I just did a test and works for me
Sp...
CREATE PROCEDURE spSelect @name nvarchar(40)
AS
BEGIN
select *
from employees
where name =@name
END
Calling....
either spSelect N'بطری'
or EXECUTE spSelect @name = N'بطری'
You may have to set the following for you SQLcommand Object
parameter.SqlDbType = SqlDbType.NVarChar;