XAML ReadOnly ComboBox - wpf

Question

To set up a ReadOnly ComboBox in XAML (WPF), you have to set up a ComboBox and a TextBox showing only one of them according to a pair of properties IsReadOnly/IsEditable that must exist on your ViewModel. Note that on this sample "UserNVL" must exist in the resources and it should be a NameValueList collection that allows us to convert ID to names. In this case the RecipientID is the key for a user name. Note also the VisibilityConverter must also exist in the resources and it's a standard BooleanToVisibilityConverter.
Gosh! This was so hard to find I had to made it myself. This allows the user the select the content of the text box. No way a disabled ComboBox would ever allow you to do it.

Answer 1

There are two properties named IsHitTestVisible & IsTabVisible. the former makes the control deaf to mouse events and the latter to keyboard events.
This could help you as it would not give the disabled look to your combo box but you will succeed in making a read only combo box..
Source :-
http://www.telerik.com/community/forums/wpf/combobox/isreadonly-does-seem-to-work.aspx

Answer 2

Why not just set IsEnabled=false?

Answer 3

<DockPanel>
<TextBlock Text="Recipient" Margin="6,9,3,6" HorizontalAlignment="Right"/>
<ComboBox
x:Name="RecipientID"
ItemsSource="{Binding Source={StaticResource UserNVL}}"
DisplayMemberPath="Value"
SelectedValuePath="Key"
SelectedValue="{Binding Path=RecipientID}"
Height="20"
Margin="6,6,0,6"
MinWidth="200"
HorizontalAlignment="Left"
IsEditable ="True"
Visibility="{Binding Path=IsEditable, Converter={StaticResource VisibilityConverter}}"/>
<TextBox
x:Name="RecipientName"
Text="{Binding ElementName=RecipientID, Path=Text}"
Margin="6,6,0,6"
MinWidth="200"
HorizontalAlignment="Left"
Style="{StaticResource textBoxInError}"
Visibility="{Binding Path=IsReadOnly, Converter={StaticResource VisibilityConverter}}"/>
</DockPanel>

Answer 4

I think that you will find it much easier and practical to create a class to extend the ComboBox class in this very simple manner:
override the OnSelectionChanged method of the Combobox to check the property IsReadOnly before to allow base.OnSelectionChanged(e) to run.
That way you just have to set ComboBox.IsReadOnly property to True. No big XAML to write everywhere...

Answer 5

Here is a custom ComboBox subclass that gives the read only behaviour I needed for my scenario:
public class ReadOnlyComboBox : ComboBox
{
static ReadOnlyComboBox()
{
IsDropDownOpenProperty.OverrideMetadata(typeof(ReadOnlyComboBox), new FrameworkPropertyMetadata(
propertyChangedCallback: delegate { },
coerceValueCallback: (d, value) =>
{
if (((ReadOnlyComboBox)d).IsReadOnly)
{
// Prohibit opening the drop down when read only.
return false;
}
return value;
}));
IsReadOnlyProperty.OverrideMetadata(typeof(ReadOnlyComboBox), new FrameworkPropertyMetadata(
propertyChangedCallback: (d, e) =>
{
// When setting "read only" to false, close the drop down.
if (e.NewValue is true)
{
((ReadOnlyComboBox)d).IsDropDownOpen = false;
}
}));
}
protected override void OnSelectionChanged(SelectionChangedEventArgs e)
{
if (IsReadOnly)
{
// Disallow changing the selection when read only.
e.Handled = true;
return;
}
base.OnSelectionChanged(e);
}
}
Points about this approach:
Doesn't break any existing styles applied to the element, unlike an approach that introduces additional UI elements.
Doesn't break input focus while read only. You can still tab into and click to focus this element. This is more accessible, which is a concern in my scenario.
The UI element doesn't, but default, look any different when read only. If you need that, you would have to apply relevant styles to make it so.

Answer 6

If IsEnabled is set to false, Combobox value is nearly not readable. What I found as suitable solution is:
combobox and textbox (formated as readonly) are in the same grid position
combobox spans to next column to gain additional 15 width so dropdown button is visible
textbox.IsVisible is bound to combobox.IsEnabled with bool to visibility converter.
textbox.Text is bound to combobox.SelectedItem (in my case it is strongly typed so I actually bound into .DisplayText of it)