C# Cookbook

2.21. Improving String Comparison Performance

Problem

Your application consists of many strings that are compared frequently. You have been tasked with improving performance and making more efficient use of resources.

Solution

Use the intern pool to improve resource usage and, in turn, improve performance. The Intern and IsInterned instance methods of the string class allow you to use the intern pool. Use the following static methods to make use of the string intern pool:

using System;
using System.Text;

public class InternedStrCls
{
    public static void CreateInternedStr(char[] characters)
    {
        string NonInternedStr = new string(characters);
        String.Intern(NonInternedStr);
    }

    public static void CreateInternedStr(StringBuilder strBldr)
    {
        String.Intern(strBldr.ToString( ));
    }

    public static void CreateInternedStr(string str)
    {
        String.Intern(str);
    }

    public static void CreateInternedStr(string[] strArray)
    {
        foreach(string s in strArray)
        {
            String.Intern(s);
        }
    }
}

Discussion

The CLR automatically stores all string literals declared in an application in an area of memory called the intern pool. The intern pool contains a unique instance of each string literal found in your code, which allows for more efficient use of resources by not storing multiple copies of strings that contain the same string literal. Another benefit is speed. When two strings are compared using either the == operator or the Equals instance method of the string class, a test is done to determine whether each string ...