c# 用正則表達式獲取開始和結束字符串中間的值

/// <summary>
/// 獲得字符串中開始和結束字符串中間得值
/// </summary>
/// <param name="str">字符串</param>
/// <param name="s">開始</param>
/// <param name="e">結束</param>
/// <returns></returns>
public static string GetValue(string str, string s, string e)
{
Regex rg = new Regex("(?<=(" + s + "))[.\\s\\S]*?(?=(" + e + "))", RegexOptions.Multiline | RegexOptions.Singleline);
return rg.Match(str).Value;
}