I am using WPF and Mvvm and my ListView has its ItemSource bound to an ICollectionView. How do I handle selected item change event?
Originally I had a DataGrid's ItemSource bind to the same ICollectionView and setup the collection's CurrentChanged event. Everything works fine, but not the case for a ListView.
All you have to do, as Thomas mentioned is to bind the SelectedItem Attribute of the listbox to a property in the viewmodel. To make it clear, here's an example.
Here's my view
<Grid x:Name="LayoutRoot" Background="White">
<ListView ItemsSource="{Binding Contacts}" SelectedItem="{Binding SelectedContact, Mode=TwoWay}">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</Grid>
And here's my ViewModel
public class MainViewModel: ViewModelBase
{
ObservableCollection<ContactViewModel> contacts;
ContactViewModel selectedContact;
public ContactViewModel SelectedContact
{
get { return selectedContact; }
set {
selectedContact = value;
base.OnPropertyChanged("SelectedContact");
}
}
public ObservableCollection<ContactViewModel> Contacts
{
get { return contacts; }
set {
contacts = value;
base.OnPropertyChanged("Contacts");
}
}
}
Everytime you try changing the selection in the listbox you'll step into the setter of the SelectedContact.
set
{
contacts = value;
base.OnPropertyChanged("Contacts");
}
Through this, you'll know that the selected contact has changed.
Using the property SelectedContact, you'll also know which of the item in your collection is selected.
You can also bind a Collection property in the ViewModel to the SelectedItems attribute of the ListView if you want to implement multiple selection.
Just bind the SelectedItem of the ListView to a property of your ViewModel
Related
I have a user control (WaypointInfoControl) that I wrote that has a dependency property named TheGraphic as shown here:
public Graphic TheGraphic
{
get { return (Graphic)GetValue(TheGraphicProperty); }
set { SetValue(TheGraphicProperty, value); }
}
public static readonly DependencyProperty TheGraphicProperty =
DependencyProperty.Register("TheGraphic", typeof(Graphic), typeof(WaypointInfoControl), new PropertyMetadata(default(Graphic)));
I have a viewmodel that has a Waypoints property defined like this:
private ObservableCollection<Graphic>_Waypoints = new GraphicCollection();
public ObservableCollection<Graphic> Waypoints
{
get { return _Waypoints; }
set { RaiseAndSetIfChanged(ref _Waypoints, value); }
}
In my xaml, I have a ListView that I want to populate with Waypoints:
<ListView ItemsSource="{Binding Waypoints}" >
<ListView.ItemTemplate >
<DataTemplate >
<controld:WaypointInfoControl TheGraphic="????" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
How do I bind TheGraphic to the individual item in the ListView that it represents?
Your ItemsSource is bound to a collection of Graphic objects which means that the DataContext for each item in your ListView will be a single Graphic object. Since the DependencyProperty that you are looking to bind to is looking for the Graphic object you will just want to bind to the entire DataContext, you achieve this by using the binding markup extension without specifying a path (this just causes the binding to pull in the entire DataContext which in your case is the Graphic object that you are looking for).
So this should work:
<ListView ItemsSource="{Binding Waypoints}" >
<ListView.ItemTemplate >
<DataTemplate >
<controld:WaypointInfoControl TheGraphic="{Binding}" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
I have successfully passed the following Enum to a Combobox using the following:
public enum Color
{
Blue,
Green,
Yellow
}
public Color _color { get; set; }
public Type Colors
{
get { return typeof(Color); }
}
In the view I have the following:
<ComboBox ItemsSource="{Binding Colors, Converter={StaticResource enumConverter}}">
<ComboBox.ItemTemplate>
<DataTemplate>
<Grid>
<TextBlock Text="{Binding }" FontSize="14"/>
</Grid>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
This lets me pic a color in the box. What I want to do is to bind the chosen color to a property that's part of my viewmodel. I am very new to converters so I might be missing something.
You can bind the SelectedItem of the ComboBox to a property in your view model. The type of that property must match the type of the items generated by the enumConverter.
You can bind Combobox's SelectedItem to the property. I rename the Property to SelectedColor in the ViewModel. The PropertyChanged event is raised in the setter, so when you update the property, for example, from another method inside ViewModel, the view is notified and updated with the new value.
private Color _selectedColor;
public Color SelectedColor
{
get { return _selectedColor; }
set
{
_selectedColor = value;
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("SelectedColor"));
}
}
}
And in the XAML
<ComboBox ItemsSource="{Binding Colors, Converter={StaticResource enumConverter}}"
SelectedItem="{Binding SelectedColor}">
...
Have a WPFDatagrid binded to combobox using Datagridtemplatecolumn. Finding difficult to get the selectedItem of the combobox binding. Have found similar examples around but that's not resolving my problem.
Please find the code snippet of my XAML and the data structure below:
public class X
{
public X ()
{
abc = new ObservableCollection<P>();
}
public ObservableCollection<P> Y
{
get { return abc; }
set { abc = value; PropertyChanged("Y"); }
}
}
public class P
{
private string id;
private string name;
public string ID
{
get
{
return id;
}
set
{
id = value;
InvokePropertyChanged("ID");
}
}
public string Name
{
get
{
return name;
}
set
{
name = value;
InvokePropertyChanged("Name");
}
}
}
I have a datastructure defined above that implements the INotifyPropertychanged interface.
