C# - Convert Char to String

Convert Char, String. A char can be converted to a one-character string. There are several ways to do this. The clearest method is the ToString method.

Notes, performance. Other implementations may have better performance. For example, we can use the string constructor. We test these methods.

ToString

First example. Here we have a character "x" and we convert it into a string with 2 different method calls. We use ToString, and the string constructor.

using System;

char value = 'x';

// Perform conversions.
string result = value.ToString();
Console.WriteLine("RESULT  LENGTH: {0}", result.Length);

string result2 = new string(value, 1);
Console.WriteLine("RESULT2 LENGTH: {0}", result2.Length);RESULT  LENGTH: 1
RESULT2 LENGTH: 1

Benchmark. In the Main entry point, both methods return an equivalent string from the char argument. Their results are equal. We test their runtime speed.

Version 1 The first method here, Method1, uses the string constructor to convert a char to a string.

Version 2 This version of the code calls the ToString virtual method on the char type.

Result Using the string constructor is a slightly faster approach. But other approaches, like lookup tables, are probably even better.

using System;
using System.Diagnostics;

class Program
{
    static string Method1(char value)
    {
        return new string(value, 1);
    }

    static string Method2(char value)
    {
        return value.ToString();
    }

    const int _max = 100000000;
    static void Main()
    {
        Console.WriteLine(Method1('c'));
        Console.WriteLine(Method2('c'));

        var s1 = Stopwatch.StartNew();
        // Version 1: use string constructor.
        for (int i = 0; i < _max; i++)
        {
            Method1('c');
        }
        s1.Stop();
        // Version 2: use ToString.
        var s2 = Stopwatch.StartNew();
        for (int i = 0; i < _max; i++)
        {
            Method2('c');
        }
        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"));
    }
}c
c
10.37 ns
10.48 ns

Timing results. On my system, the results consistently indicated that the string constructor was slightly faster. And this held true regardless of what order the methods were tested.

Note There is probably somewhat less overhead involved in calling the string constructor.

String Constructor

Lookup tables. We could implement a lookup table to get cached 1-char strings. The char could be used as an index into a precomputed array of strings.

And This would change a string allocation into an array element load. This improves performance.

ROT13

A summary. It is simplest to just use the ToString method call. We can sometimes use Substring to take a one-character string from an input string, avoiding the char type.

String Substring