Find current index in a foreach loop in C#

This post will discuss how to find the index of the current iteration in a foreach loop in C#.

The LINQ’s Select() method projects each element of a sequence into a new form by incorporating the element’s index. The first argument to selector represents the element to process, and the second argument represents the 0-based index of that element in the source sequence.

The following code example demonstrates using the Select() method to find each element’s index.

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> nums = new List<int>() { 3, 2, 5, 6, 4, 8 };

foreach (var item in nums.Select((value, index) => new { value, index })) {

Console.WriteLine("Element {1} present at index {0}", item.index, item.value);

}

Output:

Element 3 present at index 0

Element 2 present at index 1

Element 5 present at index 2

Element 6 present at index 3

Element 4 present at index 4

Element 8 present at index 5

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Alternatively, we can avoid heap allocations using the following alternative syntax using ValueTuple starting with C#7:

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> nums = new List<int>() { 3, 2, 5, 6, 4, 8, 7 };

foreach (var item in nums.Select((value, index) => (value, index))) {

Console.WriteLine("Element {1} present at index {0}", item.index, item.value);

}

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The following example uses type inference when deconstructing the list of 2-tuples returned by the Select() method. Now we can directly access the index and the value fields inside the loop.

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> nums = new List<int>() { 3, 2, 5, 6, 4, 8, 7 };

foreach (var (value, index) in nums.Select((value, index) => (value, index))) {

Console.WriteLine("Element {1} present at index {0}", index, value);

}

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That’s all about finding the current index in a foreach loop in C#.

Find current index in a foreach loop in C#

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