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这里是我的代码快照正常工作:Linq查询无法转换为SQL:如何优化代码?
var q1 = from msg in db.GetTable<Message>()
.Where(msg0 => ...)
from mt in db.GetTable<MessageTo>()
.Where(mt0 => ...)
.DefaultIfEmpty()
select new { msg, mt }
;
AgeTypeEnum eAgeType = (AgeTypeEnum)age.Value;
switch (eAgeType)
{
case AgeTypeEnum.Invalid:
break;
case AgeTypeEnum.LastWeek:
q1 = q1.Where(q => q.msg.CreatedDate >= DateTime.Now.AddDays(-7));
break;
case AgeTypeEnum.LastMonth:
q1 = q1.Where(q => q.msg.CreatedDate >= DateTime.Now.AddMonths(-1) && q.msg.CreatedDate < DateTime.Now.AddDays(-7));
break;
case AgeTypeEnum.CurrentSeason:
q1 = q1.Where(q => q.msg.CreatedDate >= Season.CurrentSeason.FirstPlayedDay.RealDate && q.msg.CreatedDate < DateTime.Now.AddDays(-7));
break;
case AgeTypeEnum.LastSeason:
q1 = q1.Where(q => q.msg.CreatedDate >= Season.PreviousSeason.FirstPlayedDay.RealDate && q.msg.CreatedDate < Season.CurrentSeason.FirstPlayedDay.RealDate);
break;
case AgeTypeEnum.PreviousSeasons:
q1 = q1.Where(q => q.msg.CreatedDate < Season.PreviousSeason.FirstPlayedDay.RealDate);
break;
default:
throw new MyException("'{0}' age type is not supported", eAgeType);
}
return q1.Select(q => new {MessageObj = q.msg}).ToList();
此代码工作正常,但它是相当位。并包含潜在的可重用逻辑。我想优化它以下列方式:
Func<Message, bool> qAgeFilter;
AgeTypeEnum eAgeType = (AgeTypeEnum)age.Value;
switch (eAgeType)
{
case AgeTypeEnum.Invalid:
qAgeFilter = null;
break;
case AgeTypeEnum.LastWeek:
qAgeFilter = msg => msg.CreatedDate >= DateTime.Now.AddDays(-7);
break;
case AgeTypeEnum.LastMonth:
qAgeFilter = msg => msg.CreatedDate >= DateTime.Now.AddMonths(-1) && msg.CreatedDate < DateTime.Now.AddDays(-7);
break;
case AgeTypeEnum.CurrentSeason:
qAgeFilter = msg => msg.CreatedDate >= Season.CurrentSeason.FirstPlayedDay.RealDate && msg.CreatedDate < DateTime.Now.AddDays(-7);
break;
case AgeTypeEnum.LastSeason:
qAgeFilter = msg => msg.CreatedDate >= Season.PreviousSeason.FirstPlayedDay.RealDate && msg.CreatedDate < Season.CurrentSeason.FirstPlayedDay.RealDate;
break;
case AgeTypeEnum.PreviousSeasons:
qAgeFilter = msg => msg.CreatedDate < Season.PreviousSeason.FirstPlayedDay.RealDate;
break;
default:
throw new MyException("'{0}' age type is not supported", eAgeType);
}
if (qAgeFilter != null)
{
q1 = q1.Where(q => qAgeFilter(q.msg));
}
事实上,不同的是,而不是修改Q1对象(查询本身),我结合新的委托和查询表达式中使用它之后。
当试图执行优化的代码我收到异常:
“调用(值(vfm_elita.ServiceLayer.DataLogicLayer.Messages.MessagesExtension + <> C_ DisplayClass21 + <>Ç _DisplayClass2c).qAgeFilter, q.msg)'无法转换为SQL。
问题:
有什么错我的代码?
你会如何建议,以便提取可重复使用的逻辑组成“过滤器”授人以优化的源代码?
谢谢
附:我使用ASP.NET 4.0,MySQL 5.0,BLToolKit作为数据库访问引擎。
谢谢!这有帮助。关键是不是创建一个Func,而是一个将更多逻辑添加到IQueryable对象中的扩展方法。 – Budda