No available TextChanged event

Hi

I am using a CurrencyTextBox control.  The problem that I am having is that I do not see a TextChanged event.  I would like to be able to do a validation on the data being entered.  I tried using "TextUpdated" but that does not work.

                    <ms:CurrencyTextBox Grid.Column="1" Grid.Row="8" Name="mTxtSellPrice"
                        Culture="{Binding SelectedValue, ElementName=CultureBox, Converter={StaticResource DefaultCultureIfNull}}"
                        LostFocus="mTxtSellPrice_LostFocus"
                        Margin="3"
                        Background="White"
                        Padding="1"
                        BorderThickness="2"
                        BorderBrush="Transparent"
                        ToolTip="Tool Tip Missing">
                     </ms:CurrencyTextBox>

What event should I use for Text being changed or is there an example that I can look at.

Thanks

Hi

I am using a CurrencyTextBox control.  The problem that I am having is that I do not see a TextChanged event.  I would like to be able to do a validation on the data being entered.  I tried using "TextUpdated" but that does not work.

 <ms:CurrencyTextBox Grid.Column="1" Grid.Row="8" Name="mTxtSellPrice"
                        Culture="{Binding SelectedValue, ElementName=CultureBox, Converter={StaticResource DefaultCultureIfNull}}"
         LostFocus="mTxtSellPrice_LostFocus"
         Margin="3"
         Background="White"
         Padding="1"
         BorderThickness="2"
         BorderBrush="Transparent"
         ToolTip="Tool Tip Missing">
 </ms:CurrencyTextBox>

Here I am using a standard TextBox to handle validation and using a TextChanged how can I do this with a CurrencyTextBox and also handle validation.

  <TextBox Style="{StaticResource textBoxInError}" Grid.Column="1" Grid.ColumnSpan="1" Grid.Row="7" VerticalAlignment="Center" Name="mTxtQuantity" Margin="3" TextChanged="mTxtQuantity_TextChanged" TabIndex="6">
   <!-- Setting the ValidatesOnDataErrors to true enables to the Binding to check for
                       errors raised by the IDataErrorInfo implementation. -->
     <TextBox.Text>
           <Binding Path="Quantity"
               Mode="TwoWay"
               ValidatesOnDataErrors="True"  
               UpdateSourceTrigger="PropertyChanged">
              <Binding.Converter>
                   <helperClass:IntegerConverter></helperClass:IntegerConverter>
              </Binding.Converter>
                                                                  
              <Binding.ValidationRules>
              <!-- Checks for exceptions during the setting of the source property. -->
                   <helperClass:IntegerlValidationRule/>
              </Binding.ValidationRules>
           </Binding>
     </TextBox.Text>
  </TextBox>
 

What event should I use for Text being changed and is there an example that I can look at.

You can catch the bubbling TextBox.TextChanged event from the contained TextBox:

<ms:CurrencyTextBox Value="123" TextBoxBase.TextChanged="CurrencyTextBox_TextChanged" />

You should be able to data bind (including validations) the Text property in the same way as for a TextBox but you might want to consider binding the Value property rather than the Text property. 

Great !

Thanks I will give this a try.

Hi Ivan,

Is it possible to provide an example on using the validation from my example.  I am not having any luck getting this to work.

Sure.  First, let's create a simple business object.  You've obviously already got one of these, but I wanted to write my demo example out so as to make sure we're both on the same page.

  public class Sprocket : INotifyPropertyChanged, IDataErrorInfo
  {
    private decimal _price;

    public decimal Price
    {
      get { return _price; }
      set { Set(ref _price, value, "Price"); }
    }

    public string Error
    {
      get { return GetPriceErrorString(); }
    }

    public string this[string columnName]
    {
      get
      {
        if (columnName == "Price")
        {
          return GetPriceErrorString();
        }
        return null;
      }
    }

    private string GetPriceErrorString()
    {
      return Price > 500 ? "Quel horreur" : null;
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
      if (PropertyChanged != null)
      {
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
      }
    }

    private void Set<T>(ref T field, T value, string propertyName)
    {
      if (!Object.Equals(field, value))
      {
        field = value;
        OnPropertyChanged(propertyName);
      }
    }
  }

A fair chunk of this is INotifyPropertyChanged boilerplate.  The IDataErrorInfo implementation is barbarous but it will do for demo purposes.

