如何使用C＃在ASP MVC中的下拉列表中创建唯一的日期列表？

Question

I'm working with the Entity framework in ASP MVC and I want to pull a list of unique dates from the database that has a datetime field and display them in a drop down. I can't find a way to format the output and only list the unique dates in order so whomever is on the page will see something like "8/7/2015", "8/8/2015" instead of "8/7/2015 11:00:00 AM" and "8/7/2015 11:25:00 AM"... for AppointmentStartDateTime .

Here's my Model so far

public class Appointment
{
    [Key]
    [Column("apt_Id")]
    [Display(Name = "Appointment Id")]
    public int AppointmentId { get; set; }

    [Column("apt_apl_Id")]
    public int AppealId { get; set; }
    public virtual Appeal Appeal { get; set; }

    [Column("apt_ofh_Id")]
    public int OfficeHoursId { get; set; }
    public virtual OfficeHours OfficeHours { get; set; }

    [Column("apt_StartDateTime")]
    public DateTime AppointmentStartDateTime { get; set; }
    [Column("apt_EndDateTime")]
    public DateTime AppointmentEndDateTime { get; set; }
}

I'm stuck in the controller in the code shown below:

SelectList AppointmentDateSelectList = new SelectList(
    db.Appointment.Where(g => g.AppointmentStartDateTime > DateTime.Now),
    "AppointmentStartDateTime","AppointmentStartDateTime")
    .Select(a => new SelectListItem
    {
        Text = Convert.ToDateTime(a.Text).ToShortDateString(),
        Value = a.Value
    });

I'm hoping someone knows how to make unique date list out of the start times. I haven't found any information on it and I feel like I'm banging my head against a wall.

Answer 1

Instead of using ToShortDateString() , use ToString("MM/dd/yyyy") , or whatever other format you want.

NOTE: This would be a comment, but I don't have enough reputation.

Answer 2

Firstly, and a tad off-topic, but I would encourage you to use good formatting. You'd be amazed at how often weird formatting makes a piece of code seem more complicated that it is. For this reason, I would also break out the database bit into a separate variable for readability.

var matchingAppointments = db.Appointment.Where(g => g.AppointmentStartDateTime > DateTime.Now);

Secondly, I think it makes more sense to do the sorting and distinct-ifying against the database portion, not the SelectList itself:

// Renamed variable
var distinctAppointmentDates = db.Appointment.Where(appt => appt.AppointmentStartDateTime > DateTime.Now)
                                             .OrderBy(appt => appt.AppointmentStartDateTime)
                                             .ToList()  // Force query execution
                                             .Select(appt => appt.AppointmentStartDateTime.ToShortDateString())
                                             .Distinct();

SelectList AppointmentDateSelectList = new SelectList(distinctAppointmentDates);

Lastly, your use of ToShortDateString is fine so far as I can see. I'm not sure why others think that is the issue.

Answer 3

Try creating a list of selectlistitems then put that list in your selectlist

var list = db.Appointment.Where(g => g.AppointmentStartDateTime > DateTime.Now)
                         .select(s => new SelectListItem{
                                     Text = s.AppointmentStartDateTime.ToString("dd/mm/yy"), 
                                     Value = a.AppintmentStartDateTime   
                         });

var AppointmentDateSelectList  = new SelectList(list, "Text","Value");

Answer 4

To choose unique dates you can use GroupBy() in your linq query. ToString() will also help you with date format.

var list = db.Appointment.Where(g => g.AppointmentStartDateTime >DateTime.Now).GroupBy(x=>x.AppointmentStartDateTime)
    .select(s => new SelectListItem
    {
         Text = s.Key.Value.ToString("dd/mm/yy"), 
         Value = s.Key.Value.ToString()
    });

var AppointmentDateSelectList  = new SelectList(list, "Text","Value");