IsPrimitive doesn't include nullable primitive values

Question

I want to check if a Type is primitive or not and used the following code:

return type.IsValueType && type.IsPrimitive;

This works fine aslong as the primitive isnt nullable. For example int?, how can I check if the type is a nullable primitive type? (FYI: type.IsPrimitive == false on int?)

You need to identify nullable types and then drill into them to get the closed generic type out: http://stackoverflow.com/questions/5644587/find-type-of-nullable-properties-via-reflection `Nullable` isn't primitive, it's just a `struct` wrapper around other `struct` types with extra compiler support. — Adam Houldsworth, Jan 07 '14 at 14:18
That `int?` is a shorthand for `Nullable`, so it is correct that it is not reported as primitive. — Hans Keﬆing, Jan 07 '14 at 14:19
Nullables use the Generic type, which is not primitive by definition. Try the bellow suggestions :) — safejrz, Jan 07 '14 at 14:21
What are you actually trying to achieve? I'm asking because often there are better approaches than using reflection. — Tim Schmelter, Jan 07 '14 at 14:25
@TimSchmelter I am doing a deep clone and using the following (http://stackoverflow.com/a/11308879/2598770) but I want to modify it a bit and noticed that the check of IsPrimitive doesnt care about nullable ints. — Rand Random, Jan 07 '14 at 14:29

score 18 · Accepted Answer · answered Jan 07 '14 at 14:20

18

From MSDN:

The primitive types are Boolean, Byte, SByte, Int16, UInt16, Int32, UInt32, Int64, UInt64, IntPtr, UIntPtr, Char, Double, and Single.

So basically you should expect Nullable<Int32> to not be a primitive type.

You could use Nullable.GetUnderlyingType to "extract" Int32 from Nullable<Int32>.

answered Jan 07 '14 at 14:20

ken2k

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Thx for the Nullable.GetUnderlyingType, you dont happen to know a way to check a custom collection if its type.IsArray and than cast it to array if it is? For example: CustomList : IList, IList, IEnumerable – Rand Random Jan 07 '14 at 15:13
1

@RandRandom: This is a question-and-answer site; if that's your question then *post it as a question*, not as a comment. – Eric Lippert Jan 07 '14 at 15:47

Mike Perrenoud · Answer 2 · 2014-01-07T16:13:13.317

13

First you'll need to determine if it's Nullable<> and then you'll need to grab the nullable types:

if (type.IsGenericType
    && type.GetGenericTypeDefinition() == typeof(Nullable<>)
    && type.GetGenericArguments().Any(t => t.IsValueType && t.IsPrimitive))
{
    // it's a nullable primitive
}

Now, the aforementioned works, but not recursively. To get it to work recursively you'll need to put this into a method that you can call recursively for all types in GetGenericArguments. However, don't do that if it's not necessary.

That code may also be able to be converted to this:

if (type.GetGenericArguments().Any(t => t.IsValueType && t.IsPrimitive))
{
    // it's a nullable primitive
}

but the caveat there is that it may be a generic reference type and may not actually meet the definition of primitive for your needs. Again, remember, the aforementioned is more concise but could return a false positive.

edited Jan 07 '14 at 16:13

answered Jan 07 '14 at 14:20

Mike Perrenoud

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The type arguments to a nullable type are never nullable types. – Eric Lippert Jan 07 '14 at 14:33
@EricLippert, so there won't be any concern for recursion right? – Mike Perrenoud Jan 07 '14 at 14:59
1

Correct; the type arguments to `Nullable` at runtime are always straight-up value types, nothing fancy. – Eric Lippert Jan 07 '14 at 15:46

score 2 · Answer 3 · answered Jan 07 '14 at 14:20

The reason IsPrimitive fails on Nullable<int> (also known as int?) is that Nullable<int> is not a primitive. It is an instance of a generic class Nullable<T> with the type parameter of int.

You can check if a number is a nullable primitive by verifying that

It is a generic type,
Its generic type definition is Nullable<>, and
Its generic parameter type IsPrimitive.

IsPrimitive doesn't include nullable primitive values

3 Answers3

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