I have a ListBox which hold a set of objects (linked via ItemsSource bind to an ObservableCollection). I haven't used Dynamic binding yet. It currently use the ToString() method of the object. The ToString() method shows a string this way : name (someOtherProperty)
However, even if the INotifyPropertyChanged is implemented and that i use an ObservableCollection, if i change an item property this string won't be updated.
I believe that this is because it only calls ToString once. instead i guess i have to use data binding but how i can form such a string with it ? << name (someOtherProperty) >>
Thanks.
You can use a multibinding, e.g. something like this:
<MultiBinding StringFormat="{}{0} ({1})">
<Binding Path="name"/>
<Binding Path="someOtherProperty"/>
</MultiBinding>
If you just let it execute ToString there is no proper binding at all, any notifications will have no effect.
You use it like this:
<ListBox ...>
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock>
<TextBlock.Text>
<!-- The above binding here -->
</TextBlock.Text>
</TextBlock>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Related
I've got a editable combobox where I'm using an ItemTemplate that uses MultiBinding. The items displayed when the combobox is expanded display as I expect. However, when an item is selected the text displayed is the object type instead. I've seen posts that suggest overriding ToString(), but I'd like to avoid that if possible.
The object I'm bound to is a collection of UserDetail objects, among other UserDetail has a First and Last Name and an BarcodeID that I'm displaying as a string for each item in the ComboBox. I want to display that same string as the selected item. Instead what I'm seeing is MyNameSpace.UserDetail
Here's the xaml for my combobox. Please tell me where I'm going wrong:
<ComboBox IsEditable="True" IsReadOnly="False" Name="myUser"
TextBoxBase.TextChanged="myCombo_TextChanged"
SelectionChanged="myCombo_SelectionChanged">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock>
<TextBlock.Text>
<MultiBinding StringFormat="{}{1}, {0}, {2}">
<Binding Path="FirstName" />
<Binding Path="LastName" />
<Binding Path="BarcodeId" />
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
FYI, The BarcodeID is for an optional barcode badge reader.
You should only bind text data to a combobox that has IsEditable = true.
Remove IsEditable="True"
See here for more info.
Set property
TextSearch.TextPath="your_binding_property_path".
From http://www.shujaat.net/2010/08/wpf-editable-combobox-with-datatemplate.html
I have a question that is connected with setting path when binding in XAML, using WPF.
Imagine that my DataContext is of PropertyInfo type. PropertyInfo contains data about Property Name.
And in that object I nest (for example) TextBox which Text property I would like to bind to property with that name of another's element DataContext.
Something like that [it's pseudocode because it's not possible that way]:
<DataTemplate>
<TextBox Text={Binding ElementName=someElement, Path=DataContext. + {Binding Path=Name}}/>
</DataTemplate>
I want to create flexible view that's why I need to solve that problem.
Is there a way to achieve this without code behind?
Considering all the above, I think that I can make my question short and simply ask whether there is a way to concatenate string while setting binding's path.
I'm not sure if I understand correctly but is this something that multibinding would assist with?
<TextBlock Grid.Row="3" Grid.Column="1" Padding="5"><TextBlock.Text>
<MultiBinding StringFormat="[{0}, {1}]">
<Binding Path="LastName"></Binding>
<Binding Path="FirstName"></Binding>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
I have a treeview:
<TreeView>
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Path=TucActivity}">
<TextBlock>
<TextBlock.Text>
<MultiBinding StringFormat="{}{0} {1}">
<Binding Path="DisplayedStartTime"></Binding>
<Binding Path="Name"></Binding>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
<HierarchicalDataTemplate.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=Message}" />
</DataTemplate>
</HierarchicalDataTemplate.ItemTemplate>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
bounded to Observable Collection object:
MainTreeView.ItemsSource = ((App)Application.Current).TucOC;
I want that every time the ((App)Application.Current).TucOC is updated
the selected item (and also the focus) will be the one in the observable collection.
I would like to do it in one place since the ((App)Application.Current).TucOC is
updated in multiple places in the code.
What's the best option to do it?
If you're using a development pattern like MVVM, I would create a property on your ViewModel class that's of the type held in the ObservableCollection, to hold the currently selected item for your treeview source. That would look something like this:
private object _selectedTuc;
public object SelectedTuc
{
get
{
return _selectedTuc;
}
set
{
_selectedTuc = value;
OnPropertyChanged("SelectedTuc");
}
}
Then, in your treeview, you bind this property to the treeview's SelectedItem:
<TreeView ItemsSource="{Binding TucOC, Mode=OneWay}" SelectedItem="{Binding SelectedTuc, Mode=TwoWay}">...</TreeView>
Notice on the binding for SelectedItem you specify a Mode value of TwoWay - this allows for your SelectedTuc property to be updated from the UI, as well as the UI being updated whenever the SelectedTuc property changes.
If you're not using MVVM or something like it, you're going to need to create a utility method that will update the TreeView's SelectedItem every time the selected item or index in your ObservableCollection changes. This is not, however, the way I would recommend doing it.
The drop-down list (itemssource) of my combobox contains new product request items. I want to bind to legacy data that is not in the drop-down list. To complicate things I'm using multibinding with an IMultiValueConverter to combine fields for display. Also, the names of bound fields do not match the names of the properties I'm bound to.
The combobox itemssource is a list of NewProductRequests. From this NPR object NewProdNumber and NewProdName are combined for display in the drop-down list by my type converter. The ConvertBack method returns the values NewProdNumber and NewProdNumberCombinedWithName. These two values will be saved to database fields with slightly different names. For this example I'll call them DBProdRequestNumber and DBProdRequestTitle.