We set the window data context to a Sprocket instance:

DataContext = new Sprocket { Price = 246 }; 

Now let's create a validation rule, say a range constraint:

  public class RangeRule : ValidationRule
  {
    public decimal Minimum { get; set; }
    public decimal Maximum { get; set; }

    public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo)
    {
      decimal d = Convert.ToDecimal(value, cultureInfo);
      bool isValid = (d >= Minimum && d <= Maximum);
      return new ValidationResult(isValid, "Oh noes!");  // better error message required
    }
  }

Again, you've clearly already got one of these.

Finally, we create a CurrencyTextBox and hook up its TextBoxBase.TextChanged event and bind its Value with validation.  This is similar to your example except that I am binding the Value property rather than the Text property, since Value is more appropriate to a numeric data property like Price or Quantity:

    <ms:CurrencyTextBox TextBoxBase.TextChanged="CurrencyTextBox_TextChanged">
      <ms:CurrencyTextBox.Value>
        <Binding Path="Price" ValidatesOnDataErrors="True" UpdateSourceTrigger="PropertyChanged">
          <Binding.ValidationRules>
            <local:RangeRule Minimum="0" Maximum="1000" />
          </Binding.ValidationRules>
        </Binding>
      </ms:CurrencyTextBox.Value>
    </ms:CurrencyTextBox>

Now when I type into the CurrencyTextBox, I see the TextChanged handler running (printing output to the debug window in my case).  Also, if I type a value greater than 500, the CurrencyTextBox gets a red border. (If I remove the ValidatesOnDataErrors setting and type a value greater than 1000, the CurrencyTextBox gets a red border, so I know the RangeRule is being applied as well as IDataErrorInfo.)

Hope this helps! 

Thanks Ivan,

Good example !

Hi Ivan,

I was able to get the example that you sent to work.  My only problem now is how can I get the DropDownDatePicker to remove the calendar and just show the date selected after loosing focus without having the user click on the arrow.

Hmm, this feels like a bit of a bug.  However, you can work around it as follows:

1. Add a PreviewKeyDown handler to the control, and set its KeyboardNavigation.TabNavigation attached property to None:

<ms:DropDownDatePicker KeyboardNavigation.TabNavigation="None" PreviewKeyDown="DropDownDatePicker_PreviewKeyDown" />

2. In the PreviewKeyDown handler, close the drop-down and handle the tabbing manually:

private void DropDownDatePicker_PreviewKeyDown(object sender, KeyEventArgs e)
{
  if (e.Key == Key.Tab)
  {
    DropDownDatePicker dddp = (DropDownDatePicker)sender;

    DropDownEditBox ddeb = FindChild<DropDownEditBox>(dddp);
    ddeb.IsDropDownOpen = false;

    dddp.Focus();
    dddp.MoveFocus(new TraversalRequest(FocusNavigationDirection.Next));

    e.Handled = true;
  }
}

3. The implementation of FindChild looks like this:

private static T FindChild<T>(DependencyObject startingFrom)
  where T : class
{
  for (int i = 0; i < VisualTreeHelper.GetChildrenCount(startingFrom); ++i)
  {
    DependencyObject child = VisualTreeHelper.GetChild(startingFrom, i);
    T instance = child as T;
    if (instance != null)
    {
      return instance;
    }
    instance = FindChild<T>(child);
    if (instance != null)
    {
      return instance;
    }
  }
  return null;
}

I know this is ugly but hopefully it will be okay until we are able to improve the built-in tab handling.