Different TextBox formatting in edit mode - wpf

Question

In our WPF project, we are using a TextBox to let the user enter some length measures. This measures may be in millimeters, centimeters, inches, etc (depending on the user configuration).
We need to show the numbers on the TextBox along with the current measurement unit, like:
"120 mm"
"16 cm"
"1' 2 3/4"
and so on.
I am using ValueConverter to both perform the unit converting and to add the extra formatting. The UpdateSourceTrigger is default, so the binding applies when the user leaves the control.
The challenge here is that while editing the value, these "mm" or "cm" are not shown. So the previous examples in edit mode would be:
"120"
"16"
"1 2 3/4"
How can I make that happen?
Here is the Converter code for some cenários:
/// <summary>
/// Converts and formats the value (in milimeters) to the required unit/format
/// </summary>
public class LengthConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
LengthUnit unit = MainWindow.CurrentLengthUnit;
switch (unit.Id)
{
case 1: //Milimeters
return value + " mm";
case 2: //Centimeters
return (double)value / 10.0 + " cm";
default:
throw new InvalidOperationException("Unknown length unit.");
}
}
public object ConvertBack(object value, Type targetType,
object parameter, CultureInfo culture)
{
string rawValue = value as string;
LengthUnit unit = MainWindow.CurrentLengthUnit;
switch (unit.Id)
{
case 1: //Milimeters
return rawValue.Replace("mm", "").Trim();
case 2: //Centimeters
return Double.Parse(rawValue.Replace("cm", "").Trim()) * 10.0;
default:
throw new InvalidOperationException("Unknown length unit.");
}
}
}

Answer 1

What about this:
view:
<TextBox>
<TextBox.Style>
<Style TargetType="TextBox">
<Style.Triggers>
<Trigger Property="IsFocused" Value="False">
<Setter Property="Text">
<Setter.Value>
<MultiBinding Converter="{StaticResource LengthConverter}">
<Binding Path="Foo"/>
<Binding Path="Text" RelativeSource="{RelativeSource Mode=Self}"/>
</MultiBinding>
</Setter.Value>
</Setter>
</Trigger>
<Trigger Property="IsFocused" Value="True">
<Setter Property="Text" Value="{Binding Foo}"></Setter>
</Trigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>
converter:
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
if (values.Count() > 1)
{
var value = values[1].ToString();
if (value != String.Empty)
{
int output;
Int32.TryParse(value, out output);
if (output != (int)values[0])
return value;
}
}
return String.Format("{0} {1}", values[0], "mm");
}

Answer 2

So far I managed to fix this problem using only MultiBinding and passing the TextBox control as a parameter (not very nice I suppose).
On the converter code, I check for the control property "IsFocused" and return values the way I need. I am not able to pass the "IsFocused" property directly on the binding because it is readonly while the TextBox is two way bound to the source.
The following code shows some additional handlers used to "force" binding when the controls gain or loose focus.
<TextBox x:Name="leadInTextBox"
LostFocus="SizeLostFocus"
MouseDoubleClick="SelectText"
GotKeyboardFocus="SelectText"
PreviewMouseLeftButtonDown="SelectivelyMouseButton"
PreviewTextInput="PreviewTextInput">
<TextBox.Text>
<MultiBinding Mode="TwoWay" Converter="{StaticResource MultiLengthConverter}" UpdateSourceTrigger="PropertyChanged" NotifyOnValidationError="True">
<Binding Source="{x:Static local:ApplicationService.UserInfo}" Path="LeadIn" StringFormat="F2" Mode="TwoWay" UpdateSourceTrigger="PropertyChanged"/>
<Binding RelativeSource="{RelativeSource Self}" Path="." />
</MultiBinding>
</TextBox.Text>
</TextBox>
converter:
public class MultiLengthConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
LengthUnit currentUnit = ApplicationService.UserInfo.LengthUnit;
TextBox txtBox = values[1] as TextBox;
switch (currentUnit)
{
case LengthUnit.Millimeter:
return String.Format("{0:N2}{1}", values[0], txtBox.IsFocused == true ? string.Empty : " mm");
case LengthUnit.Centimeter:
return String.Format("{0:N2}{1}", (double)values[0] / 10.0, txtBox.IsFocused == true ? string.Empty : " cm");
case LengthUnit.DecimalInch:
return String.Format("{0:N2}{1}", (double)values[0] / 25.4, txtBox.IsFocused == true ? string.Empty : " in");
default:
throw new InvalidOperationException("Unknown length unit.");
}
}
public object[] ConvertBack(object value, Type[] targetType, object parameter, CultureInfo culture)
{
string rawValue = value as string;
LengthUnit currentUnit = ApplicationService.UserInfo.LengthUnit;
object ret;
switch (currentUnit)
{
case LengthUnit.Millimeter:
ret = Double.Parse(rawValue.Replace("mm", "").Trim());
break;
case LengthUnit.Centimeter:
ret = Double.Parse(rawValue.Replace("cm", "").Trim()) * 10.0;
break;
case LengthUnit.DecimalInch:
ret = Double.Parse(rawValue.Replace("in", "").Trim()) * 25.4;
break;
default:
throw new InvalidOperationException("Unknown length unit.");
}
return new object[] { ret, null };
}
}