Uppercase first letter

Strings sometimes have lowercase first letters. Uppercasing the first letter is often necessary. The result string has its first letter uppercased.

Strings with multiple words can be changed to title case. We can capitalize "Multiple Words." When we need to handle words, we have more complex logic.

First example

This method returns correctly uppercased strings. We provide an example of a static method that uppercases the first letter.

using System;

class Program
{
    static void Main()
    {
        Console.WriteLine(UppercaseFirst("houston"));
        Console.WriteLine(UppercaseFirst("dallas"));
        Console.WriteLine(UppercaseFirst("austin"));
    }

    static string UppercaseFirst(string s)
    {
        // Check for empty string.
        if (string.IsNullOrEmpty(s))
        {
            return string.Empty;
        }
        // Return char and concat substring.
        return char.ToUpper(s[0]) + s.Substring(1);
    }
}
Houston
Dallas
Austin

Example 2

Next, we look at a method that uses the ToCharArray method instead. We investigate ToCharArray and its performance impact on this kind of character-based method.

using System;

class Program
{
    static void Main()
    {
        Console.WriteLine(UppercaseFirst("quebec"));
    }

    static string UppercaseFirst(string s)
    {
        if (string.IsNullOrEmpty(s))
        {
            return string.Empty;
        }
        char[] a = s.ToCharArray();
        a[0] = char.ToUpper(a[0]);
        return new string(a);
    }
}
Quebec

Uppercase words

This program defines a method named UppercaseWords that is equivalent to the ucwords function in PHP. UppercaseWords converts the string to a character array buffer.

using System;

class Program
{
    static string UppercaseWords(string value)
    {
        char[] array = value.ToCharArray();
        // Handle the first letter in the string.
        if (array.Length >= 1)
        {
            if (char.IsLower(array[0]))
            {
                array[0] = char.ToUpper(array[0]);
            }
        }
        // Scan through the letters, checking for spaces.
        // ... Uppercase the lowercase letters following spaces.
        for (int i = 1; i < array.Length; i++)
        {
            if (array[i - 1] == ' ')
            {
                if (char.IsLower(array[i]))
                {
                    array[i] = char.ToUpper(array[i]);
                }
            }
        }
        return new string(array);
    }

    static void Main()
    {
        // Uppercase words in these strings.
        const string value1 = "something in the way";
        const string value2 = "dot net PERLS";
        const string value3 = "String_two;three";
        const string value4 = " sam";
        // ... Compute the uppercase strings.
        Console.WriteLine(UppercaseWords(value1));
        Console.WriteLine(UppercaseWords(value2));
        Console.WriteLine(UppercaseWords(value3));
        Console.WriteLine(UppercaseWords(value4));
    }
}
Something In The Way
Dot Net PERLS
String_two;three
 Sam

Benchmark

What is the fastest way to uppercase the first letter in a string? We compare the 2 versions of UppercaseFirst in a benchmark program.

using System;
using System.Diagnostics;

class Program
{
    static string UppercaseFirst(string s)
    {
        if (string.IsNullOrEmpty(s))
        {
            return string.Empty;
        }
        return char.ToUpper(s[0]) + s.Substring(1);
    }

    static string UppercaseFirst2(string s)
    {
        if (string.IsNullOrEmpty(s))
        {
            return string.Empty;
        }
        char[] a = s.ToCharArray();
        a[0] = char.ToUpper(a[0]);
        return new string(a);
    }

    const int _max = 1000000;
    static void Main()
    {
        var s1 = Stopwatch.StartNew();
        // Version 1: test first method.
        for (int i = 0; i < _max; i++)
        {
            if (UppercaseFirst("denver") != "Denver")
            {
                return;
            }
        }
        s1.Stop();
        var s2 = Stopwatch.StartNew();
        // Version 2: test second method.
        for (int i = 0; i < _max; i++)
        {
            if (UppercaseFirst2("denver") != "Denver")
            {
                return;
            }
        }
        s2.Stop();
        Console.WriteLine(((double)(s1.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns"));
        Console.WriteLine(((double)(s2.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns"));
    }
}
60.66 ns    UppercaseFirst
42.66 ns    UppercaseFirst2

Notes, performance

The UppercaseWords method could be implemented by first splitting on the sub-words. But this would result in more allocations.

ToTitleCase

We do not always need a custom method for uppercasing the first letter in each word in a string. We can use ToTitleCase method on the TextInfo type.

We looked at methods that uppercase the first character in strings. They are useful for data that may not be correctly formatted. Custom logic for certain names can be added.