根据转入的条件拼凑SQL条件语句

 /// <summary>
 /// SQL的条件符号枚举。dengyu表示“等于”,dayu表示“大于”,dayuOrdengyu表示“大于并且等于”,xiaoyuOrdengyu表示“小于并且等于”,inType表示“in”,like表示"like"
/// </summary>
        enum OperaTeype { dengyu,dayu, xiaoyu, dayuOrdengyu, xiaoyuOrdengyu, inType, like };

 /// <summary>
        /// 根据转入的条件拼凑SQL条件语句
        /// </summary>
        /// <param name="type">条件符号。如大于，等于等</param>
        /// <param name="value">字段的值</param>
        /// <param name="filed">字段的名称</param>
        /// <param name="yihao">是否加引号</param>
        /// <returns></returns>
        private string GetReturnString(OperaTeype type, object value,string filed,bool yihao)
        {
            string strStart=" and ";
            if (value == null) 
            {
                return string.Empty;
            }
            if (value.ToString().Length <= 0)
            {
                return string.Empty;
            }
            if (yihao == true)
            {
                value = "'" + value + "'";
            }
           
            if ((type == OperaTeype.dayu)) 
            {             
                    return string.Format("{0}{1}>{2}", strStart, filed, value);
                
            }
            if ((type == OperaTeype.dengyu))
            {
                return string.Format("{0}{1}={2}", strStart, filed, value);
            }
            if ((type == OperaTeype.xiaoyu))
            {
                return string.Format("{0}{1}<{2}", strStart, filed, value);
            }
            if ((type == OperaTeype.dayuOrdengyu))
            {
                return string.Format("{0}{1}>={2}", strStart, filed, value);
            }
            if ((type == OperaTeype.xiaoyuOrdengyu))
            {
                return string.Format("{0}{1}<={2}", strStart, filed, value);
            }
            if ((type == OperaTeype.inType))
            {
                return string.Format("{0}{1} in ({2})", strStart, filed, value);
            }
            if ((type == OperaTeype.like))
            {
                return string.Format("{0}{1} like '%{2}%'", strStart, filed, value);
            }
            return string.Empty;
        }