C# - String ToCharArray Example

ToCharArray. This C# method converts strings to character arrays. It is called on a string and returns a new char array. The original string is left unchanged.

It is possible to manipulate a char array in-place, which we cannot do with a string. This makes many performance optimizations possible.

char Array

char

Example. First we use ToCharArray() to get a character array from the contents of a string. The example uses an input string, and then assigns a char array to the result of ToCharArray.

Next It uses a for-loop to get each character in the array, finally writing it to the Console.

for

Console.WriteLine

using System;

// Input string.
string value = "abcd";

// Use ToCharArray to convert string to array.
char[] array = value.ToCharArray();

// Loop through array.
for (int i = 0; i < array.Length; i++)
{
    // Get character from array.
    char letter = array[i];
    // Display each letter.
    Console.Write("Letter: ");
    Console.WriteLine(letter);
}Letter: a
Letter: b
Letter: c
Letter: d

Benchmark, ToCharArray. Here we measure the performance of ToCharArray. We copy a string to a char array with 2 versions of C# code.

Version 1 This uses ToCharArray. We make sure the resulting string has a correct first character each time.

Version 2 We allocate a char array of the required length, and then copy each character in from the source string.

Result ToCharArray is faster on a 300-char string. But if we try a smaller string, ToCharArray may be slower—make sure to test.

using System;
using System.Diagnostics;

const int _max = 2000000;
// Create 500-char string.
string text = new string('P', 500);
// Version 1: use ToCharArray.
var s1 = Stopwatch.StartNew();
for (int i = 0; i < _max; i++)
{
    char[] result = text.ToCharArray();
    if (result[0] != 'P')
    {
        return;
    }
}
s1.Stop();
// Version 2: copy chars from string with loop.
var s2 = Stopwatch.StartNew();
for (int i = 0; i < _max; i++)
{
    char[] result = new char[text.Length];
    for (int v = 0; v < text.Length; v++)
    {
        result[v] = text[v];
    }
    if (result[0] != 'P')
    {
        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")); 68.30 ns    ToCharArray
323.36 ns    new char[], for loop

Uses. With ToCharArray, the char array you receive is mutable. You can change characters. The method is ideal for transforming chars (like in ROT13, or uppercasing the first letter).

String Uppercase First Letter

String Reverse

ROT13

Also Often you will need to change your char array back to a string. You can use the new string constructor for this.

String Constructor

Convert Char Array

ToCharArray is often useful: it returns a character array filled with the string's characters. We can modify this array in-place—this improves the performance of code.