I've succeeded in displaying and saving new items. The problem is I haven't figured out how to display legacy data that is not in the list. It's not in the list because it no longer qualifies as a new product request.
Here is the problem XAML (the itemssource is set in code-behind):
<ComboBox x:Name="NPRComboBox" IsSynchronizedWithCurrentItem="False" IsEditable="False">
<ComboBox.SelectedItem>
<MultiBinding Converter="{StaticResource combineNPRStuffMultiConverter}">
<Binding Path="DBProdRequestNumber" UpdateSourceTrigger="PropertyChanged"/>
<Binding Path="DBProdRequestTitle" UpdateSourceTrigger="PropertyChanged"/>
</MultiBinding>
</ComboBox.SelectedItem>
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock DataContext="{Binding}">
<TextBlock.Text>
<MultiBinding Converter="{StaticResource combineNPRStuffMultiConverter}">
<Binding Path="NewProdNumber" UpdateSourceTrigger="PropertyChanged"/>
<Binding Path="NewProdNumberCombinedWithName" UpdateSourceTrigger="PropertyChanged"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
A similar problem with a datagrid and combobox I solved using a DataGridTemplateColumn.CellEditingTemplate based on this MSDN Magazine example from Julie Lerman. Of course, in this case I'm not using a datagrid.
Thanks in advance for any help.
This answer (to my own question) was pulled from a comment in the NathanAW answer:
Unfortunately I can't include legacy items in the ItemsSource. The list is from a web service that is out of my control. I devised a kludgy solution which I don't really like (but it works)...Since I know the combobox is needed only for new records it is visible only when the user clicks "Add". In the same location I placed a textbox bound to the legacy data that is visible when NOT in add mode. So, I toggle the visiblity of each control as the app switches in and out of add mode. I'm sure there is a better way!
It seems that you might be able to simplify this by not using a Multi-Binding converter. If you have a collection of NPR objects, then you can set that as the ItemsSource for the listbox. Then use the DataTemplate to format how you want that item displayed.
With this setup, you can construct a template that shows multiple fields from the NPR object in a single TextBlock using something like:
<ComboBox
x:Name="NPRComboBox"
IsSynchronizedWithCurrentItem="False"
IsEditable="False"
SelectedItem={Binding SelectedNPR, Mode=TwoWay}"
>
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock>
<Run Text="{Binding Path=NewProdNumber, UpdateSourceTrigger=PropertyChanged, Mode=OneWay}" />
<Run> - </Run>
<Run Text="{Binding Path=NewProdNumberCombinedWithName, UpdateSourceTrigger=PropertyChanged, Mode=OneWay}" />
</TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
If you have additional properties on the NPR object that you'd like to access, you can add an additional section to the template.
Notice that the "selected" item is bound two-way back to a property on your ViewModel (or code-behind, or whatever). This would be something like:
public NPR SelectedNPR
{
get { ... }
set
{
...
// don't forget INotifyPropertyChanged
...
}
}
EDIT
Here is a sample that seems to do what you've indicted about showing legacy data in the "SelectionBox", but not in the drop down list. To test this, try running it in KaXaml or something. Then start typing "Hello 3" and see that it suggests "Hello 30". This indicates that the Combo knows about the item. Now drop the list down and see that it isn't in the list. If you arrow down with the arrow keys, it skips from "Hello 20" to "Hello 40".
The next step would be to setup your templates so that the ListBoxItem template's Visibility is bound to "IsLegacy" on your NPR object. Then add both legacy and new items to the ItemsSource collection and bind to the list.
<ComboBox IsEditable="True">
<ComboBoxItem >Hello 10</ComboBoxItem>
<ComboBoxItem >Hello 20</ComboBoxItem>
<ComboBoxItem Visibility="Collapsed">Hello 30</ComboBoxItem>
<ComboBoxItem >Hello 40</ComboBoxItem>
</ComboBox>
I assume this is possible but not sure how to do it. I need to pass the value of a class level variable to a converter, from within side a data template.
<DataTemplate x:Key="ResponseItemTemplate">
<StackPanel Orientation="Horizontal" >
<StackPanel.Visibility>
<MultiBinding Converter="{StaticResource VisibilityConverter}">
<Binding Path="Key"/>
<Binding Path="CurrentLanguage"/>
</MultiBinding>
</StackPanel.Visibility>
<TextBox Width="200" Text="{Binding Value}" />
</StackPanel>
</DataTemplate>
The 'Key' value exists on the response item for the data template so this gets passed correctly, whereas the CurrentLanguage is a class variable and I can't get that to pass properly to the converter. Any ideas?
Thanks for the replies, this is what I needed to use in the end:
<Binding Path="DataContext.CurrentLanguage" RelativeSource="{RelativeSource FindAncestor, AncestorType={x:Type Window}}"/>
You can use the binding object as follows:
<Binding Source="{x:Static local:DataObject.MyData}" />
See: http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/c94682e5-ad16-42f9-973f-fd7588a9c0b5.
If you define the converter as a resource, which you have, you can access it in the code behind. Once you have the converter you can then set a property on it.
var myVisConverter = (VisibilityConverter)window.Resources["VisibilityConverter"];
myVisConverter.CurrentLanguage = ...
EDIT Ok, if you're trying to get access to the parent DataContext from within the DataTemplate, there's a couple of options. Easiest is to name the control with the correct DataContext, then bind to that control like so...
<Binding Path="DataContext.CurrentLanguage" ElementName="nameGivenToElement" />
Josh Smith wrote an article with more ways of getting inherited DataContexts.