I'm using listBox.ItemsSource = e.Result.Persons, which is a collection of persons. The listbox shows the actual object names when I would like it to show the first name of each person object. How can I do this?
use Listboxes ItemTemplate.
something like this.
<ListBox>
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding FirstName}"/>
</ListBox.ItemTemplate>
</DataTemplate>
</ListBox>
In addition to the method of binding specified by the other response, you could simply bind it as follows:
listBox.ItemsSource = e.Result.Persons.Select(d => new { FirstName });
Or use the dedicated "DisplayMemberPath" property, which do exactly what you want easily without any side effects (nor additional markup):
<ListBox DisplayMemberPath="FirstName" />
For more complicated item representations, use templates (see below).
You can override the ToString() method of the Persons object so that it display the first name of the person.
Related
I have this collection
ObservableCollection<string> Urls { get; set; }
inside my data context class. I have a binding to it in my list box:
<ListBox ItemsSource="{Binding Urls}">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBox Text="{Binding .}" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
The data is diplayed in the list box, the two corresponding-not-shown-here buttons with commands Add and Delete work as well, however, the changing the TextBox does not affect the contents of the collection.
I have tried Mode=TwoWay in binding, but I figured that it is turned on already. I have tried some other options like Validate=OnPropertyChange, however, there is still nothing get updated.
How to make the TextBox inside that templated items in ListBox actually update the Urls property of a datacontext class?
You cannot modify strings; use a wrapper class with one string property, then bind the TextBox to said property. That way the strings in the property can be replaced with the edited ones.
<StackPanel DataContext="{StaticResource Employees1}">
<ListBox ItemsSource="{Binding}" DisplayMemberPath="Name"
IsSynchronizedWithCurrentItem="True"/>
<Label Content="{Binding Path=Count}"/>
<Label Content="{Binding Path=Name}"/>
</StackPanel>
How does the binding for the labels get resolved? How is it decided that the content of the second label is bound to Employees1.Count (and not to Employee.Count), while the first label is bound to
Employee.Name and synchonized with the listbox selection? Also, what if I would like to bind the first label to Employee.Count instead?
(Employee has properties Name (and possibly Count), Employees1 is an ObservableCollection of type Employee).
EDIT: So, the question here is WHY the first label displays the number of employees in the ObservableCollection, while the second label displays the name of a specific employee in the collection, the one that is currently selected in the ListBox. Apparently, the first label binds to the entire collection, and the second label to a specific employee in the collection. But why, and how to control this behavior.
From MSDN Data Binding Overview, Binding To Collections, section "Current Item Pointer":
Because WPF binds to a collection only by using a view (either a view
you specify, or the collection's default view), all bindings to
collections have a current item pointer.
and section "Master-Detail Binding Scenario":
This works because when a singleton object (the ContentControl in this
case) is bound to a collection view, it automatically binds to the
CurrentItem of the view.
In your example, the second Label automatically binds to the current item of the default view of the Employees1 collection. The first Label would also bind like this, but since the item object does not have a Count property it apparently falls back to a binding to the Count property of the collection itself. However i don't know if the latter behaviour is documented somewhere.
As Blam says - the labels have no relationship to the listbox - I think what you're trying to do here is bind an observableCollection of Employees with properties Count and Name to the listbox..
To do this you'll need an ItemsTemplate in the listbox
<ListBox ItemSource={Binding Employees1}>
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<Label Content="{Binding Count}" />
<Label Content="{Binding Name}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Let me try and answer the questions.
An ObservableCollection has a property Count.
As for getting a single property on the second label it is making some assumptions.
You might not get the same behavior in other version of .NET.
Should not bind a control that displays a single value to a collection.
If you want the selected item from the ListBox see this link
enter link description here
In the below code, Combobox is wired to NameInfo object along with a converter.NameInfoConverter returns a format in which items in combobox are shown in a particular format (for eg: LastName, FirstName (Badge#) )
Now, when I set TextSearch.Text="{Binding NameInfo, Converter={StaticResource NameInfoConverter}, ConverterParameter=true}" on combobox; TextSearch doesn't work. When I set TextSearch.TextPath="Name", search itself works but doesnot get the correct format displayed in the selectionbox of combobox.
