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C# ToCharArray: Convert String to ArrayCall the ToCharArray method to convert a string to a char array.
ToCharArray. This method converts strings to character arrays. It is called on a string and returns a new char array. The original string is left unchanged.
Method usage. We can manipulate a char array in-place, which we cannot do with a string. This makes many performance optimizations possible.
Char Array
Char
An 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
using System; class Program { static void Main() { // 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; class Program { const int _max = 2000000; static void Main() { // 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).
Uppercase First Letter
Reverse String
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, String
Internals. ToCharArray uses unsafe code that manipulates pointers, along with the private wstrcpyPtrAligned method in the base class library.
And Optimized C++ code is normally faster than doing the same thing in managed code, which has to check array bounds.
Note ToCharArray makes a complete pass over the string, so if you do not require that, filling character arrays manually may be faster.
A summary. 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.
Review, performance. We looked at practical uses of ToCharArray and its internals in the base class library. It has advanced optimizations.
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