C# CharEnumerator

Use the CharEnumerator type to loop over a string. Measure CharEnumerator performance.

CharEnumerator. This is used to loop over a string. We test the CharEnumerator type. The CharEnumerator is acquired through the GetEnumerator method on the string type. It offers few advantages over other constructs.Char

To start, this program declares a string literal and then calls the GetEnumerator method. We then use a while-loop to repeatedly call the MoveNext method, which returns a bool. The Current property returns the current character.String Literal

C# program that uses 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); } } } Output d o t n e t

Performance. You should be aware of the other ways you can loop through strings, including the foreach and for-loops. I wondered if the CharEnumerator version of the string loop had any advantage over these methods.Loop Over String Chars

Benchmark: This benchmark tests a loop over a short four-character string using the CharEnumerator-style code, and the foreach-style code.

Result: The CharEnumerator method of looping over all the characters in a string is much slower than the foreach method.

Drawback: There is a significant drawback to ever using the CharEnumerator in a loop on a string in the C# language.

C# program that benchmarks CharEnumerator using System; using System.Diagnostics; class Program { const int _max = 100000000; static void Main() { var s1 = Stopwatch.StartNew(); for (int i = 0; i < _max; i++) { Method1("test"); } s1.Stop(); var s2 = Stopwatch.StartNew(); 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")); Console.Read(); } 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; } } Output 33.33 ns CharEnumerator 4.79 ns foreach

Discussion. Using CharEnumerator directly (as shown) is not appropriate. But if you have code that requires a reference of type IEnumerator or IEnumerator<char>, you can use the CharEnumerator through those types.

Note: CharEnumerator implements those interfaces. But this is not something that will occur in many programs.

Summary. The CharEnumerator type presents an implementation of an enumerator for the string type. To get a CharEnumerator, call GetEnumerator on a string instance. The performance of CharEnumerator is much worse than looping.

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.Net

.NET Array Dictionary List String 2D Async DataTable Dates DateTime Enum File For Foreach Format IEnumerable If IndexOf Lambda LINQ Parse Path Process Property Regex Replace Sort Split Static StringBuilder Substring Switch Tuple

Java

Core Array ArrayList HashMap String 2D Cast Character Console Deque Duplicates File For Format HashSet If IndexOf Lambda Math ParseInt Process Random Regex Replace Sort Split StringBuilder Substring Switch Vector While

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C# CharEnumerator

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