Any Ideas?
<StackPanel>
<ComboBox x:Name:"cmbName">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name,
Converter={StaticResource NameInfoConverter}, ConverterParameter=true}"/>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
</StackPanel>
You've probably hit a limitation in the API. I suggest you take an alternative route and bind directly to a property that is correctly formatted for your textblock.
If this is a serious app, you may want to look into using the MVVM pattern and place your converted/formatted property in the viewmodel. Otherwise, just create a new property on your databound class called NameInfo or something and do the conversion from that.
I have an ObservableCollection of addresses that I am binding to a ListBox. Then in the ItemTemplate I am Binding to the current address record using {Binding .}. This results in my addresses displaying using their ToString method which I have setup to format the address. All is good, except if I update properties on an individual address record the list in the UI does not update. Adds/Deletes to the list do update the UI (using the ObservableCollection behavior). If I bind directly to properties on the address the UI does update (using the INotifyPropertyChanged behavior of the Address object).
My question is, is there a way to notify the UI of the change to the object as a whole so that I can still use this syntax or do I need to punt and put a DisplayText property on my address type that calls the ToString method and bind to that? FYI, this is an MVVM architecture so I don't have the luxury of calling Refresh on the ListBox directly.
Thanks for any help/ideas.
<ListBox x:Name="AddressList" ItemsSource="{Binding Addresses}" Background="Transparent" BorderBrush="Transparent"
Width="200" HorizontalAlignment="Left">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding .}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
When you bind to the Address object itself, the object itself -- that is, its identity -- doesn't change, even though its properties do. WPF therefore doesn't know to refresh the binding in this case.
So yes, you need to bind to a notifying property (or properties) rather than the whole object. As you say, one way to do this is to create a DisplayText property, and raise the PropertyChanged event for that property whenever something that affects the display text changes. Another is to use multiple TextBlocks in a horizontally oriented StackPanel, each bound to a particular property e.g.
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding HouseNumber}" />
<TextBlock Text=", " />
<TextBlock Text="{Binding Street}" />
<TextBlock Text=", " />
<TextBlock Text="{Binding City}" />
</StackPanel>
The advantage of the second approach is that it gives you flexibility in the UI to change how addresses are displayed, e.g. multiple lines, formatting, etc.; the downside is that it gets complicated if you have conditional logic e.g. an optional flat number or second address line.
I tried to reproduce the problem and succeeded.
I activated the step-into-.NET debugging options, and saw that WPF does not listen to INotifyPropertyChanged if the path in the binding is empty.
What worked to get a change to be reflected in the list box is to replace the whole object in the ObservableCollection. This triggers the INotifyCollectionChanged, with the Replace action.
But this may not be acceptable in your case. And it could be seen more like a hack than a solid solution.
I'd seriously consider having a DataTemplate for Address. There you should bind to the exact properties you need (which would create the listener for INotifyPropertyChanged). It is more flexible than ToString() and you may encounter cases where you have a need for ToString() to do something for non-UI stuff, which would create a conflict. And honestly, ToString is not really meant for UI stuff.
I want to populate a TreeView with UserControls, but I only want the Name property to show up, not the entire UserControl. The following code gives me weird crashes as soon as I add something to myUCs:
C#:
var myUCs = new ObservableCollection<UserControl>();
MyTreeView.ItemsSource = myUCs;
XAML:
<controls:TreeView x:Name="MyTreeView">
<controls:TreeView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}"/>
</DataTemplate>
</controls:TreeView.ItemTemplate>
</controls:TreeView>
Does anyone know how to use a list of UserControls as an ItemSource for TreeViews?
I found one not so convenient workaround: instead of a List of UserControls, use a Dictionary, and change the XAML to:
<controls:TreeView x:Name="MyTreeView">
<controls:TreeView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Key.Name}"/>
</DataTemplate>
</controls:TreeView.ItemTemplate>
</controls:TreeView>
The same bug(?) exists in ListBox, a solution is provided here:
Use UIElements as ItemsSource of ListBox in Silverlight
That particular fix does not work for TreeView
You may have to create your own class that extends UserControl and override the ToString() method so that it returns the name property.