title: Update Date Picker Value on LOST FOCUS
body: <p>I have a custom date picker in wpf below is the code of <strong>xaml</strong></p>
  
  <pre><code>&lt;local:Customdatepicker x:Uid="dateValue" 
      x:Name="dateValue" 
      BorderThickness="0" 
      Visibility="{Binding ShowDatePicker, UpdateSourceTrigger=PropertyChanged}" 
      IsEnabled="{Binding FieldValueIsEditable, UpdateSourceTrigger=PropertyChanged}"                                                DateCoordinates="{Binding CoOrdinates, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"
      Text="{Binding DateFieldValue, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True, TargetNullValue=''}"   
      Loaded="dateValue_Loaded" 
      Style="{StaticResource DatePickerStyle}" 
      Width="{Binding DatePickerWidth, UpdateSourceTrigger=PropertyChanged}"                                                MouseDoubleClick="dateValue_MouseDoubleClick"  
      DisplayDate="{Binding DisplayDateFieldValue, Mode=TwoWay}"
      LostFocus="dateValue_LostFocus" /&gt;
  </code></pre>
  
  <p><strong>class</strong></p>
  
  <pre><code>public class Customdatepicker : DatePicker {
      public Customdatepicker() {
          DefaultStyleKey = typeof(DatePicker);
      }
  
      public _Coordinates DateCoordinates {
            get { return (_Coordinates) GetValue(CoordinatesProperty); }
            set { SetValue(CoordinatesProperty, value); }
      }
  
      public static readonly DependencyProperty CoordinatesProperty =
          DependencyProperty.Register("DateCoordinates", typeof(_Coordinates), typeof(Customdatepicker), null);
  }
  </code></pre>
  
  <p>I want to validate date on <strong>Lost focus</strong> if I entered wrong date I want to update it but I'm unable to do so. Please let me know how I can do it on LOST FOCUS.</p>