get index of element in list c# code example

Example 1: c# get index of item in list

Array.IndexOf(arrName, searchingFor)

Example 2: c# list any retun indec

public class Item {
	public int Id { get; set; }
	public Item() {}
	public Item(int id) { Id = id; }
}
List<Item> idList = { new Item(1), new Item(2), new Item(3) };
Item[] idLArr = [ new Item(1), new Item(2), new Item(3) ];

Item newItem = new Item(1);

// Using a lambda expression we can do the following query
int index = idList.FindIndex(item => item.Id == newItem.Id);
int arrIndex = Array.IndexOf(idLArr, newItem.Id);

//Then use it like so:
if (index != -1)
{
	// The item exists at index 0!
}

Example 3: index of item in list C#

List<string> strings = new List<string>(){"bob","ate","an", "apple"};
strings.IndexOf("bob");
//returns 0 
strings.IndexOf("an");
//returns 2
strings.IndexOf("apple");
//returns 3
strings.IndexOf("banana");
//returns -1
//Because banana is not in the list, IndexOf() returns -1