CharEnumerator

This C# type is used to loop over a string. The CharEnumerator is acquired through the GetEnumerator method on the string type.

Type info

CharEnumerator offers few advantages over other constructs. But it can be used when an interface (IEnumerator) is required by a method.

Example program

This program declares a string literal and then calls the GetEnumerator method. It shows the usage in C# of CharEnumerator.

using System;

class Program
{
    static void Main()
    {
        // Input string.
        string val = "dotnet";
        // Get enumerator.
        CharEnumerator e = val.GetEnumerator();
        // Use in loop.
        while (e.MoveNext())
        {
            char c = e.Current;
            Console.WriteLine(c);
        }
    }
}
d
o
t
n
e
t

Performance

You can loop through strings with foreach and for-loops. I wondered if the CharEnumerator version of the string loop had any advantage over these methods.

using System;
using System.Diagnostics;

class Program
{
    const int _max = 100000000;
    static void Main()
    {
        var s1 = Stopwatch.StartNew();
        // Version 1: use CharEnumerator.
        for (int i = 0; i < _max; i++)
        {
            Method1("test");
        }
        s1.Stop();
        var s2 = Stopwatch.StartNew();
        // Version 2: use foreach-loop.
        for (int i = 0; i < _max; i++)
        {
            Method2("test");
        }
        s2.Stop();
        Console.WriteLine(((double)(s1.Elapsed.TotalMilliseconds * 1000 * 1000) / _max).ToString("0.00 ns"));
        Console.WriteLine(((double)(s2.Elapsed.TotalMilliseconds * 1000 * 1000) / _max).ToString("0.00 ns"));
    }

    static int Method1(string val)
    {
        int res = 0;
        CharEnumerator c = val.GetEnumerator();
        while (c.MoveNext())
        {
            res += (int)c.Current;
        }
        return res;
    }

    static int Method2(string val)
    {
        int res = 0;
        foreach (char c in val)
        {
            res += (int)c;
        }
        return res;
    }
}
33.33 ns    CharEnumerator
 4.79 ns    foreach

Discussion

Using CharEnumerator directly is not usually worthwhile. But if you have a reference of type IEnumerator, you can use CharEnumerator through those types.

Summary

The CharEnumerator type presents an implementation of an enumerator for the string type. To get a CharEnumerator, call GetEnumerator on a string instance.