intercept string

            string str = "Q://ABC/CBA/DBD";
            string path = @"DllDownLoad\1\da.txt";
            string u = @"DllDownLoad\";
            string strArray = str.Substring(0, str.IndexOf("DBD"));//输出strArray = Q://ABC/CBA/
            
            string p = path.Replace(u, string.Empty);//输出p = 1\da.txt