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Character Occurrence in a String in C#

Suzan Kara

In this article, I will discuss how to count the number of occurrences of a character in a string in C# in different ways. This detailed article will cover the following topics,

  1. Introduction
  2. Different ways to count character occurrence in a string in C#
  3. Conclusion

Character Occurrence in a String in C#’ is one of the most frequently asked questions in interviews. This tutorial will show you different ways to count the number of occurrences of a character in a string in C#.

Different ways to count character occurrence in a string in C#

Method. Using Loop to count character occurrence in a String in C#

In the following program, we take a string from the user, remove spaces from it, and then use a for loop to count the occurrence of each character in the string. Let’s see.

internal class UsingLoop
{
    static void Main(string[] args)
    {
        Console.Write("Enter the String: ");
        string str = Console.ReadLine();

        str = str.Replace(" ", string.Empty);   //Remove the empty spaces from the message

        while (str.Length > 0)
        {
            int count = 0;
            for (int i = 0; i < str.Length; i++)
            {
                if (str[0] == str[i])
                {
                    count++;
                }
            }
            Console.WriteLine($"Character '{str[0]}' appears {count} time(s) ");
            str = str.Replace(str[0].ToString(), string.Empty);
        }
        Console.ReadLine();
    }
}

Output

Method 2. Using a Dictionary to count the number of characters of a string in C#

In the following program, we take a string from the user, and then use a Dictionary to count the occurrence of each character in the string. Let’s see.

internal class UsingDictionary
{
    static void Main(string[] args)
    {
        Console.Write("Enter the string: ");
        string message = Console.ReadLine();

        message = message.ToLower();    // Optional: Convert the string to lowercase to ignore case sensitivity

        Dictionary<char, int> dict = new Dictionary<char, int>();

        foreach (char ch in message.Replace(" ", string.Empty))
        {
            if (dict.ContainsKey(ch))
            {
                dict[ch] = dict[ch] + 1;
            }
            else
            {
                dict.Add(ch, 1);
            }
        }
        foreach (var item in dict)
        {
            Console.WriteLine($"Character '{item.Key}' appears {item.Value} time(s)");
        }
        Console.ReadLine();
    }
}

Output

Method 3. Using Linq Group By to count the number of characters of a string in C#

In the following program, we take a string from the user, and then use the LINQ Group By method to count the occurrence of each character in the string. Let’s see.

internal class UsingLinqGroupBy
{
    static void Main(string[] args)
    {
        Console.Write("Enter the string: ");
        string str = Console.ReadLine();

        str = str.ToLower();    // Optional: Convert the string to lowercase to ignore case sensitivity

        Dictionary<char, int> dict = str.Replace(" ", string.Empty)
                                     .GroupBy(ch => ch)
                                     .ToDictionary(gb => gb.Key, gb => gb.Count());

        foreach (var item in dict.Keys)
        {
            Console.WriteLine($"Character '{item}' appears {dict[item]} time(s)");
        }
        Console.ReadLine();
    }
}

Output

Conclusion
In this article, we have discussed different ways to count the character occurrence of a string in C# with examples. I hope you enjoyed this blog. Follow C# Corner to learn more new and amazing things about C#.

Thanks for reading.

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