Linq存储库和GetTable< T>() [英] Linq repository and GetTable<T>()

问题描述

我遵循相当标准的L2S存储库模式，将以下内容用作方法之一

I'm following the fairly standard L2S repository pattern, using the following as one of the methods

public IEnumerable<T> GetAllByFilter(Func<T, bool> expression)
 {
     return _dataContext.GetTable<T>().Where(expression);
 }

我很想知道对GetTable的调用似乎是从字面上获取表的，而Where表达式大概是在内存中求值的.

I'm a bit miffed to see that the call to GetTable appears to literally get the table, with the Where expression presumably evaluated in-memory afterwards.

像这样的简单呼叫

var order = GetAllByFilter(o => o.OrderNumber == 1);

应该只返回一条记录的

正在获取整个50000条记录数据库.

which should only ever return one record, is fetching the entire 50000 record database.

Linq通常这么不好吗?还是我错过了什么?

Is Linq normally this bad? Or am I missing something?

推荐答案

更改:

public IEnumerable<T> GetAllByFilter(Func<T, bool> expression)
{
    return _dataContext.GetTable<T>().Where(expression);
}

收件人:

public IQueryable<T> GetAllByFilter(Expression<Func<T, bool>> expression)
{
    return _dataContext.GetTable<T>().Where(expression);
}

这将使用Queryable(即SQL)而不是Enumerable(即本地)，因此效果会更好.

This will use Queryable (i.e. SQL) instead of Enumerable (i.e. local) and therefore will perform much better.

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