So basically I have an list of an object that contains another List of objects. Lets say I have an List of the object Class. And Class contains a list of Students. Every student has a property Name as a simple string.
So basically what I want is the following:
The user can select a class using a ComboBox.
<ComboBox ItemsSource="{Binding Path=Classes}" DisplayMemberPath="Name" />
That works.
After selecting an Item from that ComboBox, the user should see a list of every student in that class (remember the property Name in Students)
I have created a simple ItemsControl for that purpose.
<ItemsControl ItemsSource="{Binding Classes}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Label Content="Name of the Student">
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
My question is: How do I get access to the students name in my label?
Your view model should have a SelectedClass property, which would be updated by binding it to the ComboBox's SelectedItem property:
<ComboBox ItemsSource="{Binding Classes}"
SelectedItem="{Binding SelectedClass}" .../>
You would then bind the ItemsControl to the Students collection of the selected Class like this:
<ItemsControl ItemsSource="{Binding SelectedClass.Students}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Note that the view model must implement the INotifyPropertyChanged interface and fire the PropertyChanged event when SelectedClass changes.
In a quick and dirty approach without a SelectedClass view model property, you could also directly access the ComboBox's SelectedItem like this:
<ComboBox x:Name="cbClasses" ItemsSource="{Binding Classes}" ... />
<ItemsControl ItemsSource="{Binding SelectedItem.Students, ElementName=cbClasses}">
...
Related
I have an ItemsControl with ListViews inside to make a custom grid like layout
Here is roughly what the code looks like to do this, names changed and irrelevant styling is removed.
Each ListView is created by an instance of ItemsSubList and therefore there is no set amount of listboxes or properties to be made.
Does anyone know How I would be able to bind the SelectedItem property of each listbox out somehow, into a list preferably.
<ItemsControl ItemsSource="{Binding Items}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<ListView ItemsSource="{Binding ItemsSubList}"
DisplayMemberPath="ItemVersion"
SelectionMode="Single"
Width="100"
VerticalAlignment="Top"
Background="#282828"
BorderBrush="#282828">
</ListView>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
I would solve it in your Model.
Your datacontext seems to be a class with a property Items of type ObservableCollection<MyItem> and your class MyItem then as a property ItemsSubList of type ObservableCollection<MySubItem>. Is that right?
The datacontext of your ListView is the instance of type MyItem. You can add a Property SelectedSubItem to your class MyItem and bind it with Two-way-binding to your listbox.SelectedItem.
And then in your main class, that holds your model and where the property Items lives, there I would add a property
public List<MySubItem> SelectedSubItems => Items.Select(i => i.SelectedSubItem).ToList();, a property that dynamically selects all selected subitems from all your items.
I've a ObservableCollection, when I want to display this ObservableCollection with CheckBox I am simply binding the contents to CheckBox but when I want to display the same collection by using ComboBox I am unable to do that. Any suggestions?
XAML: Display collection using CheckBox --WORKS
<ItemsControl ItemsSource="{Binding Synonyms}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" Margin="0,5,0,0" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<!--Display items in CheckBox-->
<CheckBox Content="{Binding Display}" Margin="10,0,0,0" /> // Display is the collection.
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Output:
XAML: Display collection using ComboBox --NOTHING OVER HERE
<ItemsControl ItemsSource="{Binding Synonyms}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" Margin="0,5,0,0" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<!--Display items in ComboBox.-->
Approach - 1
<ComboBox>
<ComboBoxItem Content="{Binding Display}"/>
</ComboBox>
Approach - 2
<ComboBox ItemsSource="{Binding Path=Synonyms}" DisplayMemberPath="Display"/>
Approach - 3
<ComboBox >
<ComboBox.ItemTemplate>
<DataTemplate>
<Border BorderBrush="Green" BorderThickness="1" Padding="5">
<TextBlock Text="{Binding Path=Display,StringFormat='Display: {0}'}" />
</Border>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Output:
I want to display items(one,two,three, etc.) inside oneComboBox with Select All option. I've tried several approaches but nothing. What am I missing here?
The checkbox is not designed to hold multiple items unlike the Combobox so implementing a system designed for the checkbox is not relevant for the combobox.
To solve your issue, remove the combobox from the ItemsControl and have it stand on its own:
<ComboBox ItemsSource="{Binding Synonyms}" DisplayMemberPath="Display"/>
Which tells the combobox to bind its ItemsSource to the data context which is unspecified, which is fine, so it then gets it's parent's data context. That process works its way up to each parent until it finds a bound data context (most likely the page's datacontext to a VM instance).
Assuming that the data context is valid at some point in the visual tree, it will bind to that instance and look for a property named Synonyms. From the Synonyms property it will use that as a list to display items.
To show (display) text in the combobox (instead defaulting to the item's ToString()) the combobox will show the string from the item's property Display.
Giving a list of items in one drop down.
The short answer, is you should use a ComboBox as the root element, not ItemsControl. CompboBox is just a specialized version of ItemsControl.
<ComboBox ItemsSource="{Binding Synonyms}" DisplayMemberPath="Display"/>
The longer answer.
ComboBox derives from ItemsControl, so you get all the features the base class, plus additional features.
ItemsControl (and its derived classes) provides a way of repeating a set of data in the UI. The DataTemplate is where you specify what UI you want for each "row" of data in the Synonyms source.
What you are doing is asking Silverlight to create a separate ComboBox for each underlying data row.
