Check if two Lists are equal in C#

This post will discuss how to check if two Lists are equal in C#. Two lists are considered equal if are structurally equal. i.e. they have the same values, in the same order.

1. Using `Enumerable.SequenceEqual` Method

The standard solution to check for structural equality in C# is using the Enumerable.SequenceEqual method from LINQ. It compares the corresponding elements of both sequences with the custom or default equality comparer. Here’s an example of its usage:

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<string> first = new List<string>() { "A", "B", "C" };

List<string> second = new List<string>() { "A", "B", "C" };

bool isEqual = first.SequenceEqual(second);

Console.WriteLine(isEqual); // True

}

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This method requires .NET framework >= 3.5. Note that the == operator or Enumerable.Equals method checks for reference equality in C#. For example,

using System;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<string> first = new List<string>() { "A", "B", "C" };

List<string> second = new List<string>() { "A", "B", "C" };

bool isEqual = first.Equals(second);

Console.WriteLine(isEqual); // False

}

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2. Using Loop

You can even write your own custom routine for checking the equality of two lists. This can be implemented as follows in C# using regular for loop.

using System;

using System.Collections.Generic;

public static class Extensions

{

public static bool isEqual<T>(this List<T> first, List<T> second)

{

if (first == null && second == null) {

return true;

}

if (first == null || second == null || first.Count != second.Count) {

return false;

}

for (var i = 0; i < first.Count; i++)

{

var comparer = EqualityComparer<T>.Default;

if (!comparer.Equals(first[i], second[i])) {

return false;

}

return true;

}

public class Example

{

public static void Main()

{

List<string> first = new List<string>() { "A", "B", "C" };

List<string> second = new List<string>() { "A", "B", "C" };

bool isEqual = first.isEqual(second);;

Console.WriteLine(isEqual); // True

}

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3. Using `String.Join` Method

Finally, you can just compare the string representation of both lists with the == operator. The following solution uses the String.Join method to get the string representation of the specified list.

using System;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<string> first = new List<string>() { "A", "B", "C" };

List<string> second = new List<string>() { "A", "B", "C" };

bool isEqual = String.Join(",", first) == String.Join(",", second);

Console.WriteLine(isEqual); // True

}

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That’s all about checking if two Lists are equal in C#.

Check if two Lists are equal in C#

1. Using Enumerable.SequenceEqual Method

2. Using Loop

3. Using String.Join Method

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1. Using `Enumerable.SequenceEqual` Method

3. Using `String.Join` Method