哪种来看下俺的错在哪里呀~~

“/”应用程序中的服务器错误。
--------------------------------------------------------------------------------未找到任何可识别的数字。 
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。 异常详细信息: System.FormatException: 未找到任何可识别的数字。源错误: 
行 151:            strSql.Append(" where Name='" + UserName+"' and PassWord='"+PassWord+"'");
行 152:
行 153:            return DbHelperSQL.GetSingle(strSql.ToString());
行 154:            //{
行 155:            //    return Convert.ToInt32(DbHelperSQL.GetSingle(strSql.ToString()));
 
代码: /// <summary>
        /// 验证登录
        /// </summary>
        public int  GetUserID(string UserName,string PassWord)
        {
            StringBuilder strSql = new StringBuilder();
            strSql.Append("select ID  ");
            strSql.Append(" FROM UserBase ");
           
            strSql.Append(" where Name='" + UserName+"' and PassWord='"+PassWord+"'");            if (DbHelperSQL.GetSingle(strSql.ToString()) != null)
            {
                return Convert.ToInt32(DbHelperSQL.GetSingle(strSql.ToString()));
            }
            else 
            {
                return 0;
            }
        }
 /// <summary>
        /// 执行一条计算查询结果语句，返回查询结果（object）。
        /// </summary>
        /// <param name="SQLString">计算查询结果语句</param>
        /// <returns>查询结果（object）</returns>
        public static object GetSingle(string SQLString)
        {
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                using (SqlCommand cmd = new SqlCommand(SQLString, connection))
                {
                    try
                    {
                        connection.Open();
                        object obj = cmd.ExecuteScalar();
                        if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
                        {
                            return null;
                        }
                        else
                        {
                            return obj;
                        }
                    }
                    catch (System.Data.SqlClient.SqlException e)
                    {
                        connection.Close();
                        throw e;
                    }
                }
            }
        }