C # obtain the week start time/Month start time/year start time of the specified time

Datetime. Now = 2009-7-16 5:20:56

// Today

Datetime. Now. Date. tostring ();
"2009-7-16 0:00:00"

// Week start date

Datetime. Now. Date. adddays (-(INT) (datetime. Now. dayofweek) + 1). tostring ();
{0:00:00}
Datetime. Now. Date. adddays (7-(INT) (datetime. Now. dayofweek). tostring ();
{0:00:00}

// Start date of the month
New datetime (datetime. Now. Year, datetime. Now. month, 1). tostring ();
{0:00:00}

New datetime (datetime. now. date. year, datetime. now. date. month, datetime. daysinmonth (datetime. now. date. year, datetime. now. date. month )). tostring ();
"0:00:00"

// Start date of the year
New datetime (datetime. Now. Date. Year, 1, 1). tostring ();
{0:00:00}
New datetime (datetime. Now. Date. year, 12, datetime. daysinmonth (datetime. Now. Date. Year, datetime. Now. Date. month). tostring ();
{0:00:00}