Question

I have the following definition for a DatePicker:

<sdk:DatePicker x:Name="dtpStartDate"
                Grid.Row="4"
                Grid.Column="1"
                SelectedDateFormat="Short"
                SelectedDate="{Binding MyObject.StartDate, Mode=TwoWay, NotifyOnValidationError=True}"/>

MyObject is a class that contains the StartDate which is defined as a nullable DateTime.

class MyObjectClass
{
    ....
    public DateTime? StartDate { get; set; }
    ....
}

I’m using MVVM (via Prism) and MyObject is correctly bound.

The first time I display this view the date is blank (as expected) and when I click on the picker the calendar is displayed with today’s date highlighted.

If I select a date (other than today) or display a record with a date filled then when I blank the form to create a new object:

this.MyObject = new MyObjectClass();

the date hightlighted when I click on the picker is the previously selected date.

So if the record showed “1st May 2009” that’s what would be highlighted in the picker. I can set StartDate to DateTime.Today which is correctly displayed, but does mean that a date is displayed in the form which I don’t want.

So, why doesn’t setting the date to null reset the selected date in the picker to today?

Answer 1

The solution is to reset the DisplayDate property on the DatePicker:

        this.SelectedDateChanged += (s, e) =>
        {
            if (this.SelectedDate == null)
            {
                this.DisplayDate = DateTime.Today;
                this.Text = string.Empty;
            }
        };

To add this functionality we had to subclass the DataPicker though.