正文
#方法一：使用string.Contains方法
string.Contains是大小写敏感的，如果要用该方法来判断一个string是否包含某个关键字keyword，需要把这个string和这个keyword都转成小写或大写再调用Contains方法；
string key = "bbb";
string temp = "aaaBBBcccDDD";
bool isContains= temp.ToLower().Contains(key.ToLower());//true
#方法二：使用sring.Index方法
使用string.Index方法，然后通过StringComparison.OrdinalIgnoreCase指定查找过程忽略大小写；
string key = "bbb";
string temp = "aaaBBBcccDDD";
bool isContains = temp.IndexOf(key,StringComparison.OrdinalIgnoreCase)>=0;//true
#那什么时候使用Contains方法，什么时候使用Index方法，哪个效率高？
1、测试代码：
注：此测试针对的是拥有大量英文的情况下，并且指定的字符串为英文
每个方法测试1千万次，输出所用时间；
class Program
{
private const int N = 10000000;
private static Stopwatch watch = new Stopwatch();
static void Main(string[] args)
{
string source = "aaabbbcccdddeeefffggghhhiiijjjkkklllmmmnnnooopppqqq";
string target = "AAA";
Console.WriteLine("目标在开头部分时：");
Console.WriteLine("不区分大小写：");
TestContains(source, target,true);
TestIndexOf(source, target,true);
Console.WriteLine("区分大小写：");
target = "aaa";
TestContains(source, target,false);
TestIndexOf(source, target,false);
Console.WriteLine();
Console.WriteLine("目标在中部时：");
Console.WriteLine("不区分大小写：");
target = "HHH";
TestContains(source, target, true);
TestIndexOf(source, target, true);
Console.WriteLine("区分大小写：");
target = "hhh";
TestContains(source, target, false);
TestIndexOf(source, target, false);
Console.WriteLine();
Console.WriteLine("目标在结尾时：");
Console.WriteLine("不区分大小写：");
target = "QQQ";
TestContains(source, target,true);
TestIndexOf(source, target,true);
Console.WriteLine("区分大小写：");
target = "qqq";
TestContains(source, target,false);
TestIndexOf(source, target,false);
Console.WriteLine("执行完毕，按任意键退出...");
Console.ReadKey();
}
private static void TestIndexOf(string source, string target,bool isIgnoreCase)
{
watch.Reset();
watch.Start();
for (int i = 0; i < N; i++)
{
if (isIgnoreCase)
source.IndexOf(target, StringComparison.OrdinalIgnoreCase);
else
source.IndexOf(target);
}
watch.Stop();
Console.WriteLine("IndexOf: " + watch.ElapsedMilliseconds.ToString() + "ms");
return;
}
private static void TestContains(string source, string target,bool isIgnoreCase)
{
watch.Reset();
watch.Start();
for (int i = 0; i < N; i++)
{
if (isIgnoreCase)
source.ToLower().Contains(target.ToLower());
else
source.Contains(target);
}
watch.Stop();
Console.WriteLine("Contains: " + watch.ElapsedMilliseconds.ToString() + "ms");
return;
}
}
