CODEWITHSUNDEEP
c#genericsreflectionnullable
Paddy
Paddy

Reputation: 33867

Reflection - check all nullable properties have values

I have to loop through all the properties in a few classes and check any nullable properties to see if they have a value. How do I cast the value returned from propertyInfo.GetValue() to a generic nullable type so that I can check the HasValue property?

Code snipped for brevity:

foreach (PropertyInfo propInfo in this.GetType().GetProperties())
{
    if (<Snip: Check to see that this is a nullable type>)                                                                      
    {
           //How do i cast this properly in here to allow me to do:
           if(!((Nullable)propInfo.GetValue(this, null)).HasValue)
                  //More code here
    }
}

Upvotes: 19

Views: 11826

Answers (2)

Marc Gravell
Marc Gravell

Reputation: 1064114

note I'm assuming you mean Nullable<T>; if you mean Nullable<T> or a reference, then you already have it: object (from GetValue) - just check for null.

In the case of Nullable<T>; you can't cast to a single non-generic type (other than object) - but you don't need to; just check that it isn't null, since empty Nullable<T> is boxed to null, and GetValue returns object (hence it boxes the value).

if(Nullable.GetUnderlyingType(propInfo.PropertyType) != null) {
    // it is a Nullable<T> for some T
    if(propInfo.GetValue(this, null) != null) {
        // it has a value (it isn't an empty Nullable<T>)
    }
}

To clarify, Nullable is a static utility class that is completely separate to the Nullable<T> struct; so you don't cast to Nullable at all. As it happens, Nullable exists to provide things like the GetUnderlyingType that helps you work with Nullable<T>.

Upvotes: 32

AakashM
AakashM

Reputation: 63378

Since you've established that the property is of type Nullable<something>, you know its value has a HasValue property - so find that property by reflection and get its value.

Upvotes: 0

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