Check if KeyValuePair exists with LINQ's FirstOrDefault
http://stackoverflow.com/questions/793897/check-if-keyvaluepair-exists-with-linqs-firstordefault
问题:
I have a dictionary of type
Dictionary<Guid,int>
I want to return the first instance where a condition is met using
var available = m_AvailableDict.FirstOrDefault(p => p.Value == 0)
However, how do I check if I'm actually getting back a KeyValuePair? I can't seem to use != or == to check against default(KeyValuePair) without a compiler error. There is a similar thread here that doesn't quite seem to have a solution. I'm actually able to solve my particular problem by getting the key and checking the default of Guid, but I'm curious if there's a good way of doing this with the keyvaluepair. Thanks
If you just care about existence, you could use ContainsValue(0)
or Any(p => p.Value == 0)
instead? Searching by value is unusual for a Dictionary<,>
; if you were searching by key, you could use TryGetValue
.
One other approach:
var record = data.Where(p => p.Value == 1)
.Select(p => new { Key = p.Key, Value = p.Value })
.FirstOrDefault();
This returns a class - so will be null
if not found.
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