Question

I have one question..

Which has more effective performance? Or which take less time to execute and Why?

session["var"].ToString()

or

(string)session["var"]

Answer 1

ToString() is a method and (string) is casting (Explicit). IMO casting is always fast

A cast operation between reference types does not change the run-time
type of the underlying object; it only changes the type of the value
that is being used as a reference to that object.

Source: Explicit Conversions

.ToString() can be called from any object. This method is inherited from object class and can be overloaded

.(string) is a cast, Its not a function call. It should be used when it is sure that the object is already in string, it will throw an exception when it can’t convert to string including null