linq2sql中的简单Eager / Lazy加载示例
有没有人在linq2sql中有一个简单的代码示例来演示Eager Loading和Lazy Loading之间的区别?
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延迟加载:对于给定的实体,它的关联集合在首次加载时可能为空,但是当首次迭代这些集合时,LINQ to SQL会在加载后触发查询以加载这些集合,然后该集合可用于将来使用而无需其他查询:
var query = from o in db.GetTable
() //db is the datacontext select o; foreach(Order o in query) { foreach(OrderDetail d in o.OrderDetails)//Deferred loading { //Do something on these collections } }
OrderDetails
仅在迭代时加载,因此如果从不迭代OrderDetatils
则永远不会执行相应的查询。
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Eager Loading:立即加载所有引用实体的关联集合,例如LINQ to SQL将自动为所有已检索的订单带来所有
OrderDetails
DataLoadOptions op = new DataLoadOptions(); op.LoadWith
(o => o.OrderDetails); db.LoadOptions = op; var query = from o in db.GetTable () select o; foreach(Order o in query) { //Order details are eager loaded; additional queries are not needed foreach(OrderDetail d in o.OrderDetails) { //do something } }
请注意: 延迟执行是LINQfunction,但延迟加载是LINQ to SQLfunction