C＃Linq查询返回类型到字典

Question

I have a linq query below. I have a similar query in 3 other places which is obviously not great. So I want to pass the tfID to a method. I know you cannot pass var as a parameter to a method.

 var tfID = from orderItem in _orderBlock.Orders
                            join assetItem in tfEntity.AssetDetails on orderItem.Security.ID equals assetItem.sISIN
                            where orderItem.IdenitfierUsed == "I"
                            where assetItem.iSkeletal == 1
                            select new { orderItem, assetItem }; 

I wanted to change the query above to something like below. However error message I get is "cannot complicity convert type 'System.Collections.Generic.IEnumerable to 'System.Collections.Generic.Dictionary' An explicit conversion exists (are you missing a cast).

Dictionary<Order, AssetDetail> ordersDictionary = new Dictionary<Order, AssetDetail>();

        ordersDictionary = from orderItem in _orderBlock.Orders
                            join assetItem in tfEntity.AssetDetails on orderItem.Security.ID equals assetItem.sISIN
                            where orderItem.IdenitfierUsed == "I"
                            where assetItem.iSkeletal == 1
                            select new { orderItem, assetItem };

Answer 1

Use ToDictionary

Dictionary<Order, AssetDetail> ordersDictionary =  
    (from orderItem in _orderBlock.Orders
    join assetItem in tfEntity.AssetDetails on orderItem.Security.ID equals assetItem.sISIN
    where orderItem.IdenitfierUsed == "I"
    where assetItem.iSkeletal == 1
    select new { orderItem, assetItem })
    .ToDictionary(x => x.orderItem, x => x.assetItem);

Answer 2

ordersDictionary = (from orderItem in _orderBlock.Orders
                    join assetItem in tfEntity.AssetDetails on orderItem.Security.ID 
                    equals assetItem.sISIN
                        where orderItem.IdenitfierUsed == "I"
                        where assetItem.iSkeletal == 1
                        select new { orderItem, assetItem }
                   ).ToDictionary(x=>x.orderItem, x=>x.assetItem);

Answer 3

You can use the ToDictionary() method to turn the result into a dictionary. Ie

Dictionary<Order, AssetDetail> ordersDictionary = new Dictionary<Order, AssetDetail>();

    ordersDictionary = (from orderItem in _orderBlock.Orders
                        join assetItem in tfEntity.AssetDetails on orderItem.Security.ID equals assetItem.sISIN
                        where orderItem.IdenitfierUsed == "I"
                        where assetItem.iSkeletal == 1
                        select new { orderItem, assetItem }).ToDictionary(key => //the key, value => the value);

Answer 4

I know you cannot pass var as a parameter to a method.

Not true - var is not (necessarily) an anonymous type - it just lets the compiler decide what the type is.

All you need to do is add ToDictionary() :

var tfID = (from orderItem in _orderBlock.Orders
                        join assetItem in tfEntity.AssetDetails on orderItem.Security.ID equals assetItem.sISIN
                        where orderItem.IdenitfierUsed == "I"
                        where assetItem.iSkeletal == 1
                        select new { orderItem, assetItem })
            .ToDictionary(i => orderItem, i => assetItem); 

tfID will then be a Dictionary<Order, AssetDetail>