如果通过通用方法调用,Linq不会延迟加载吗? [英] Linq does not lazy load if invoked via generic method?
问题描述
所以,我有一个方法:我在一个带孔的序列中计算一个数字,这个数字应该是第一个孔或max()
so, i have a method: I'm counting a number in a sequence with holes, this number should be the first hole or max()
public static int GetRegisterNumber<T>(this IQueryable<T> enumerable, Func<T, bool> whereFunc, Func<T, int?> selectFunc)
{
var regNums = enumerable.OrderBy(selectFunc).Where(whereFunc).ToArray();
if (regNums.Count() == 0)
{
return 1;
}
for (int i = 0; i < regNums.Count(); i++)
{
if (i + 1 != regNums[i])
{
return regNums[i].Value + 1;
}
}
return regNums.Last().Value + 1;
}
我使用它的方式是:
var db = new SomeDataContext();
db.Goals.GetRegisterNumber(g => g.idBudget == 123, g => g.RegisterNumber);
因此,我希望从linq中获得一些查询,例如:
So, i expect from linq some query like:
SELECT [t0].[id], [t0].[tstamp], [t0].[idBudget], [t0].[RegisterNumber], FROM [ref].[GoalHierarchy] AS [t0] WHERE [t0].[idBudget] = 123 ORDER BY [t0].[RegisterNumber]
相反,我得到了:
SELECT [t0].[id], [t0].[tstamp], [t0].[idBudget], [t0].[RegisterNumber], FROM [ref].[GoalHierarchy] AS [t0]
因此linq会获取所有表数据,然后对其进行过滤,但是这种行为是不可接受的,因为该表包含许多数据.有什么解决办法吗?
So linq gets ALL the table data and then filters it, but that behavior is not acceptable, because the table contains much data. Is there any solution?
推荐答案
更改您的方法签名,如下所示:
Change your method signature to look like this:
public static int GetRegisterNumber<T>(this IQueryable<T> enumerable, Expression<Func<T, bool>> whereFunc, Expression<Func<T, int?>> selectFunc)
这样,它将为IQueryable<T>
调用适当的扩展方法.如果只有Func<TSource, bool>
,它将为IEnumerable<T>
调用扩展方法.
This way it will call the appropriate extension methods for IQueryable<T>
. If you only have a Func<TSource, bool>
, it will call the extension method for IEnumerable<T>
.
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