use dateonly value as below
foreach (var cstatus in DMStatusReports_D.DM_CI_STATUS.Where(cs => cs.WorkedOn == dateonly ))
{
}
depending on the data type you can set the value of dateonly field as below
if your database WorkedOn is varchar then use
string dateonly = DateTime.Now.AddDays(-1).ToString("yyyy-MM-dd");
if your database WorkedOn is a Date column then
DateTime dateonly = DateTime.Now.Date;