[英]get count in linq query
我想在linq查询中获得计数,但在不比较where条件下的日期的情况下它的工作正常,但是在比较日期后它给出了异常。
public static IList GetAllCategoryData()
{
using (var objEntity = new BlueCouponEntities())
{
return (from TBL in objEntity.CategoryMasters.AsEnumerable()
let IIT = TBL.CategoryImageTransactions
select new
{
TBL.CategoryID,
TBL.CategoryName,
CategoryCount = objEntity.OfferCategoryMasters.Where(Lg => Lg.CategoryID == TBL.CategoryID && Lg.OfferMaster.EndDate > DateTime.Now.Date).Count(),
}
).ToList();
}
}
错误是:指定的类型成员; Date; LINQ to Entities不支持。 仅支持初始化程序,实体成员和实体导航属性。
您必须使用EntityFunctions.TruncateTime
来获取DateTime的Date部分
using (var objEntity = new BlueCouponEntities())
{
return (from TBL in objEntity.CategoryMasters.AsEnumerable()
let IIT = TBL.CategoryImageTransactions
select new
{
TBL.CategoryID,
TBL.CategoryName,
CategoryCount = objEntity.OfferCategoryMasters.Where(Lg => Lg.CategoryID == TBL.CategoryID && Lg.OfferMaster.EndDate > EntityFunctions.TruncateTime(DateTime.Now)).Count(),
}
).ToList();
}
由于DateTime.Now现在是常量,因此您也可以这样写
using (var objEntity = new BlueCouponEntities())
{
DateTime now = DateTime.Now.Date;
return (from TBL in objEntity.CategoryMasters.AsEnumerable()
let IIT = TBL.CategoryImageTransactions
select new
{
TBL.CategoryID,
TBL.CategoryName,
CategoryCount = objEntity.OfferCategoryMasters.Where(Lg => Lg.CategoryID == TBL.CategoryID && Lg.OfferMaster.EndDate > now).Count(),
}
).ToList();
}
它与Count()函数无关。 如异常所示,它是一个DateTime问题。 使用DbFunctions.TruncateTime (从EntityFunctions.TruncateTime
不推荐使用EntityFunctions.TruncateTime )
public static IList GetAllCategoryData()
{
using (var objEntity = new BlueCouponEntities())
{
return (from TBL in objEntity.CategoryMasters.AsEnumerable()
let IIT = TBL.CategoryImageTransactions
select new
{
TBL.CategoryID,
TBL.CategoryName,
CategoryCount = objEntity.OfferCategoryMasters.Where(Lg => Lg.CategoryID == TBL.CategoryID && EntityFunctions.TruncateTime(Lg.OfferMaster.EndDate) > EntityFunctions.TruncateTime(DateTime.Now.Date)).Count(),
}
).ToList();
}
}
添加以下行:
var today = DateTime.Now.Date;
然后使用今天而不是DateTime.Now.Date进入linq查询。
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