score:18
updated (post c# 7) answer
if using c# 7 or 8 then one could use the is keyword together with linq.all:
var result = comparison.all(item => item.value is null)
if using c# 9 then one could use the is not null together with linq.any:
var result = comparison.any(item => item.value is not null)
if using c# 9 then one could also use the is object or is {} together with linq.any:
var result = comparison.any(item => item.value is object)
all these options are somewhat equivalent. at least in terms of time complexity they are all o(n). i guess the "preferred" option simply depends on personal opinion.
original (pre c# 7) answer
using linq method of all:
var result = comparison.all(item => item.value == null)
basically what it does is to iterate all items of a collection and check a predicate for each of them. if one does not match - result is false
score:1
i'm not totally sure about the internal differences of all and exists, but it might be a good idea to just check whether one of the entries is not null and then negate the result:
var result = !comparison.exists(o => o.value != null);
i would expect this query to quit after the first non-null value was found and therefore to be a little more efficient.
update: from the enumerable.all documentation:
the enumeration of source is stopped as soon as the result can be determined.
therefore, using all will probably not result in the entire list getting processed after a non-null value has been found.
so the aforementioned possible performance gain is not likely to occur and both solutions probably do not differ.
score:4
you can check by this linq statement
var isnull = comparison.all(item => item.value == null);
Source: stackoverflow.com
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