difference between List<T> and List<T>=new List<T> in c# -

i sorry if question silly, new c#

i want know exact difference between when create list variable this

list<t> lststudents; 

and when create list this

list<t>= new list<t>(); 

i found out if create variable without intializing object it, still able add new objects, if difference between 2 let me explain scenario code trying

 list<product> product = new list<product> {                                          new product() { productid = 1, productname = "a" }                                         ,  new product() { productid = 2, productname = "b" }                                         ,  new product() { productid = 3, productname = "c" }                                         ,  new product() { productid = 4, productname = "d" }                                         ,  new product() { productid = 5, productname = "e" }                                     }; 

now if add variable this

 list<product> p = product; 

i still able add objects in variable

  p.add(new product { productid = 3 }); 

please clarify doubt.

thank

i sorry may doing wrong in code

 public class students     {         public string name { get; set; }         public int studentid { get; set; }           }    list<product> product = new list<product> {                                          new product() { productid = 1, productname = "a" }                                         ,  new product() { productid = 2, productname = "b" }                                         ,  new product() { productid = 3, productname = "c" }                                         ,  new product() { productid = 4, productname = "d" }                                         ,  new product() { productid = 5, productname = "e" }                                     };               list<product> p = product;             p.add(new product { productid = 3 }); 

when run 6 items instead of 5

now if add variable this

list<product> p = product; 

i still able add objects in variable

yes, because the variables referencing same list. if @ p notice added item reflected there well.

i found out if create variable without intializing object it, still able add new objects

not true - if this:

list<t> lststudents; 

and try add something:

lststudents.add(...); 

you compiler error if list declaration within method, , nullreferenceexception if class member because lststudents not referencing (it "null" reference).

when run 6 items instead of 5

yes because list referenced product contained 5 elements, p references same list, , added one.

lists reference types, meaning "copying" value of 1 variable variable copies reference underlying object. it's akin pointers in older languages c.