C# 截取两个字符串中间的子字符串

/// <summary>
/// 截取中间字符
/// </summary>
/// <param name="text">全字符串</param>
/// <param name="start">开始字符串 </param>
/// <param name="end">结束字符串 </param>
/// <returns></returns>
public static string Substring(string text,string start,string end)
{
    Regex regex = new Regex("(?<=(" + start + "))[.\\s\\S]*?(?=(" + end + "))", RegexOptions.Multiline | RegexOptions.Singleline);
    return regex.Match(text).Value;
}

/// <summary>
        /// 包含多个，截取中间字符，返回数组
        /// </summary>
        /// <param name="text">全字符串</param>
        /// <param name="start">开始字符串 </param>
        /// <param name="end">结束字符串 </param>
        /// <returns></returns>
        public string[] GetAllMatchedItems(string text, string start, string end)
        {
            Regex reg = new Regex("(?<=(" + start + "))[.\\s\\S]*?(?=(" + end + "))", RegexOptions.Multiline | RegexOptions.Singleline);
            int count = reg.Matches(text).Count;
            string[] Items = new string[count];
            for (int i = 0; i < count; i++) {
                Items[i] = reg.Matches(text)[i].Value;
            }
            return Items;
        }

 /// <summary>
        /// 获取双引号间的字符串
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        internal string GetBetweenDoubleQuoteString(string str) {
            Regex regex = new Regex("\"[^\"]*\"");
            return regex.Match(str).Value.Replace("\"", "");
        }