value and its index using Select. Then, we will use Where to filter the collection and find the object that matches the desired value. The Select method will extract the index of the matched object. Finally, we use FirstOrDefault to get the first index found.