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

  /// 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);