送上本人的一个LINQ多表关联动态条件查询解决方案（请大家指正）

第一步：
建立一个动态构建查询语句的类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Linq;
using System.Linq.Expressions;

namespace SJJ.DataAccess
{
    public static class linqWhere
    {
        public static Expression<Func<T, bool>> True<T>() { return f => true; }

        public static Expression<Func<T, bool>> False<T>() { return f => false; }

        public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)
        {
            var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
            return Expression.Lambda<Func<T, bool>>(Expression.Or(expr1.Body, invokedExpr), expr1.Parameters);
        }
        public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)
        {
            var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
            return Expression.Lambda<Func<T, bool>>(Expression.And(expr1.Body, invokedExpr), expr1.Parameters);
        }
    }
}

13 个解决方案

#1

第二步：

建立相关联的实体类：

using System;

namespace SJJ.WhereModel
{
    /// <summary>
    /// 家具频道·特价信息·评论
    /// </summary>
    [Serializable]
    public class furniture_bargain_review
    {

        #region 成员方法

        /// <summary>
        /// 评论时间·始
        /// </summary>
        public DateTime furniture_bargain_review_Date_begin { get; set; }
        /// <summary>
        /// 评论时间·末
        /// </summary>
        public DateTime furniture_bargain_review_Date_end { get; set; }
        /// <summary>
        /// 评论用户
        /// </summary>
        public string furniture_bargain_review_Name { get; set; }
        /// <summary>
        /// 电子邮件
        /// </summary>
        public string furniture_bargain_review_Email { get; set; }
        /// <summary>
        /// 评论内容
        /// </summary>
        public string furniture_bargain_review_Body { get; set; }

        #endregion

    }
}

#2

第三步：

开始调用


/// <summary>
        /// 根据条件查询所有信息
        /// </summary>
        /// <param name="bargainId">产品编号</param>
        /// <param name="modelQ">条件列表</param>
        /// <param name="pageSize">分页大小</param>
        /// <param name="pageIndex">当前页码</param>
        /// <param name="pageCount">总页数</param>
        /// <param name="Counts">总记录数</param>
        /// <returns></returns>
        public IQueryable GetList(int bargainId,SJJ.WhereModel.furniture_bargain_review modelQ, int pageSize, int pageIndex, out int pageCount, out int Counts)
        {
            //初始化数据库连接字符串·开始
            setConnectionString();
            //初始化数据库连接字符串·结束
            pageCount = Counts = 0;
            var objQueryWhere = linqWhere.True<SJJ.LINQ.furniture_bargain_review>();

            #region 生成判断条件

            if (modelQ != null)
            {
                //评论·时间
                if (modelQ.furniture_bargain_review_Date_begin != null && modelQ.furniture_bargain_review_Date_end != null)
                {
                    objQueryWhere = objQueryWhere.And(p => p.furniture_bargain_review_Date >= modelQ.furniture_bargain_review_Date_begin);
                    objQueryWhere = objQueryWhere.And(p => p.furniture_bargain_review_Date <= modelQ.furniture_bargain_review_Date_end);
                }
                //评论·名称
                if (!string.IsNullOrEmpty(modelQ.furniture_bargain_review_Name))
                {
                    objQueryWhere = objQueryWhere.And(p => p.furniture_bargain_review_Name.Contains(modelQ.furniture_bargain_review_Name));
                }
                //评论·Email
                if (!string.IsNullOrEmpty(modelQ.furniture_bargain_review_Email))
                {
                    objQueryWhere = objQueryWhere.And(p => p.furniture_bargain_review_Email.Contains(modelQ.furniture_bargain_review_Email));
                }
                //评论·内容
                if (!string.IsNullOrEmpty(modelQ.furniture_bargain_review_Body))
                {
                    objQueryWhere = objQueryWhere.And(p => p.furniture_bargain_review_Body.Contains(modelQ.furniture_bargain_review_Body));
                }                
            }

            #endregion 生成判断条件

            var localTable = (from objTableA in objDataContext.furniture_bargain_review.Where(objQueryWhere)
                              where objTableA.furniture_bargain_Id == bargainId
                              join objTableB in objDataContext.furniture_bargain on objTableA.furniture_bargain_Id equals objTableB.furniture_bargain_Id
                              select new
                              {
                                  objTableA.furniture_bargain_review_Id,
                                  objTableA.furniture_bargain_review_Date,
                                  objTableB.furniture_bargain_Id,
                                  objTableB.furniture_bargain_Name,
                                  objTableA.furniture_bargain_review_Name,
                                  objTableA.furniture_bargain_review_Email,
                                  objTableA.furniture_bargain_review_Ip,
                                  objTableA.furniture_bargain_review_Body
                              }).OrderByDescending(p => p.furniture_bargain_review_Date);
            Counts = localTable.Count();
            if (Counts % pageSize != 0)
            {
                pageCount = Counts / pageSize + 1;
            }
            else
            {
                pageCount = Counts / pageSize;
            }
            return localTable.Skip((pageIndex - 1) * pageSize).Take(pageSize);
        }

#3

以上是本人的一个解决方案
还大家指正其中的不足之处
最好能改进，呵

#4

mark

#5

mark

#6

不知道是我做得不好？
还是那位高人有更好的解决方案？
希望能分享……

#7

郁闷，没做过。。。

#8

楼主的动态查询类怎么和一个老外写的一模一样啊。。。。

#9

mark

#10

学习了  

#11

ding

#12

mark,收藏了。。。。。。。。。

#13

查询类是老外写的