C#中查询字符串中是否包含指定字符/串，使用IndexOf还是Contains?

C#中查询字符串中是否包含指定字符/串，使用IndexOf还是Contains?这是一个很常见的命题，以前也没有注意，今天QQ群里有人提起，于是就做了下试验，代码如下：

using System;
using System.Diagnostics;

namespace ConsoleApplication1
{
    class Program
    {
        private const int N = 10000000;
        private static Stopwatch watch = new Stopwatch();
        static void Main(string[] args)
        {

            string source = "abcdefghijklmnopqrstuvwxyz0123456789C#"
                          + "中查询字符串中是否包含指定字符/串，使用IndexOf还是Contains?.uonun";
            string target = "a";
            Console.WriteLine("目标为第一个字符时：");
            TestContains(source, target);
            TestIndexOf(source, target);
            Console.WriteLine();

            Console.WriteLine("目标为中部某个字符时：");
            target = "中";
            TestContains(source, target);
            TestIndexOf(source, target);
            Console.WriteLine();

            Console.WriteLine("目标为最后一个字符时：");
            target = "u";
            TestContains(source, target);
            TestIndexOf(source, target);

            Console.WriteLine("执行完毕，按任意键退出...");
            Console.ReadKey();

        }
        private static void TestIndexOf(string source, string target)
        {
            watch.Reset();
            watch.Start();
            for (int i = 0;i < N;i++)
            {
                source.IndexOf(target);
            }
            watch.Stop();
            Console.WriteLine("IndexOf: " + watch.ElapsedMilliseconds.ToString() + "ms");
            return;
        }

        private static void TestContains(string source, string target)
        {
            watch.Reset();
            watch.Start();
            for (int i = 0;i < N;i++)
            {
                source.Contains(target);
            }
            watch.Stop();
            Console.WriteLine("Contains: " + watch.ElapsedMilliseconds.ToString() + "ms");
            return;
        }
    }
}