I have this ListBox:
<ListBox Name="lbAFiles" HorizontalAlignment="Left" Height="100" Margin="318,61,0,0"
VerticalAlignment="Top" Width="481">
<ListBoxItem>
<TextBlock>Line1<LineBreak/>Line2</TextBlock>
</ListBoxItem>
</ListBox>
I have my own object with several properties that i want to fill inside my ListBox instead of the line:
<TextBlock>Line1<LineBreak/>Line2</TextBlock>
How can i do that with code behind ?
lbAFiles.Items.Add("Line 1");
lbAFiles.Items.Add("Line 2");
That said, it would be better to use MVVM and a ViewModel, but you asked how to do it in code behind.
Whatever the object you want to add there, you could pull the properties into the string you're adding.
Another (better) option would be to add this object directly to the ListBox, and use a DataTemplate to give it a "look" (otherwise you will just get the ToString value of that object).
And a much better option is to use data binding.
Related
Any help on this really appreciated. In summary I'm trying to databind to properties of a custom class instantiated in xaml that then forms the content of a templated listboxitem (phew!).
I have a simple c# class called MenuItem. It has two properties:
- Heading
- Icon
Concentrating on just one of those menu items (i.e. to provide a simple example of where I am stuck) If I do this (with the values hard coded) it works fine:
<ListBox>
<ListBoxItem ContentTemplate="{StaticResource MenuItemTemplate}">
<myclasses:MenuItem Heading="News" IconImage="News.png"/>
</ListBoxItem>
</Listbox>
Where MenuItemTemplate is an appropriate DataTemplate in the resources section binding each property) containing lines such as:
<TextBlock x:Name="tbHeading" Text="{Binding Heading}">
Wheareas when I try to use binding to set the Heading property it falls over (AG_E_PARSER_BAD_PROPERTY_VALUE error)- e.g.:
<ListBox>
<ListBoxItem ContentTemplate="{StaticResource MenuItemTemplate}">
<myclasses:MenuItem Heading="{Binding NewsHeading, Mode=OneWay}" Icon="News.png"/>
</ListBoxItem>
<Listbox>
I've wondered if it is because I'm doing some kind of double binding (i.e. the template is binding to a value on the MenuItem class that needs to be bound) and that's not possible? I've tried having the properties declared as dependency properties but no difference (although I only learned about those today so I may be missing something).
I know I could set the menuitem objects up in the view model, and bind from there, but I would like to understand why the above doesn't work (as for my purposes there are advantages in constructing the menu items in the xaml).
Thank you!!!!
Ian
thanks for sticking with this. I agree the listbox might not be needed - but even if I reduce it to just one item in a contentcontrol:
<ContentControl ContentTemplate="{StaticResource MenuItemTemplate}">
<myclasses:MenuItem Heading="{Binding NewsHeading, Mode=OneWay}" IconImage="News.png"/>
</ContentControl>
I still have the same problem - which is that I can get databinding to work within the content of a contentcontrol (prior to it being presented by the datatemplate referred to in ContentTemplate) using purely xaml.
I.e. the above bit of xaml doesn't work - it throws an error on the bit that binds the NewsHeading:
Heading="{Binding NewsHeading, Mode=OneWay}
So I am trying to understand whether what I'm doing is impossible, or whether it is but I'm doing it wrong.
Thanks.
Assuming that you have multiple MenuItem classes (because you're putting them in a listbox and ti wouldn't make sense to do that if you just had one). You need to bind the collection to the ItemsSource property of the ListBox.
Somehting like this:
<ListBox ItemsSource="{Binding MyMenuItems}">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Heading}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Note that the above assumes you've set the DataContext on the page to an object with a property called MyMenuItems which is a collection of your MenuItem objects.
To see a full example of this, look at the default code created when you create a new "Windows Phone Databound Application".
Edit:
Based on your comments, it seems that a ListBox is not the most appropriate solution to your needs. A ListBox is designed/intended to take a collection of items and display them in a list.
If you have a number of different objects which you know about at design time and simply wish to have them one on top of another (giving the appearance of a list) you could simply put them inside a ScrollViewer and/or a StackPanel (or other appropriate container). Plus, you would still be able to databind if you did it this way.
I have a large number of ViewModel classes. For each of these classes, there is a corresponding .xaml file which is a 'UserControl'. In my App.xaml, I have them registered as DataTemplates, like so:
<DataTemplate DataType="{x:Type viewModel:MainMenuViewModel}">
<view:MainMenuView/>
</DataTemplate>
With the idea being that WPF will be able automatically swap in the necessary user controls at runtime. For example, this works:
<Grid>
<StackPanel>
<TextBlock Text="SuperApp" />
<ItemsControl>
<ViewModels:MainMenuViewModel/>
</ItemsControl>
</StackPanel>
</Grid>
In that the entry "MainMenuViewModel" is automatically replaced by the MainMenuView, bound to the MainMenuViewModel. Great. My current goal is now this: I want to have a button, on, say, a view embedded in the MainMenuView, which opens a popup window, which will have a new ViewModel inside. The idea is to set it up so that I have a single 'generic' popup form, in which I embed an arbitrary ViewModel, and let WPF handle actually rendering it with DataTemplates, similar to the above. So I have a command bound to a button, like so:
<Button Command="{Binding Path=LaunchInStandaloneForm}" Content="Rip Out"/>
Which successfully creates a new window, sets the dataContext equal to the appropriate ViewModel, and shows the window.
