how to get Number of days of current Month in sql server?

CREATE FUNCTION [dbo].[ufn_GetDaysInMonth] ( @pDate    DATETIME ) RETURNS INT AS BEGIN      RETURN CASE WHEN MONTH(@pDate) IN (1, 3, 5, 7, 8, 10, 12) THEN 31                 WHEN MONTH(@pDate) IN (4, 6, 9, 11) THEN 30                 ELSE CASE WHEN (YEAR(@pDate) % 4    = 0 AND                                 YEAR(@pDate) % 100 != 0) OR                                (YEAR(@pDate) % 400  = 0)                           THEN 29                           ELSE 28                      END            END  END GO