How to send multiple value with sql parameter for in()

Question

I guess it is simple but I couldn't figure it out. I want it for asp.net project.

Normally I use Int for sql parameter for one int value but I need it for in() statement.

alter procedure abc
  @id int

select * from tbl where id = @id

It works for one value,

alter procedure abc
  @id int -- how should I change it

select * from tbl where id in (@id)

that one which I want. And how can I send the values in asp.net c#. Normally I send int value, but I do not know either?