Apply Case statement in Where clause in SSMS

Here i will explain, how can we apply Case statement in Where clause.
Look on the example given below.

I am having a Table called DIM_DATE.
This table contain 4 column (DATE, MONTH_OF_YEAR ,WEEK_OF_YEAR,YEAR)

Now look on the below query :-

DECLARE  @Rpt_Parm_Is_Week BIT

        ,@Rpt_Parm_Month INT

        ,@Rpt_Parm_Week INT

           

SELECT DATE,MONTH_OF_YEAR ,WEEK_OF_YEAR,YEAR FROM DIM_DATE

 WHERE YEAR=2015

           

 AND MONTH_OF_YEAR = CASE WHEN @Rpt_Parm_Is_Week = 1 THEN  MONTH_OF_YEAR ELSE @Rpt_Parm_Month  END

           

 AND WEEK_OF_YEAR =  CASE WHEN @Rpt_Parm_Is_Week = 0 THEN WEEK_OF_YEAR ELSE @Rpt_Parm_Week END    

Now   will pass some value into those parameter.

 @Rpt_Parm_Is_Week = 1

 @Rpt_Parm_Month = 5

 @Rpt_Parm_Week=21

 Output: Will get only one week(21) value for particular month(5) in 2015 year.

Now   will pass fasle value into @Rpt_Parm_Is_Week parameter.

 @Rpt_Parm_Is_Week = 0

 @Rpt_Parm_Month = 5

 @Rpt_Parm_Week=21

Output: Will get whole one month(5) record for 2015 year.