c#中如何获取指定字符前的字符串

string[] arry = ComBoBox.Text.Trim().split('|');
string 字符串 = arry[0];

        //调用
       MethodsCommon.TrimStr(",1234",",");
 
        /// <summary>
        /// 去除字符串前后逗号
        /// 如：1,2,5, 变成 1,2,5
        ///,,,1,2,5, 变成 1,2,5
        ///,,,,,,, 变成""
        /// </summary>
        /// <param name="str">字符串</param>
        /// <param name="symbol">要去除的符号</param>
        /// <returns></returns>
public static string TrimStr(string str,string symbol)
        {
           if (str == null || str == string.Empty)
            {
                return "";
            }
            int len = str.Length;
            int st = 0;
            char[] val = str.ToCharArray();
            int i = 0;
            while ((st < len) && (val[st] <= symbol))
            {
                i++;
                st++;
            }
            while ((st < len) && (val[len - 1] <= symbol))
            {
                i++;
                len--;
            }
            if (st == len)
                return "";
            return ((st > 0) || (len < str.Length)) ? str.Substring(st, str.Length - i) : str;
        }