To check if a value type is nullable I'm currently doing something like this:
int? i = null;
bool isNullable = i.GetType().ToString().Contains("System.Nullable");
Is there a more elegant way to do this?
views:
117answers:
3
+7
A:
if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>))
{
// it is a nullable type
}
This is how Microsoft recommends you Identify Nullable Types
w69rdy
2010-07-08 17:01:34
Wow - that's a strange recommendation for Microsoft to make given that there's a built-in method to do this. (See my answer.)
Jon Skeet
2010-07-08 17:04:53
Yeah it seems a bit more long winded. Looking at yours, could it be that it returns null if its not a nullable type and that although you can use it to check if a type is nullable it's not strictly meant for that purpose? (although it is quicker!)
w69rdy
2010-07-08 17:09:00
@w69wrdy: Well it gives more information than you require - but it gives you all the information you *do* require and in a simpler way. It's *very slightly* less efficient in the case where it's a nullable type, as it'll also get the generic type arguments... but I'd go for readability and simplicity any day.
Jon Skeet
2010-07-08 17:11:09
A:
int? i;
bool isNullable = i is Nullable;
Edit: Nevermind, this doesn't work.
TheSean
2010-07-08 17:01:57
This doesn't seem to work, I get this compiler warning:The given expression is never of the provided ('System.Nullable') type
RobSullivan
2010-07-08 17:06:37
@RobSullivan: Yes, it's checking for compatibility with the System.Nullable static class... which is never going to work. I've been assuming you've got an instance of `Type` btw - if you've got an *actual variable* with a concrete type then you already know the result...
Jon Skeet
2010-07-08 17:11:58
+12
A:
You can use Nullable.GetUnderlyingType(Type) - that will return null if it's not a nullable type to start with, or the underlying value type otherwise:
if (Nullable.GetUnderlyingType(t) != null)
{
// Yup, t is a nullable value type
}
Note that this uses the Nullable static class, rather than the Nullable<T> structure.
Jon Skeet
2010-07-08 17:02:33
+1 Id probably go with this one since its a lot cleaner, plus looking at Reflector, this also checks to make sure the type is not a generic type definition.
SwDevMan81
2010-07-08 17:10:40