Creating a functional Double Control - wpf

Question

I have a custom control called DoubleNumericBox that validates and accepts user input like 23,00, 0,9, 23.900,01, 34... etc.
The problem starts when I try to binding something to it. The binding is not reliable enough, some times the control won't display the new value, but if I set the DataContext one more time it will set the value, etc.
So, I must be doing something very wrong with my custom properties and events.
Custom Properties/Events
Value : Double
MinValue : Double
MaxValue : Double
ValueChanged : Event
Expected Behaviour
Validate typed keys: Numbers, Commas and Points (Decimal separator and digit grouping glyph). My culture uses Comma as decimal separator.
Validate the whole text if (return to the latest Value if number not valid):
Text pasted.
Lost Focus.
Validate Min/Max limit.
Accept binding from Text or Value, and validate the binding value.
Code
public class DoubleNumericBox : TextBox
{
Variables:
public readonly static DependencyProperty MinValueProperty;
public readonly static DependencyProperty ValueProperty;
public readonly static DependencyProperty MaxValueProperty;
Properties:
public double MinValue
{
get { return (double)GetValue(MinValueProperty); }
set { SetCurrentValue(MinValueProperty, value); }
}
public double Value
{
get { return (double)GetValue(ValueProperty); }
set
{
SetCurrentValue(ValueProperty, value);
RaiseValueChangedEvent();
}
}
public double MaxValue
{
get { return (double)GetValue(MaxValueProperty); }
set { SetCurrentValue(MaxValueProperty, value); }
}
Event:
public static readonly RoutedEvent ValueChangedEvent;
public event RoutedEventHandler ValueChanged
{
//Provide CLR accessors for the event
add { AddHandler(ValueChangedEvent, value); }
remove { RemoveHandler(ValueChangedEvent, value); }
}
public void RaiseValueChangedEvent()
{
var newEventArgs = new RoutedEventArgs(ValueChangedEvent);
RaiseEvent(newEventArgs);
}
Constructor/Override:
static DoubleNumericBox()
{
MinValueProperty = DependencyProperty.Register("MinValue", typeof(double), typeof(DoubleNumericBox), new FrameworkPropertyMetadata(0D));
ValueProperty = DependencyProperty.Register("Value", typeof(double), typeof(DoubleNumericBox), new FrameworkPropertyMetadata(0D, ValueCallback));
MaxValueProperty = DependencyProperty.Register("MaxValue", typeof(double), typeof(DoubleNumericBox), new FrameworkPropertyMetadata(Double.MaxValue));
ValueChangedEvent = EventManager.RegisterRoutedEvent("ValueChanged", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(DoubleNumericBox));
}
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
PreviewTextInput += DoubleNumericBox_PreviewTextInput;
ValueChanged += DoubleNumericBox_ValueChanged;
TextChanged += DoubleNumericBox_TextChanged;
LostFocus += DoubleNumericBox_LostFocus;
AddHandler(DataObject.PastingEvent, new DataObjectPastingEventHandler(PastingEvent));
}
Events:
private static void ValueCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var textBox = d as DoubleNumericBox;
if (textBox == null) return;
//textBox.Text = String.Format("{0:###,###,##0.0###}", textBox.Value);
textBox.RaiseValueChangedEvent();
}
private void DoubleNumericBox_ValueChanged(object sender, RoutedEventArgs e)
{
var textBox = sender as DoubleNumericBox;
if (textBox == null) return;
ValueChanged -= DoubleNumericBox_ValueChanged;
TextChanged -= DoubleNumericBox_TextChanged;
if (Value > MaxValue)
Value = MaxValue;
else if (Value < MinValue)
Value = MinValue;
textBox.Text = Text = String.Format("{0:###,###,##0.0###}", Value);
ValueChanged += DoubleNumericBox_ValueChanged;
TextChanged += DoubleNumericBox_TextChanged;
}
private void DoubleNumericBox_TextChanged(object sender, TextChangedEventArgs e)
{
var textBox = sender as TextBox;
if (textBox == null) return;
if (String.IsNullOrEmpty(textBox.Text)) return;
if (IsTextDisallowed(textBox.Text)) return;
ValueChanged -= DoubleNumericBox_ValueChanged;
var newValue = Convert.ToDouble(textBox.Text);
if (newValue > MaxValue)
Value = MaxValue;
else if (newValue < MinValue)
Value = MinValue;
else
{
Value = newValue;
}
ValueChanged += DoubleNumericBox_ValueChanged;
}
private void DoubleNumericBox_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
if (String.IsNullOrEmpty(e.Text))
{
e.Handled = true;
return;
}
//Only Numbers, comma and points.
