UserId in AspNet WebApi

Question

Hi friends.

 

I have successfully created  AspNet Web Api. I run the project, everything is ok, but i am confuse,why user Id is not generated serially i.e 1,2,3,4....... and also I am adding new user in database ,it is successfully added but not in last position in table.some time it add in last,sometime it is in middle, why is this happen?

 

please let me how to fixed this problem.