datetime

urgent help...
hei..
sample scenario..
i have a task which is divided into subtask. if there is 2 subtask first subtask starting date is 1 oct 2012 and subtask starting date is 3 oct 2012 i want to make the starting date of the task 1 oct 2012...
here is my code..
var w = from a in en2.sub_tasks
where a.project_id == projectids
&& a.taskid == taskids
&& a.subtask_name == TextBox1.Text
select a;
if (w.Count()> 0)
{
foreach (var u in w)
{
DateTime startdate = Convert.ToDateTime(u.startDate);

DateTime enddate = Convert.ToDateTime(u.endDate);
now what... ??
}
table name is task and column name is startingdate..

...