<controls:DataGrid Name="datagrid" AutoGenerateColumns="False" ItemsSource="{Binding XList}" Grid.Row="0"
SelectedItem="{Binding SelectedX, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
<controls:DataGrid.Columns>
<controls:DataGridTemplateColumn Header="Yl">
<controls:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<ComboBox ItemsSource="{Binding Y}"
IsSynchronizedWithCurrentItem="False" DisplayMemberPath="Name"
SelectedValue="{Binding Path=SelectedY, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, NotifyOnTargetUpdated=True}"
SelectedValuePath="SelectedY"
SelectedItem="{Binding SelectedY, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</DataTemplate>
</controls:DataGridTemplateColumn.CellTemplate>
</controls:DataGridTemplateColumn>
</controls:DataGrid.Columns>
</controls:DataGrid>
Now, in view model, have a observablecollection of List of X i.e., XList and that is binded to the datagrid in the XAML. and have Y within each row of the datagrid binded to the Combobox. Have a property as SelectedY, binded to the SelectedItem of the combobox.
Have also a property as SelectedX binded to the selectedItem of the datagrid, which works fine.
Issue is not able to get the Selected Item binding of the Combobox. Not able to set the selected item for the combobox when the selection has changed.
Can anybody help me out to set the selecteditem binding of the combo box?
Where is set your datacontext ?
You can do something like that :
<controls:UserControl x:Name=MainControl>
<controls:UserControl.DataContext>
<classpath:X/>
</controls:UserControl.DataContext>
<controls:DataGrid ItemsSource={Binding YourItemsContainer}>
<controls:DataGrid.Columns>
<controls:DataGridComboBoxColumn ItemsSource={Binding ElementName=MainControl,Path=DataContext.Y}
SelectedItem={Binding ElementName=MainControl,Path=DataContext.SelectedY}
DisplayMemberPath=Name />
</controls:DataGrid.Columns>
</controls:DataGrid>
</controls:UserControl>
The idea is to set a name to the root element connected to your datacontext, then you can access to it's datacontext property easily by the path. When you are inside of a template, the datacontext is the ItemsSource objects.
Hope it will help you a little !
in my View, there are a DataGrid and a TextBox, which is bound to the DataGrid's Items.Count property:
<DataGrid x:Name="dataGrid" ItemsSource="{Binding dataTable}"/>
<TextBox Text="{Binding Items.Count,ElementName=dataGrid,Mode=OneWay,StringFormat={}{0:#}}"/>
The ViewModel has a property (e.g. ItemsCount) which I'd like to be bound to the Items.Count property of the DataGrid, but have no idea, how to achieve this.
class ViewModel : INotifyPropertyChanged
{
public DataTable dataTable {get;set;}
public int ItemsCount {get;set;}
}
Maybe I could also use the Rows.Count property of the DataTable the DataGrid is bound to, but how would i bind or link the two properties in the ViewModel?
So I basically want the ItemsCount property to be synchronized with the dataTable.Rows.Count property.
A common way to achieve your requirements are to declare properties to data bind to the UI controls:
<DataGrid x:Name="dataGrid" ItemsSource="{Binding Items}" />
<TextBox Text="{Binding ItemsCount}" />
...
// You need to implement the INotifyPropertyChanged interface properly here
private ObservableCollection<YourDataType> items = new ObservableCollection<YourDataType>();
public ObservableCollection<YourDataType> Items
{
get { return items; }
set { items = value; NotifyPropertyChanged("Items"); NotifyPropertyChanged("ItemCount"); }
}
public string ItemCount
{
get { Items.Count.ToString("{0:#}"); }
}
UPDATE >>>
As #Sivasubramanian has added his own requirement to your question, in case you need to update the item count specifically by adding to your collection, you can manually call the NotifyPropertyChanged method:
Items.Add(new YourDataType());
NotifyPropertyChanged("ItemCount");
Below is the XAML snippet for my combo-box in a datagrid.
<data:DataGridTemplateColumn Header="Entry Mode">
<data:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<ComboBox ItemsSource="{Binding Path=EntryModeCombo,Mode=TwoWay}" DisplayMemberPath="Name" SelectedValuePath="Id" SelectedValue="{Binding Path=selectedEntryMode,Mode=TwoWay}" ></ComboBox>
</DataTemplate>
</data:DataGridTemplateColumn.CellTemplate>
</data:DataGridTemplateColumn>
Entrymode is an entity in the system and the Id and Name properties of this entity are used to set the DisplayMemberPath and SelectedValuePath of the combo.
public class A
{
private ObservableCollection<EntryMode> _EntryModeCombo;
public ObservableCollection<EntryMode> EntryModeCombo
{
get { return _EntryModeCombo; }
set
{
_EntryModeCombo = value;
RaisePropertyChanged("EntryModeCombo");
}
}
private string _selectedEntryMode;
public string selectedEntryMode
{
get { return _selectedEntryMode; }
set
{
_selectedEntryMode = value;
RaisePropertyChanged("selectedEntryMode");
}
}
}
In my viewModel, I am making an observable collection of the class A, and using that to bind a grid. All works well in the ADD mode, but in the edit mode, when I try to set the selected value of the combobox in the grid, it does not work. The population of the combo-box happens, but it remains unselected. Not sure why the selectedEntryMode property is getting set, but not affecting the combo selection in the grid.
Any suggestions will be appreciated.Thanks.
SelectedValue can only be used for getting value. not setting. use SelectedItem insted