C# Linq 选择列表中存在 IN (A,B,C) 的对象
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Linq select objects in list where exists IN (A,B,C)
提问by MartinS
I have a list of orders.
I want to select ordersbased on a set of order statuses.
我有一个列表orders。
我想orders根据一组订单状态进行选择。
So essentially select orders where order.StatusCode in ("A", "B", "C")
所以本质上 select orders where order.StatusCode in ("A", "B", "C")
// Filter the orders based on the order status
var filteredOrders = from order in orders.Order
where order.StatusCode.????????("A", "B", "C")
select order;
采纳答案by Tim Schmelter
Your status-codes are also a collection, so use Contains:
您的状态代码也是一个集合，因此请使用Contains：
var allowedStatus = new[]{ "A", "B", "C" };
var filteredOrders = orders.Order.Where(o => allowedStatus.Contains(o.StatusCode));
or in query syntax:
或在查询语法中：
var filteredOrders = from order in orders.Order
where allowedStatus.Contains(order.StatusCode)
select order;
回答by Tim Schmelter
var statuses = new[] { "A", "B", "C" };
var filteredOrders = from order in orders.Order
where statuses.Contains(order.StatusCode)
select order;
回答by Soner G?nül
回答by Alexander Christov
NB:this is LINQ to objects, I am not 100% sure if it work in LINQ to entities, and have no time to check it right now. In fact it isn't too difficult to translate it to x in [A, B, C]but you have to check for yourself.
注意：这是 LINQ to objects，我不是 100% 确定它是否在 LINQ to entity 中工作，现在没有时间检查它。事实上，在 [A, B, C] 中将其转换为x并不太难，但您必须自己检查。
So, instead of Containsas a replacement of the ????in your code you can use Anywhich is more LINQ-uish:
所以，而不是包含作为替代???? 在您的代码中，您可以使用Any更像 LINQ：
// Filter the orders based on the order status
var filteredOrders = from order in orders.Order
where new[] { "A", "B", "C" }.Any(s => s == order.StatusCode)
select order;
It's the opposite to what you know from SQL this is why it is not so obvious.
这与您从 SQL 中知道的相反，这就是为什么它不是那么明显。
Of course, if you prefer fluent syntax here it is:
当然，如果你更喜欢这里的流畅语法，它是：
var filteredOrders = orders.Order.Where(order => new[] {"A", "B", "C"}.Any(s => s == order.StatusCode));
Here we again see one of the LINQ surprises (like Joda-speech which puts select at the end). However it is quite logical in this sense that it checks if at least one of the items (that is any) in a list (set, collection) matches a single value.
在这里，我们再次看到 LINQ 的一个惊喜（如 Joda-speech 将 select 放在最后）。然而，从这个意义上说，它检查列表（集合、集合）中的至少一个项目（即any）是否与单个值匹配是非常合乎逻辑的。
回答by Balvinder Singh
Just be careful, .Contains()will match any substring including the string that you do not expect. For eg. new[] { "A", "B", "AA" }.Contains("A")will return you both A and AA which you might not want. I have been bitten by it.
请注意，.Contains()将匹配任何子字符串，包括您不期望的字符串。例如。new[] { "A", "B", "AA" }.Contains("A")将返回您可能不想要的 A 和 AA。我被它咬了。
.Any()or .Exists()is safer choice
.Any()或者.Exists()更安全的选择