if (IsEntryDisallowed(sender, e.Text))
{
e.Handled = true;
}
}
private void PastingEvent(object sender, DataObjectPastingEventArgs e)
{
if (e.DataObject.GetDataPresent(typeof(String)))
{
var text = (String)e.DataObject.GetData(typeof(String));
if (IsTextDisallowed(text))
{
e.CancelCommand();
}
}
else
{
e.CancelCommand();
}
}
private void DoubleNumericBox_LostFocus(object sender, RoutedEventArgs e)
{
TextChanged -= DoubleNumericBox_TextChanged;
Text = String.Format("{0:###,###,##0.0###}", Value);
TextChanged += DoubleNumericBox_TextChanged;
}
Methods:
private bool IsEntryDisallowed(object sender, string text)
{
var regex = new Regex(#"^[0-9]|\.|\,$");
if (regex.IsMatch(text))
{
return !CheckPontuation(sender, text);
}
//Not a number or a Comma/Point.
return true;
}
private bool IsTextDisallowed(string text)
{
var regex = new Regex(#"^((\d+)|(\d{1,3}(\.\d{3})+)|(\d{1,3}(\.\d{3})(\,\d{3})+))((\,\d{4})|(\,\d{3})|(\,\d{2})|(\,\d{1})|(\,))?$");
return !regex.IsMatch(text); //\d+(?:,\d{1,2})?
}
private bool CheckPontuation(object sender, string next)
{
var textBox = sender as TextBox;
if (textBox == null) return true;
if (Char.IsNumber(next.ToCharArray()[0]))
return true;
if (next.Equals("."))
{
var textAux = textBox.Text;
if (!String.IsNullOrEmpty(textBox.SelectedText))
textAux = textAux.Replace(textBox.SelectedText, "");
//Check if the user can add a point mark here.
var before = textAux.Substring(0, textBox.SelectionStart);
var after = textAux.Substring(textBox.SelectionStart);
//If no text, return true.
if (String.IsNullOrEmpty(before) && String.IsNullOrEmpty(after)) return true;
if (!String.IsNullOrEmpty(before))
{
if (before.Contains(',')) return false;
if (after.Contains("."))
{
var split = before.Split('.');
if (split.Last().Length != 3) return false;
}
}
if (!String.IsNullOrEmpty(after))
{
var split = after.Split('.', ',');
if (split.First().Length != 3) return false;
}
return true;
}
//Only one comma.
if (next.Equals(","))
{
return !textBox.Text.Any(x => x.Equals(','));
}
return true;
}
}
Can you guys help me out to make this custom control work better?

Answer 1

So a couple of gotchas I see in your code:
Do not use += / -= to hook up events in WPF controls, it can and will break routed events, use Addhandler / RemoveHandler instead.
I removed the unhooking and rehooking of events and used a member level flag instead for change loop issues. Here is the code I came up with, seem to bind fine to Value field.
A side note, you failed to account for multiple "." entry in your textbox so a user could type 345.34.434.23 which would not be prevented. I know to check this because I wrote a WPF FilterTextBox years ago and this came up in my testing.
public class DoubleNumericBox : TextBox
{
public readonly static DependencyProperty MinValueProperty;
public readonly static DependencyProperty ValueProperty;
public readonly static DependencyProperty MaxValueProperty;
public bool _bIgnoreChange = false;
public double MinValue
{
get { return (double)GetValue(MinValueProperty); }
set { SetCurrentValue(MinValueProperty, value); }
}
public double Value
{
get { return (double)GetValue(ValueProperty); }
set
{
SetCurrentValue(ValueProperty, value);
RaiseValueChangedEvent();
}
}
public double MaxValue
{
get { return (double)GetValue(MaxValueProperty); }
set { SetCurrentValue(MaxValueProperty, value); }
}
public static readonly RoutedEvent ValueChangedEvent;
public event RoutedEventHandler ValueChanged
{
//Provide CLR accessors for the event
add { AddHandler(ValueChangedEvent, value); }
remove { RemoveHandler(ValueChangedEvent, value); }
}
public void RaiseValueChangedEvent()
{
var newEventArgs = new RoutedEventArgs(ValueChangedEvent);
RaiseEvent(newEventArgs);
}
static DoubleNumericBox()
{
MinValueProperty = DependencyProperty.Register("MinValue", typeof(double), typeof(DoubleNumericBox), new FrameworkPropertyMetadata(0D));
ValueProperty = DependencyProperty.Register("Value", typeof(double), typeof(DoubleNumericBox), new FrameworkPropertyMetadata(0D, ValueCallback));
