how we can free up some sources???

Question

the C# has garbage collector itself!!! and cleans useless variables and ....

Answer 1

when your application encapsulates unmanaged resources such as windows, files, and network connections, you should use destructors to free those resources. When the object is eligible for destruction, the garbage collector runs the Finalize method of the object

Answer 2

I guess we do not need to do that in C#. The destructor of every object is called automatically after the executing of a program and release any used resources.