public static System.int DayOfWeek( 
   System.DateTime datetime
)

Parameters

datetime

Date of the System.DateTime type.

Return Value

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference