CODEWITHSUNDEEP
c#wpfxamlmvvmdatepicker
Denis Krasakov
Denis Krasakov

Reputation: 1578

WPF Datepicker text isn`t changed according to binding when user clear date

I have datepicker on my window and want to achieve simple behaviour: when user clear datepicker's text set datepicker date to Today

XAML:

<DatePicker SelectedDate="{Binding DateFrom}" Width="150" Margin="0,20,0,0"></DatePicker>

ViewModel DateFrom property:

public DateTime? DateFrom
{
  get { return dateFrom; }
  set
  {
    if (dateFrom == value) return;
    dateFrom = value ?? DateTime.Today;
    OnPropertyChanged();
   }
}

But I encounter weird behaviour if user clear today date from datepicker - on UI datepicker stays empty, but in ViewModel I have DateFrom == DateTime.Today. If user clear any other date all works as expected, only scenario with Today Date fails.

Is this datepicker issue or I'm missing something?

Upvotes: 3

Views: 2018

Answers (2)

user7816380
user7816380

Reputation:

That should do the trick.

<DatePicker SelectedDate="{Binding DateFrom, UpdateSourceTrigger=LostFocus}"
  Width="150" Margin="0,20,0,0"></DatePicker>

The value of UpdateSourceTrigger is PropertyChanged by default. But when you clear today's date, the property is not changing.

So, you have to change the value of UpdateSourceTrigger to LostFocus. In that case the property is updated every time DatePicker loses focus.

Upvotes: 1

icebat
icebat

Reputation: 4774

Internally it checks previous and current values, and raises property changed only if they are different. I suppose it's pickerAutomationPeer.RaiseValuePropertyChangedEvent(oldValue, newValue); if you dig into OnSelectedDateChanged code inside DatePicker.

The easiest way to avoid that is to make values always different by using DateTime.Now instead of DateTime.Today.

Upvotes: 1

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