How to compare nullable types?
I have a few places where I need to compare 2 (nullable) values, to see if they're t开发者_开发知识库he same.
I think there should be something in the framework to support this, but can't find anything, so instead have the following:
public static bool IsDifferentTo(this bool? x, bool? y)
{
return (x.HasValue != y.HasValue) ? true : x.HasValue && x.Value != y.Value;
}
Then, within code I have if (x.IsDifferentTo(y)) ...
I then have similar methods for nullable ints, nullable doubles etc.
Is there not an easier way to see if two nullable types are the same?
Update:
Turns out that the reason this method existed was because the code has been converted from VB.Net, where Nothing = Nothing returns false (compare to C# where null == null returns true). The VB.Net code should have used .Equals...
instead.
C# supports "lifted" operators, so if the type (bool?
in this case) is known at compile you should just be able to use:
return x != y;
If you need generics, then EqualityComparer<T>.Default
is your friend:
return !EqualityComparer<T>.Default.Equals(x,y);
Note, however, that both of these approaches use the "null == null
" approach (contrast to ANSI SQL). If you need "null != null
" then you'll have to test that separately:
return x == null || x != y;
Nullable.Equals<T>
?
if (x.Equals(y))
You can use the static Equals method on System.Object:
var equal = object.Equals(objA, objB);
Use Compare:
http://msdn.microsoft.com/en-us/library/dxxt7t2a.aspx
Just use ==
, or .Equals()
.
I wanted to find how to compare two nullable int on C#, but I always get this link after search, so if someone needs to compare exactly two nullable int, then this can be helpful
a.GetValueOrDefault(int.MinValue).CompareTo(b.GetValueOrDefault(long.MinValue));
(x?? 0).Equals(y)
will handle null as well as equals.
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