CREATE FUNCTION whichContinent 
(@Country nvarchar(15))
RETURNS varchar(30)
AS
BEGIN
declare @Return varchar(30)
select @return = case @Country
when 'Argentina' then 'South America'
when 'Belgium' then 'Europe'
when 'Brazil' then 'South America'
when 'Canada' then 'North America'
when 'Denmark' then 'Europe'
when 'Finland' then 'Europe'
when 'France' then 'Europe'
else 'Unknown'
end

return @return
end

print dbo.WhichContinent('France')

create table test
(Country varchar(15),
Continent as (dbo.WhichContinent(Country)))
insert into test (country) values ('USA')
insert into test (country) values ('France')

select * from test

public partial class FrmFunctioncs : System.Web.UI.Page
{
    SqlCommand cmd ;
    SqlDataReader dr;

    protected void Button1_Click(object sender, EventArgs e)
    {
        SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
        string query = "SELECT * FROM dbo.whichContinent('France')";
        cmd=new SqlCommand (query ,conn ) ;
        conn.Open();
        dr = cmd.ExecuteReader();  
       string continentName = dr["Continent"].ToString ();
        conn.Close ();
    }