Nullable types for a property value in a custom profile provider, is this possible?

Hi,
I'm just implementing a custom profile provider, and want to use a nullable type to a property value, for example:
        <profile ... >
            <providers>
                ...
            </providers>
 
            <properties>
                <clear />
                <add name="ProjectID" type="int?" allowAnonymous="false" />
            </properties>           
        </pro ...