Question

This works as expected:

byte b = 7;
var i = (int)b;

While this throws an InvalidCastException:

byte b = 7;
object o = b;
var i = (int)o;

Why does the cast fail from an object when the underlying type is still byte?

Answer 1

Because byte has an explicit conversion to int, but object does not.

If you tell the compiler the object is really a byte, then it will once again allow you to explicitly cast to int.

byte b = 7;
object o = b;
var i = (int)((byte)o);

References:

Casting and Type Conversions
byte