Using StringCollection specified in Application Settings in a LINQ-to-Entities Query
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27-04-2021 - |
문제
In my application, I have Property Setting which is of type String.Collections.Specialized.StringCollection. It contains a list of customer codes such as MSFT, SOF, IBM etc. I'm trying to use this in a Linq-to-Entities query in the where clause:
var ShippedOrders = dbcontext.Orders
.Where(s=>(s.Status.Description.Equals("Shipped") && !Properties.Settings.Default.CustomersToExclude.Contains(s.CustomerCode)));
This fails as Contains is not recognized by Linq-to-Entities with a message similar to:
"LINQ-to-Entities does not recognize the method Contains...."
How do I revise the code above to avoid this error?
해결책
Since your question is tagged as C# 4 use a List<string>
instead (StringCollection
is ancient) and your query should work. Also you should resolve your list reference outside your query:
List<string> customersToExclude = ..
var ShippedOrders = dbcontext.Orders
.Where(s=>(s.Status.Description.Equals("Shipped")
&& !customersToExclude.Contains(s.CustomerCode)));
Edit:
Just copy your customers to an array and use that:
var customerstoExclude = new string[Properties.Settings.Default.CustomersToExclude.Count];
myProperties.Settings.Default.CustomersToExclude.CopyTo(customerstoExclude, 0);
다른 팁
A shorter path is
myProperties.Settings.Default.CustomersToExclude.Cast<string>().Contains(blah);
That's a handy trick for any situation where a collection isn't inherently LINQ-aware.
This is answered in a related question. EF4 apparently supports Contains directly, though, so that'd be my prefered solution... :)