Unboxing object containing a value which is known to be assignable to an integer variable

If I have an object instance and I know it is actually a boxed integer, then I can simply cast it back to int like this:

object o = GetSomethingByName("foo"); 
int i = (int)o;

However, I don't actually know that the value is an integer. I only know that it can be assigned to an integer. For example, it could be a byte, and the above code would throw InvalidCastException in that case. I开发者_Go百科nstead I would have to do this:

object o = GetSomethingByName("foo"); 
int i = (int)(byte)o;

The value could also be a short, or something else which can be assigned to an int. How do I generalize my code to handle all those cases (without handling each possibility separately)?

Simply writing the question made me remember that there is a Convert class. This seems to work:

int i = Convert.ToInt32(o);

edit: but unfortunately, it will also do type conversions that I actually don't want, like parsing strings.

It is interesting to see how Convert.ToInt32 accomplishes the conversion:

    public static int ToInt32(object value) 
    {
        return value == null? 0: ((IConvertible)value).ToInt32(null); 
    } 

The trick is to cast the object to IConvertible.