[英]Entity Framework Search functionality with Dynamic SQL WHERE clause
嗨,大家好,我使用Dynamic SQL进行搜索查询,我曾经将WHERE
& AND
子句逐段附加并形成一条语句,为此我最近来到了下面,这真是太棒了
Select * From tblEmployees
where EmployeeName = Coalesce(@EmployeeName, EmployeeName) AND
Department = Coalesce(@Department, Department ) AND
Designation = Coalesce(@Designation, Designation) AND
JoiningDate >= Coalesce(@StartDate, JoiningDate) AND
JoiningDate <= Coalesce(@EndDate, JoiningDate) AND
Salary >= Coalesce(@Salary, Salary)
现在的问题是,因为我实现了实体框架,所以我需要使用Linq查询实现相同的功能。 我有目前无法处理的可为空的字节类型和可为空的布尔值
就像Coalesce
一样,我的愚蠢尝试是&& (s.Floors == deal.Floors.HasValue ? null : s.Floors)
下面的代码不符合任何结果
[HttpPost]
public ActionResult Results(Deal deal, bool exactMatch)
{
List<Deal> deals;
if (exactMatch)
{
deals = dataBase.Deals.Where(s =>
(s.OwnerName.Contains(deal.OwnerName) || s.OwnerName == null)
&& (s.Rooms == deal.Rooms || s.Rooms == null)
&& (s.BathRooms == deal.BathRooms || s.BathRooms == null)
&& (s.Floors == deal.Floors || s.Floors == null)
&& (s.Builtin == deal.Builtin || s.Builtin == null)
&& (s.Kitchens == deal.Kitchens || s.Kitchens == null)
&& (s.DoubleUnit == deal.DoubleUnit || s.DoubleUnit == null)
&& (s.Corner == deal.Corner || s.Corner == null)
&& (s.Remarks.Contains(deal.Remarks) || s.Remarks == null)
).ToList();
}
else
{
deals = dataBase.Deals.Where(s =>
(s.OwnerName.Contains(deal.OwnerName) || s.OwnerName == null)
|| (s.Rooms == deal.Rooms || s.Rooms == null)
|| (s.BathRooms == deal.BathRooms || s.BathRooms == null)
|| (s.Floors == deal.Floors || s.Floors == null)
|| (s.Builtin == deal.Builtin || s.Builtin == null)
|| (s.Kitchens == deal.Kitchens || s.Kitchens == null)
|| (s.DoubleUnit == deal.DoubleUnit || s.DoubleUnit == null)
|| (s.Corner == deal.Corner || s.Corner == null)
|| (s.Remarks.Contains(deal.Remarks) || s.Remarks == null)
).ToList();
}
return View(deals);
}
表的值如下
id Bathroom Floors
1 1 2
2 1 4
3 2 6
4 3 1
我需要具有ID 1和2的结果,例如在前端用户中,我只想将浴室字段填充为“ 1”,而将地板字段保留为空
您正在测试表中的字段是否等于'deal'属性或该字段为空,而不是这样做:
s.Remarks.Contains(deal.Remarks) || deal.Remarks == null
如果这样做,它应该是等效的查询。
您也可以累积执行此操作。 例如,在完全匹配的情况下,您可以执行以下操作:
deals = dataBase.Deals;
if (deal.OwnerName != null)
deals = deals.Where(s => s.OwnerName.Contains(deal.OwnerName));
if (deal.Rooms != null)
deals = deals.Where(s => s.Rooms == deal.Rooms)
这样可以使查询结果更加有效。 有一种类似的方法可以通过使用联合对不完全匹配进行此操作。 我不了解语法。
不太一样。 在查询中, coalesce
是在参数上,然后将记录值作为默认值(如果为空)。 在您的C#lambda中,您正在检查参数是否与表值相同,然后检查表值是否为null
但这忽略了参数中具有null值的可能性。
例
SQL
Department = Coalesce(@Department, Department )
将会
(s.Department == deal.Department || deal.Department == null)
这不是你现在拥有的
(s.Department == deal.Department || s.Department == null)
如果您想复制COALESCE
表达式,现在可以用这种方式编写它,尽管我不确定它是否会降低效率/性能。
(s.Department == (deal.Department ?? s.Department))
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