Check if all items are same in a List in C#

This post will discuss how to check if all items are the same in a non-empty list in C#.

1. Using `Enumerable.Distinct` Method

A simple solution to check if all list items have the same value is to get the distinct elements count in the list using LINQ’s Enumerable.Distinct method. If all elements in the list are the same, then the distinct count would be 1. This is demonstrated below:

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> nums = new List<int>() { 1, 1, 1, 1, 1 };

bool isAllEqual = nums.Distinct().Count() == 1;

Console.WriteLine(isAllEqual); // True

}

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You can also skip the first element after getting the distinct elements from a sequence and check if there are any elements left, as the following example illustrates.

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> nums = new List<int>() { 1, 1, 1, 1, 1 };

bool isAllEqual = nums.Count > 0 && !nums.Distinct().Skip(1).Any();

Console.WriteLine(isAllEqual); // True

}

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2. Using `Enumerable.Any` Method

Another option to check if all list elements are identical is to compare each element of the list with its first element. This can be easily done using LINQ’s Enumerable.Any() method that returns true if and only if any element of a sequence satisfy a condition.

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> nums = new List<int>() { 1, 1, 1, 1, 1 };

bool isAllEqual = nums.Count > 0 && !nums.Any(x => x != nums.First());

Console.WriteLine(isAllEqual); // True

}

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Alternatively, you can use the Enumerable.All method that returns true if all elements of a sequence match the conditions defined by the supplied predicate, false otherwise.

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> nums = new List<int>() { 1, 1, 1, 1, 1 };

bool isAllEqual = nums.Count > 0 && nums.All(x => x == nums.First());

Console.WriteLine(isAllEqual); // True

}

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3. Using `List<T>.TrueForAll` Method

If you don’t prefer LINQ or do not use .NET 3.5 or above, you can use the List<T>.TrueForAll method that returns true if every element in the list satisfies the supplied predicate. Here’s an example of its usage:

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> nums = new List<int>() { 1, 1, 1, 1, 1 };

bool isAllEqual = nums.TrueForAll(x => x.Equals(nums.First()));

Console.WriteLine(isAllEqual); // True

}

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That’s all about checking if all items are the same in a List in C#.

Check if all items are same in a List in C#

1. Using Enumerable.Distinct Method

2. Using Enumerable.Any Method

3. Using List<T>.TrueForAll Method

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1. Using `Enumerable.Distinct` Method

2. Using `Enumerable.Any` Method

3. Using `List<T>.TrueForAll` Method