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.
Related
I have a Tree View, I am using a Text block inside my Tree view Item.I can not able to bind text for text block When I used "Data context" for my Treeview Item. Can any one help me in fixing this Issue.
here is my xaml code..
<TreeViewItem ItemsSource="{Binding}" DataContext="{Binding XYZ}">
<TreeViewItem.Header>
<StackPanel>
<Image Source="abc.png" />
<TextBlock Text="{Binding BindContent}"></TextBlock>
</StackPanel>
</TreeViewItem.Header>
</TreeViewItem>
in My View Model, I am using
private string _content;
public string BindContent
{
get{ return _content;}
set{_content= value;}
}
In my constructor I am setting value for Content...
It is working fine when I used static content (or) when I am not using
Data context for Treeview Item. but for some other reasons i need to use Data Context.
How can I bind Content for Text block When I used Data Context for Tree view Item...
Thanks in Advance.
I think the problem could be that you are not implementing the INotifyPropertyChanged or you are not raising the notify property changed event. By default the text is null, then you set it in your ViewModel's constructor, but if it is not INotifyPropertyChanged then the view will not be notified.
Hope this could helps you to solve the problem...
Two things you can do,
Make sure your viewmodel implements INotifyPropertyChanged as suggested by Raul Otario and you raise the event on property change,
Secondly, you can use relative source in your binding something like, UserControl if your xaml is on usercontrol else Window
<TextBlock Text="{Binding Path=DataContext.BindContent,
RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type UserControl}}}"/>
Hope it helps...
<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
I have a ComboBox in my wpf application.
It's ItemsSource is binded to some table in my DataSet.
I need the text property to be binded to another's object property . I doesn't work because the ComboBox doesn't want to get two DataContexts. How can I solve this problem?
<StackPanel Width="Auto" Height="Auto" MinWidth="296" Orientation="Vertical" x:Name="MyStackPanel">
<ComboBox x:Name="MyComboBox" ItemsSource="{Binding}" Text={Binding Path=MyProperty} />
</StackPanel>
In the code behind :
MyComboBox.DataContext = MyDataSet.Tables[MyTable];
MyStackPanel.DataContext = MyObject;
I want the ComboBox to show items from one DataContext but to show the text from another DataContext. How can I do it?
Don't use DataContext. Set the Source property of your bindings in XAML or create the bindings in code and set the Source property there.
Why are you assigning something to the datacontext of the stackpanel? From the looks of it, its not used.
Your code should work if MyDataSet.Tables[MyTable] returns an enumeration and contains a property called MyProperty.
What do you mean when you say that the combobox "doesn't want to get two DataContexts"?
Look into the properties IsEditable and IsReadOnly of the combobox.
Something like
<ComboBox x:Name="MyComboBox" ItemsSource="{Binding}" Text={Binding ElementName=MyStackPanel Path=DataContext.MyProperty} />
I would like to set up a datagrid so that whenever an item is added to its itemssource the datagrid scrolls down to show the last item.
The datagrid is inside a datatemplate, so i cannot set the X:name property and access it directly from the codebehind.
What I have in mind is to use a datagrid event that fires when a row is added and has the grid scroll itself.
Here's some psuedo code that outlines how I have things set up:
UI.XAML exerpt
<TabControl ItemsSource="{Binding Parents}" x:Name="ProductsTab">
<TabControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Key}"/>
</DataTemplate>
</TabControl.ItemTemplate>
<TabControl.ContentTemplate>
<DataTemplate>
<DataGrid Margin="5" ItemsSource="{Binding Value.Children}">
<DataGrid.Columns>
<Column Column definitions removed for your sanity/>
</DataGrid.Columns>
</DataGrid>
</DataTemplate>
</TabControl.ContentTemplate>
</TabControl>
UI.XAML.CS exerpt
public class UI
{
//Thanks to Dr. WPF for the ObservableDictionary class
public ObservableDictionary<string, Parent> Parents {get; set;}
}
Parent.CS
public class parent
{
public ObservableCollection<Child> Children {get; set;}
}
The datagrids are not editable.
In case you're wondering, I have read the post "How to autoscroll on WPF datagrid" the code in that post would work for me if I could find an event that fires whenever an item is added to the datagrid itemssource.
Any Ideas?
Combine the autoscrolling idea with the idea from this question or this MSDN thread: instead of listening to your grid's event to detect row additions, listen to the events from the ItemsSource.
Edit: Since you don't like that suggestion, you could try hooking LoadingRow, but I strongly suspect this will require EnableRowVirtualization = false in order to work (I haven't tried it). If your collection gets large, turning off row virutalization opens up the possibility of a serious performance hit.
you can access the DataGrid, even if it is in a DataTemplate, by doing a 'search' in the visual tree : VisualTreeHelper.GetChildCount // VisualTreeHelper.GetChild , then test again the type until you find your grid. And you might seek with same kind of methods the ScrollBar, and then you can hook an event handler and use a code-behind logic.
I've been going round in circles with this for a couple of days, and I'm hoping a WPF guru can see where I'm going wrong.
I'm setting CurrentViewModel in code. The Selected item of my ListBox and the Content of my ContentControl bind correctly. But when changing the selected item in the Listbox via the UI the CurrentViewModel is being set but the Content Control is not being updated.
I'm using a data template to map my Views and View Models.
<DataTemplate DataType="{x:Type ViewModel:MyViewModel}">
<View:MyView />
</DataTemplate>
I have a ListBox which is bound to an observable collection of ViewModels. The Selected Item is bound to the current view model.
<ListBox ItemsSource="{Binding MyViewModelCollection}" DisplayMemberPath="DisplayName" SelectedItem="{Binding CurrentViewModel, Mode=TwoWay}"/>
I also have a content control that is also bound to the CurrentView Model
<ContentControl Content="{Binding CurrentViewModel, Mode=TwoWay}"/>
This is the property that they are both bound to
public MyViewModel CurrentViewModel
{
get
{
return _currentViewModel;
}
set
{
if (_currentViewModel== value) return;
_currentViewModel= value;
OnPropertyChanged("CurrentViewModel");
}
}
I've edited the names for clarity and removed formatting information.
Any help greatly appreciated.
Cheers,
Daniel
EDIT: Came across the link How can I debug WPF bindings?. I set a break point on the Content binding and it does indeed only get called once when the binding is first set.
You should not be setting TwoWay as the mode on your ContentControl:
<ContentControl Content="{Binding CurrentViewModel, Mode=OneWay}"/>
This is because you intend your ContentControl to read the value, but never write it.
As an aside, you can also bind the ContentControl to the currently selected item in the collection, rather than to that property by doing this:
<ListBox ItemsSource="{Binding MyViewModelCollection}"
DisplayMemberPath="DisplayName"
IsSynchronizedWithCurrentItem="True"/>
<ContentControl Content="{Binding MyViewModelCollection/}"/>
The "slash" (/) at the end of the collection indicates the current item selected in the collection and setting that current item property is as simple as setting the IsSynchronizedWithCurrentItem equal to true.
A lot of times I find with this combination, I really don't need the extra property on my view model.
Anyway, I hope this helps.