How I Use The N' Switch In Stored Procedure

Any One Tell me how i can use N'Switch in SQL Server Stored Procedure .
When I use Such a this syntax i am encountered and stoped with a error.
the is below(Stoerd Prdocedure Code)
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CREATE proc sp_check_userpass(@username nvarchar(50),@password nvarchar(50),@first nvarchar(50),@last nvarchar(50),@email nvarchar(50),@stage int )as
declare @cnt int
begin
select @cnt=count(*) from member_info where (@username=username and @password=password)
if(@cnt=0)
begin
insert into atable(first,last,username,password,stage) values(@first,@last,@username,@password,@stage)
end
else
return @cnt
end
GO
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Other thing is that when exec this store proc it must be return a value return back to the @cnt but it is return only This( The command(s) Completed succefully).
Any One guide me how i can must be do .
i must clear it that i am using this query in ASP.NET SqlClient Object To Execute Query.
Thanx In Advance. ArQa