The question is: How do I set up the XAML of this popup window so that it will render the appropriate DataTemplate for the ViewModel which is the DataContext? I've tried:
<Grid>
<ItemsControl ItemsSource="{Binding Path=.}">
</ItemsControl>
</Grid>
, but it comes up blank. Any pointers?
To set the ItemsSource to the DataContext, use ItemsSource={Binding}. That assumes that the DataContext is an enumerable collection of your View Model objects.
Updating with correct answer:
Use a ContentControl :)
Hope that helps.
The accepted answer here shows how to change templates at runtime. You should be able to dig out the answer from that. Any questions just shout.
How to modify silverlight combobox data display
Hope that helps
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 have two WPF list boxes. One is a list of lists (actually a List of ObservableCollection), the other is a list of all known instances of "Thingy".
Here's the datatemplate I'm using for the "thingy" class.
<DataTemplate DataType="{x:Type Model:Thingy}">
<StackPanel Orientation="Horizontal">
<CheckBox x:Name="ThingyInListCheckBox" Click="ThingyInList_Click"></CheckBox>
<TextBlock Text="{Binding Path=ThingyName}"></TextBlock>
</StackPanel>
Here's the XAML for the list boxes:
<ListBox
Name="ListOfGroups"
SelectionMode="Single">
</ListBox>
<ListBox
Name="ListOfThingys"
SelectionMode="Single">
</ListBox>
I have the data binding for the list boxes set up in code, because I'm too tired to figure out how to do it in XAML:
ListOfGroups.ItemsSource = InMemoryCache.ThingyGroups;
ListOfThingys.ItemsSource = InMemoryCache.Thingys;
What I want is the checkbox "ThingyInListCheckBox" to be checked if the 'thingy' object is in the list that is the selected item in the "ListOfGroups" listbox. So basically I need to bind it to the "Contains" method of the "ListOfGroups".SelectedItem while passing it the "ListOfThingys".SelectedItem as a parameter.
I'm tempted to do this all in code, but I'm trying to get a better understanding of XAML data binding because I hate myself and I want me to suffer.
Is this even possible, or have I hit the inevitable "wall of databinding" that exists in every other data binding system in the history of software development?
It is possible, in fact the hard thing is that there are many ways to do this and you have to choose one. None of them is a simple addition to your current code. However there is one way, by which you gain more than solving your problem. Actually, it is more of a pattern, called MVVM (some might argue about the naming).
Here is a small explanation on your example.
Suppose ThingyGroup has an IsSelected property, which is bound to the IsSelected property of the containing ListBoxItem. Again, suppose Thingy has a Group property too. Then you can use Group.IsSelected as a path to bind checkbox. Notice that there is still a small issue that IsSelected is a bool and IsChecked is a nullable bool.
A search on MVVM should give you concrete samples.
I'm working on a simple chat application. Currently the messages are binded to a custom-styled listbox like this (simplified XAML):
<ListBox ItemsSource="{Binding MessageCollection}">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Text}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Now I would like to be able to put images (like graphical smileys) into the displayed message text. Is there any way to achieve this using TextBlock (or any other standart component) or do I need to use some special control for this?
Thanks in advance
Just use the InlineUIContainer.
<TextBlock TextWrapping="Wrap">
<Run>Some text.</Run>
<InlineUIContainer>
<Image Source="http://sstatic.net/stackoverflow/img/apple-touch-icon.png" Height="20"></Image>
</InlineUIContainer>
<Run>Some more text.</Run>
</TextBlock>
The Content of a TextBlock is always just a series of Inlines, so you should use the InlineUIContainer. You can insert this container as one of the Inlines in your TextBlock wherever you want an Image to appear, alternating with text Runs. You could parse a message and at the same time keep adding the tokens (either text or images) that you find to the Inlines collection of the TextBlock.
If you want the Images actually inside the text (like an emoticon), then you are going to have to do some work. This sounds like one of the few times I would actually want a User Control, the point of which would be one that scans the Text looking for emoticon values and building a Data Template on the fly.
Remember that anything you can do in XAML you can do in code, so the code I'm thinking of would follow this general idea:
Scan text for emoticon values and
create a list of values for data
elements.
Create a DockPanel.
Foreach element in the List, add
either a TextBlock or an Image
(based on value).
Set this.Content to the DockPanel.
I think something like this is actually what you are looking for, but if you want just an Image, then the ValueConverter suggestion would work.
You could use a value converter to convert the text to another type which has a list of segments which are composed of either text or the smiley face (in the order in which they appear).
Then, you can use a data template to bind to that new type and display the text and smiley faces appropriately.
I also encountered this problem recently and I overcome this by
Creating an ListBox ItemTemplate containing an ItemsControl that has a WrapPanel in the ItemsPanelTemplate and then binding my string to the ItemsSource of the ItemsControl with a IValueConverter that houses all the logic.
Split out your words and query/search your emoticons strings, hyperlinks etc and create your TextBlock, Image, Hyperlink, Button elements and set your values and event handles.
In the function create a List<UIElement> and populate the List with the controls you have generated and return the List as the object in the Convert function of the IValueConverter.
Because you have the WrapPanel in there you get your wrapping done.
Use the Image element instead of the TextBlock and use a Converter to map the text value to the smile image.
<ListBox ItemsSource="{Binding MessageCollection}">
<ListBox.ItemTemplate>
<DataTemplate>
<Image Source="{Binding Text, Converter={StaticResource MyImageConverter}}"/>
</DataTemplate>
</ListBox.ItemTemplate>