set nocount on
declare @dt datetime,
@from datetime, 
@to datetime, 
@Day_to_get varchar(20)
set @from = (Select StartDate from [Class] where ID = 123)
set @to = (Select FinishDate from [Class] where ID = 123)
set @Day_to_get = 'Friday' 
declare @dates table ([dates] datetime)
Select @dt =
case
when datename(weekday,@from) = @Day_to_get then @from
when datename(weekday,dateAdd(day,1,@from)) = @Day_to_get then dateAdd(day, 1, @from)
when datename(weekday,dateAdd(day,2,@from)) = @Day_to_get then dateAdd(day, 2, @from)
when datename(weekday,dateAdd(day,3,@from)) = @Day_to_get then dateAdd(day, 3, @from)
when datename(weekday,dateAdd(day,4,@from)) = @Day_to_get then dateAdd(day, 4, @from)
when datename(weekday,dateAdd(day,5,@from)) = @Day_to_get then dateAdd(day, 5, @from)
when datename(weekday,dateAdd(day,6,@from)) = @Day_to_get then dateAdd(day, 6, @from)
 end  
While @dt <= @to
Begin
 insert @dates values (@dt)
 Select @dt = dateadd(day,7,@dt)
End
Select * from @dates

CREATE TABLE dbo.Times 
(
ClassID INT, 
DayID TINYINT
)

SELECT 
	c.ClassID, 
	DATEADD(day, n.number, c.startdate)
FROM Class AS c
	join Numbers AS n
		ON n.number <= DATEDIFF(day, c.startdate, c.FinishDate)
		JOIN Times AS t
			ON t.dayid = DATEPART(weekday, DATEADD(day, n.number, c.startdate))
WHERE 
	c.ClassID = @ClassID