Can I unbox an integer with a cast in XAML?

Question

I've hit a case in which I have a class that returns type object that I happen to know is merely a boxed int value. The control I am using can bind to an int property or a double property but it cannot bind to an object that is a boxed int or double. I have to work around this limitation. I'd like to do so in a very simple manner.

Edited to add: The exception that occurs when I try to do this is System.NotSupportedException with the message DoubleConverter cannot convert from System.Int32

So is there a way to make a cast to int or double in XAML that is the equivalent of an unboxing operation? I already know how to cast a reference type in XAML so I can access some specific, derived-class property. But I am having trouble with this one because int is not a type with properties.

Below is the class (a simplified version). It represents a ranged set of integers or doubles or even other types for which "min" and "max" values would be meaningful. So it has to return them all as object. Regardless, all 3 properties will return the same underlying type in the boxed value, be it double or int or something else.

public class Parameter
{
    virtual object Lower      { get; }     
    virtual object Upper      { get; }   
    virtual object Value      { get; set; } 
}

I bind to the control like this

<tk:RadNumericUpDown MinWidth="100"
    IsInteger="True"
    Value="{Binding Value, Mode=TwoWay}"
    Minimum="{Binding Lower, Mode=OneWay}"
    Maximum="{Binding Upper, Mode=OneWay}"
    />

Now if I know that the Lower property is an int, can I bind it with some sort of XAML cast? I've tried a few things

Minimum="{Binding Lower(sys:Int32), Mode=OneWay}"
Minimum="{Binding Lower.(sys:Int32), Mode=OneWay}"

I didn't expect any of these to work and they didn't. But the syntax (if there is one) eludes me. About the only way I can get this to work is to define a separate property in the class that returns the Lower as an int value

Is there a way to do an unboxing cast in XAML?