Hello I need to know how to check if the object of the same type in C#.
Scenario:
class Base_Data{}
class Person : Base_Data { }
class Phone :
It depends on exactly what you're after. Using is or as (as shown in Darin's answer) will tell you if data refers to an instance of Person or a subtype. That's the most common form (although if you can design away from needing it, that would be even better) - and if that's what you need, Darin's answer is the approach to use.
However, if you need an exact match - if you don't want to take the particular action if data refers to an instance of some class derived from Person, only for Person itself, you'll need something like this:
if (data.GetType() == typeof(Person))
This is relatively rare - and it's definitely worth questioning your design at this point.