How to check if two Strings are anagrams of each other using C#?

An anagram is a word or phrase formed by rearranging the letters of another word or phrase, using all the original letters exactly once. For example, "silent" and "listen" are anagrams because they contain the same letters in different arrangements.

In C#, there are several approaches to check if two strings are anagrams. The most common method is to sort the characters of both strings and compare them for equality.

Using Array.Sort() Method

The simplest approach is to convert both strings to character arrays, sort them, and then compare the sorted arrays −

Example

using System;

public class Demo {
   public static void Main() {
      string str1 = "silent";
      string str2 = "listen";
      
      char[] ch1 = str1.ToLower().ToCharArray();
      char[] ch2 = str2.ToLower().ToCharArray();
      
      Array.Sort(ch1);
      Array.Sort(ch2);
      
      string val1 = new string(ch1);
      string val2 = new string(ch2);

      if (val1 == val2) {
         Console.WriteLine("Both strings are anagrams");
      } else {
         Console.WriteLine("Both strings are not anagrams");
      }
   }
}

The output of the above code is −

Both strings are anagrams

Using Character Frequency Count

An alternative approach counts the frequency of each character in both strings. If the frequencies match, the strings are anagrams −

Example

using System;
using System.Collections.Generic;

public class AnagramChecker {
   public static bool AreAnagrams(string str1, string str2) {
      if (str1.Length != str2.Length) {
         return false;
      }
      
      Dictionary<char, int> charCount = new Dictionary<char, int>();
      
      // Count characters in first string
      foreach (char c in str1.ToLower()) {
         if (charCount.ContainsKey(c)) {
            charCount[c]++;
         } else {
            charCount[c] = 1;
         }
      }
      
      // Subtract counts for second string
      foreach (char c in str2.ToLower()) {
         if (!charCount.ContainsKey(c)) {
            return false;
         }
         charCount[c]--;
         if (charCount[c] == 0) {
            charCount.Remove(c);
         }
      }
      
      return charCount.Count == 0;
   }
   
   public static void Main() {
      string str1 = "race";
      string str2 = "care";
      
      Console.WriteLine($"'{str1}' and '{str2}' are anagrams: {AreAnagrams(str1, str2)}");
      
      str1 = "hello";
      str2 = "world";
      Console.WriteLine($"'{str1}' and '{str2}' are anagrams: {AreAnagrams(str1, str2)}");
   }
}

The output of the above code is −

'race' and 'care' are anagrams: True
'hello' and 'world' are anagrams: False

Using LINQ

A concise approach using LINQ to order the characters and compare −

Example

using System;
using System.Linq;

public class LinqAnagram {
   public static bool CheckAnagram(string str1, string str2) {
      return str1.ToLower().OrderBy(c => c).SequenceEqual(
             str2.ToLower().OrderBy(c => c));
   }
   
   public static void Main() {
      string[] pairs = { "listen", "silent", "elbow", "below", "study", "dusty" };
      
      for (int i = 0; i < pairs.Length; i += 2) {
         bool result = CheckAnagram(pairs[i], pairs[i + 1]);
         Console.WriteLine($"'{pairs[i]}' and '{pairs[i + 1]}': {result}");
      }
   }
}

The output of the above code is −

'listen' and 'silent': True
'elbow' and 'below': True
'study' and 'dusty': True

Comparison

Conclusion

Checking for anagrams in C# can be accomplished through sorting characters, counting character frequencies, or using LINQ. The character frequency method is most efficient with O(n) time complexity, while sorting approaches offer simplicity and readability for smaller datasets.