You can still use a DataTemplate within the ComboBox. Like this.
<ComboBox ItemsSource="{Binding Synonyms}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<!--Display items in CheckBox-->
<TextBox Text="{Binding Display}"
Margin="10,0,0,0"
FontWeight="Bold" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
I have two ListView, each bound to a specific collection in my ViewModel and I want to be able to select only one item globally.
Each ListView has its SelectedItem property bound to the same property in the ViewModel.
My probleme is as follow: when I select an item in a ListView, and then select another item in the other ListView, the first item stays selected.
I could achieve this with some code-behind, but I want to know if a pure XAML solution exists.
XAML:
<ListView SelectionMode="Single" ItemsSource="{Binding Path=MyList1}" SelectedItem="{Binding Path=MySelectedItem}">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<ListView SelectionMode="Single" ItemsSource="{Binding Path=MyList2}" SelectedItem="{Binding Path=MySelectedItem}">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Title}" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
I finally got it working, by just replacing SelectedItem by SelectedValue.
In this use case, both properties have the same behaviour, but the latter one handles correctly the unselection if the bound selected item is not in the list.
You need to use Mode=TwoWay in your SelectedItem. It should work.
I have a DataTemplate that is loading a list of ~7000 items in a list for a combobox. Currently the ItemsSource is bound to a property in the data context of the DataTemplate, however this means that for each instance of the DataTemplate the system is loading all 7k objects, which is slowing down the system by quite a bit.
Ideally I want to be able to load the list once and use it for all instances. The obvious solution to me is using a resource defined in the Window.Resources section. However I can't figure out how this should work, and more importantly, how that resource should be populated via the MVVM pattern.
Current code which loads the ItemsSource for each DataTemplate instance
<DataTemplate>
<ComboBox SelectedItem="{Binding SelectedItem}" ItemsSource="{Binding ItemsSource}" />
</DataTemplate>
Attempt at solving the problem:
<Window.Resources>
<ResourceDictionary>
<sys:Object x:Key="ItemItemsSource" />
</ResourceDictionary>
</Window.Resources>
<DataTemplate>
<ComboBox SelectedItem="{Binding SelectedItem}" ItemsSource="{Binding Source={StaticResource ItemItemsSource}}" />
</DataTemplate>
Update
Each DataTemplate has its own DataContext which means each instance of the data template has its own ItemsSource, which will populate at DataContext initialiser.
Update 2
The ideal way in my mind to solve this is to have a property in the DataContext/VM of the Window that they Combobox is bound too. Is this possible? Something like:
public class WindowsViewModel
{
public List<Object> SharedItemSource { get; set; }
}
<DataTemplate>
<ComboBox SelectedItem="{Binding SelectedItem}" ItemsSource="{Binding <Some Binding To SharedItemSource>}" />
</DataTemplate>
Where is the slow down ?
If it is when you show the ComboBox's popup, maybe you can try to use virtualization like this :
<DataTemplate>
<ComboBox SelectedItem="{Binding SelectedItem}" ItemsSource="{Binding ItemsSource}">
<ComboBox.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel />
</ItemsPanelTemplate>
</ComboBox.ItemsPanel>
</ComboBox>
</DataTemplate>
Create a MainViewModel for your window or what ever control all your combobox's are in ,
cs:
public class MainViewModel
{
private List<object> _itemsSource;
public List<object> ItemsSource
{
get { return _itemsSource; }
set { _itemsSource = value; }
}
}
xaml:
<DataTemplate>
<ComboBox SelectedItem="{Binding SelectedItem}"
ItemsSource="{Binding Path=DataContext.ItemsSource,
RelativeSource={RelativeSource AncestorType=ItemsControl}}"/>
</DataTemplate>
If you have property defined in VM, then that will be loading just once when you will be instantiating it and be served as source for all the comboboxes.. not every combobox create its itemsSource.. it just consume it to generate its items.. so whether you put your itemsSource as Resource or in Datacontext is one and the same thing here.
I'm trying to bind KeyValuePair Elements from a Dictionary to a ItemsControl.
My Dictionary has 15 Elements and the following code shows me 15 TextBoxes:
<WrapPanel Name="PersonsWrapPanel" Grid.Row="0">
<ItemsControl ItemsSource="{Binding Persons}" >
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel Orientation="Horizontal" Width="auto">
</WrapPanel>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBox Text="{Binding Value.Text}"></TextBox>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</WrapPanel>
Unfortunately without any TextBox content (which would be Key or Value).
Any ideas?
Perhaps try binding directly to the values of the dictionary:
ItemsSource="{Binding Persons.Values}"
If I am understanding your XAML properly, each object in the dictionary has a field called "Text" to which you are trying to bind. If so and you make the above changes, you will need to change your DataTemplate as well:
<TextBox Text="{Binding Text}" />
See this article for more info. HTH.
I solved it by using this line:
<TextBox Text="{Binding Value, Mode=OneWay}"></TextBox>
The code on http://www.dev102.com/2008/03/07/binding-a-wpf-control-to-a-dictionary/ doesn't seem to work.
Let us say you have a Dictionary called RowValues, with both the [key, value] defined as [string, string].
Now to bind to the Value Pair of this dictionary, you can do the following:
<ItemsControl ItemsSource="{Binding RowValues.Values}" >
To display the text (Value), you can bind as:
<TextBlock Text="{Binding}"/>