在字符串中查找子字符串以在搜索的句子之前找到部分

Question

在：

 string str = "On the screen the faint, old, robed figure of Mercer toiled upward, and all at once a rock sailed past him.";

搜索子字符串：

 string find = "figure of";

如果这样：

 string reg = string.Format("({0} +([\\w+]+))", find);
 var result = new Regex(reg).Match(str);

我可以得到部分跟随搜索的句子：

figure of Mercer

但是如何在搜索的句子之前找到短语的一部分：

 On the screen the faint, old, robed

并且只获取最近的单词：

 robed

Answer 1

IndexOf 将帮助找到Substing 的起始索引

string str = "On the screen the faint, old, robed figure of Mercer toiled upward, and all at once a rock sailed past him.";
string find = "figure of";

var index = str.IndexOf(find);

if (index >= 0)
{
    var result = str.Substring(0, index);
    Console.WriteLine(result);
}