MaxValueProperty = DependencyProperty.Register("MaxValue", typeof(double), typeof(DoubleNumericBox), new FrameworkPropertyMetadata(Double.MaxValue));
ValueChangedEvent = EventManager.RegisterRoutedEvent("ValueChanged", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(DoubleNumericBox));
}
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
AddHandler(TextBox.PreviewTextInputEvent, new TextCompositionEventHandler(DoubleNumericBox_PreviewTextInput));
AddHandler(TextBox.TextChangedEvent, new TextChangedEventHandler(DoubleNumericBox_TextChanged));
AddHandler(TextBox.LostFocusEvent, new RoutedEventHandler(DoubleNumericBox_LostFocus));
AddHandler(DataObject.PastingEvent, new DataObjectPastingEventHandler(PastingEvent));
}
private static void ValueCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var textBox = d as DoubleNumericBox;
if (textBox == null) return;
//textBox.Text = String.Format("{0:###,###,##0.0###}", textBox.Value);
textBox.DoubleNumericBox_ValueChanged();
}
private void DoubleNumericBox_ValueChanged()
{
if (Value > MaxValue)
Value = MaxValue;
else if (Value < MinValue)
Value = MinValue;
if (!_bIgnoreChange)
this.Text = Text = String.Format("{0:###,###,##0.0###}", Value);
}
private void DoubleNumericBox_TextChanged(object sender, TextChangedEventArgs e)
{
var textBox = sender as TextBox;
if (textBox == null) return;
if (String.IsNullOrEmpty(textBox.Text)) return;
if (IsTextDisallowed(textBox.Text)) return;
//ValueChanged -= DoubleNumericBox_ValueChanged;
_bIgnoreChange = true;
Value = Convert.ToDouble(textBox.Text);
//if (newValue > MaxValue)
// Value = MaxValue;
//else if (newValue < MinValue)
// Value = MinValue;
//else
//{
// Value = newValue;
//}
_bIgnoreChange = false;
//ValueChanged += DoubleNumericBox_ValueChanged;
}
private void DoubleNumericBox_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
if (String.IsNullOrEmpty(e.Text))
{
e.Handled = true;
return;
}
//Only Numbers, comma and points.
if (IsEntryDisallowed(sender, e.Text))
{
e.Handled = true;
}
}
private void PastingEvent(object sender, DataObjectPastingEventArgs e)
{
if (e.DataObject.GetDataPresent(typeof(String)))
{
var text = (String)e.DataObject.GetData(typeof(String));
if (IsTextDisallowed(text))
{
e.CancelCommand();
}
}
else
{
e.CancelCommand();
}
}
private void DoubleNumericBox_LostFocus(object sender, RoutedEventArgs e)
{
//TextChanged -= DoubleNumericBox_TextChanged;
Text = String.Format("{0:###,###,##0.0###}", Value);
//TextChanged += DoubleNumericBox_TextChanged;
}
private bool IsEntryDisallowed(object sender, string text)
{
var regex = new Regex(#"^[0-9]|\.|\,$");
if (regex.IsMatch(text))
{
return !CheckPontuation(sender, text);
}
//Not a number or a Comma/Point.
return true;
}
private bool IsTextDisallowed(string text)
{
var regex = new Regex(#"^((\d+)|(\d{1,3}(\.\d{3})+)|(\d{1,3}(\.\d{3})(\,\d{3})+))((\,\d{4})|(\,\d{3})|(\,\d{2})|(\,\d{1})|(\,))?$");
return !regex.IsMatch(text); //\d+(?:,\d{1,2})?
}
private bool CheckPontuation(object sender, string next)
{
var textBox = sender as TextBox;
if (textBox == null) return true;
if (Char.IsNumber(next.ToCharArray()[0]))
return true;
if (next.Equals("."))
{
var textAux = textBox.Text;
if (!String.IsNullOrEmpty(textBox.SelectedText))
textAux = textAux.Replace(textBox.SelectedText, "");
//Check if the user can add a point mark here.
var before = textAux.Substring(0, textBox.SelectionStart);
var after = textAux.Substring(textBox.SelectionStart);
//If no text, return true.
if (String.IsNullOrEmpty(before) && String.IsNullOrEmpty(after)) return true;
if (!String.IsNullOrEmpty(before))
{
if (before.Contains(',')) return false;
if (after.Contains("."))
{
var split = before.Split('.');
if (split.Last().Length != 3) return false;
}
}
if (!String.IsNullOrEmpty(after))
{
var split = after.Split('.', ',');
if (split.First().Length != 3) return false;
}
return true;
}
//Only one comma.
if (next.Equals(","))
{
return !textBox.Text.Any(x => x.Equals(','));
}
return true;
}
}