System.Linq.Dynamic 动态查询

• 安装
• VS->工具栏->NuGet程序管理器，System.Linq.Dynamic 
• 注意：

  使用动态查询必须先调用AsQueryable（）方法，因为动态扩展仅适用于实现IQueryable的集合。然后迭代结果与常规Linq一样。

• 动态查询

• using System.Linq.Dynamic

  /// <summary>

        /// 得到明细过滤条件
        /// </summary>
        /// <returns></returns>
        private string GetFilterWhere(out  List<object> paramList)
        {
            StringBuilder strWhere = new StringBuilder();
            object items;
            paramList = new List<object>();
            strWhere.AppendFormat("ProductionDate >=@{0}", paramList.Count);
            paramList.Add(Convert.ToDateTime(startDetailDateEdit.EditValue).Date);

            strWhere.AppendFormat(" && ProductionDate <=@{0}", paramList.Count);
            paramList.Add(Convert.ToDateTime(endDetailDateEdit.EditValue).Date);

            items = factoryDetailCheckedComboBoxEdit.Properties.GetCheckedItems();
            if (items != null && items.ToString() != string.Empty)
            {//数组参数，数组中是否包含实例相等的FactoryID值，“outerIt 代表实例”
                strWhere.AppendFormat(" && @{0}.Contains(outerIt.FactoryID)", paramList.Count);
                paramList.Add(UIHelper.ToArray(items.ToString()));
            }

            if (cbCustomer.HasValue())
            {
                strWhere.AppendFormat(" && CustomerID=@{0}", paramList.Count);
                paramList.Add(Convert.ToInt32(cbCustomer.SelectedValue));
            }

            if (txtMachineCode.Text.Trim() != string.Empty)
            {
                strWhere.AppendFormat(" && MachineCode.Contains(@{0})", paramList.Count);
                paramList.Add(txtMachineCode.Text.Trim());
            }

            return strWhere.ToString();
        }

        //查询
        List<object> paramList;
        string strWhere = GetFilterWhere(out paramList);

        //根据条件查询
        var query = sourceList.AsQueryable<FacilityEfficiencyReportInfo>().Where(strWhere, paramList.ToArray());
        var resultList = (from dynamic g in query select g).ToList();

• 动态分组

/// <summary>
        /// 得到分组的列名字符串
        /// </summary>
        /// <returns></returns>
        private string GetGroupNames()
        {
            StringBuilder groupName = new StringBuilder();
            if (m_FirstGroupFieldName != null)
            {
                groupName.Append(m_FirstGroupFieldName.Key);
            }
            if (m_SecondGroupFieldName != null)
            {
                if(groupName.Length>0)
                {
                    groupName.AppendFormat(",{0}", m_SecondGroupFieldName.Key);
                }
                else
                {
                    groupName.Append(m_SecondGroupFieldName.Key);
                }
            }
            if (m_ThirdGroupFieldName != null)
            {
                if(groupName.Length>0)
                {
                    groupName.AppendFormat(",{0}", m_ThirdGroupFieldName.Key);
                }
                else
                {
                    groupName.Append(m_ThirdGroupFieldName.Key);
                }
            }
            return groupName.ToString();
        }

object value;
            string groupNames = GetGroupNames();
            List<FacilityEfficiencyReportInfo> actualGroupList = new List<FacilityEfficiencyReportInfo>();//实际组列表,不区分日期
            if (string.IsNullOrEmpty(groupNames))
            {
                actualGroupList = groupList.GroupBy(m => m.ID).Select(g => new FacilityEfficiencyReportInfo { FinishedAmount = g.Sum(m => m.FinishedAmount), Workers = g.Sum(m => m.Workers), Duration = g.Sum(m => m.Duration), Sam = g.Average(m => m.Sam),List=g.ToList() }).ToList();
            }
            else
            {
                var query = groupList.AsQueryable()
                       .GroupBy(string.Format("new ({0})", groupNames), "it")
                       .Select("new(it.Key as Key, it as GroupList)");
                var tempGroupList = (from dynamic g in query select g).ToList();
                foreach (var g in tempGroupList)
                {//每一组合并成一个FacilityEfficiencyReportInfo实例，明细放入model.List列表
                    FacilityEfficiencyReportInfo newModel = null;
                    object test = g.Key;
                    foreach (FacilityEfficiencyReportInfo m in g.GroupList)
                    {
                        if (newModel == null)
                        {
                            newModel = m.Clone();
                            newModel.InitDate();
                            newModel.List = new List<FacilityEfficiencyReportInfo>();
                        }
                        newModel.List.AddRange(m.List);
                    }
                    actualGroupList.Add(newModel);
                }
            }

query = Contact.GetContactsList().AsQueryable().Where("@0.Contains(outerIt.Country)", newList<String>() { "Austria", "Poland" });

其中“outerIt”代表整理上下文：“联系人”列表。为此，我们应该定义一个“outerIt”关键字

query = Contact.GetContactsList().AsQueryable().Where("@0.Contains(outerIt.Country) && it.BirthDate.Year > @1", new List<string>() { "Austria", "Poland" }, 1955);