Print first letter of each word in a string using C# regex

In C#, you can use regular expressions to extract the first letter of each word from a string. This technique uses the Regex.Matches() method with a specific pattern to identify word boundaries and capture the initial characters.

Syntax

The regular expression pattern to match the first letter of each word is −

@"\b[a-zA-Z]"

Where −

• \b − represents a word boundary
• [a-zA-Z] − matches any single letter (uppercase or lowercase)

The Regex.Matches() method syntax −

MatchCollection matches = Regex.Matches(inputString, pattern);

How It Works

The word boundary \b ensures we only match letters that start a new word, not letters in the middle of words. This makes the pattern highly effective for extracting word initials.

Example

using System;
using System.Text.RegularExpressions;

namespace RegExApplication {
   public class Program {
      private static void showMatch(string text, string expr) {
         Console.WriteLine("The Expression: " + expr);
         MatchCollection mc = Regex.Matches(text, expr);
         foreach (Match m in mc) {
            Console.WriteLine(m);
         }
      }
      
      public static void Main(string[] args) {
         string str = "The Shape of Water got an Oscar Award!";
         Console.WriteLine("Display first letter of each word!");
         showMatch(str, @"\b[a-zA-Z]");
      }
   }
}

The output of the above code is −

Display first letter of each word!
The Expression: \b[a-zA-Z]
T
S
o
W
g
a
O
A

Alternative Approach Using String Join

You can also combine all first letters into a single string −

using System;
using System.Text.RegularExpressions;
using System.Linq;

class Program {
   public static void Main() {
      string str = "The Shape of Water got an Oscar Award!";
      Console.WriteLine("Original string: " + str);
      
      MatchCollection matches = Regex.Matches(str, @"\b[a-zA-Z]");
      string firstLetters = string.Join("", matches.Cast<Match>().Select(m => m.Value));
      
      Console.WriteLine("First letters: " + firstLetters);
   }
}

The output of the above code is −

Original string: The Shape of Water got an Oscar Award!
First letters: TSoWgaOA

Common Use Cases

• Creating acronyms − Extract initials to form abbreviations

• Text processing − Analyze document structure by examining word patterns

• Data validation − Check if text follows specific formatting rules

• Search optimization − Create searchable indexes based on word initials

Conclusion

Using the regex pattern \b[a-zA-Z] with Regex.Matches() is an efficient way to extract the first letter of each word in a string. The word boundary \b ensures precise matching at the start of words, making this approach reliable for text processing tasks.