C# Capitalize First Letter

1. Use the ToUpper() Method to Capitalize the First Letter of a String in C#
2. Use the regex Expressions to Capitalize the First Letter of a String in C#
3. Use the ToCharArray() to Capitalize the First Letter of a String in C#

In this tutorial, we will look at multiple ways how to capitalize the first letter of a string in C#.

Use the ToUpper() Method to Capitalize the First Letter of a String in C#

using System;
class Program {
  static void Main() {
    string str = "delftstack";

    if (str.Length == 0) {
      Console.WriteLine("Empty String");
    } else if (str.Length == 1) {
      Console.WriteLine(char.ToUpper(str[0]));
    } else {
      Console.WriteLine(char.ToUpper(str[0]) + str.Substring(1));
    }
  }
}

In this approach, we capitalize the first letter of string using the ToUpper() method with corner cases like the string being empty or the string being length 1.

Use the regex Expressions to Capitalize the First Letter of a String in C#

using System;
using System.Text.RegularExpressions;

class Program {
  static public string UpperCaseFirstChar(string text) {
    return Regex.Replace(text, "^[a-z]", m => m.Value.ToUpper());
  }
  static void Main() {
    string str = "delftstack";
    Console.WriteLine(UpperCaseFirstChar(str));
  }
}

Output:

Delftstack

In the above method, we use the regex expression to select the desired character and then replacement with its capitalized form.

Use the ToCharArray() to Capitalize the First Letter of a String in C#

using System;

class Program {
  public static string UpperCaseFirstChar(string s) {
    if (string.IsNullOrEmpty(s)) {
      return string.Empty;
    }
    char[] a = s.ToCharArray();
    a[0] = char.ToUpper(a[0]);
    return new string(a);
  }
  public static void Main() {
    Console.WriteLine(UpperCaseFirstChar("delftstack"));
  }
}

Output:

Delftstack

In this approach, we capitalize the first letter of string by capturing it in a character array and then replacing the first character with its capital counterpart. Once the replacement is performed, we form a new string using the modified character array.