Develop Reference

C# WPF SelectionChangedEvent - reset selection - better options?

I have a datagridview populated with items and I am using a SelectionChanged event to populate textboxes from that data when selected.
If I make a selection, everything works. If I click elsewhere in the App and then come back to click the SelectionChanged event again on the same item - it doesn't work.
According to MSDN:
"This event occurs whenever there is a change to a selection."
MSDN SelectionChangedEvent
So it appears that despite clicking elsewhere, resetting the Textboxes - the selected item is not changing as the SelectionChanged event no longer triggers - click on another item and it works, click back again and it works - but click on it, reset textboxes, click it again - nothing happens, this includes clicking in the datagridview itself in a blank area.
XAML:
<DataGrid x:Name="TimeView" Grid.Row="1" Grid.Column="3"
Grid.ColumnSpan="3" Grid.RowSpan="4" Margin="10 50 10 10"
CanUserAddRows="False" Visibility="{Binding StartTiming}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<cal:ActionMessage MethodName="SelectedTimeChangeEvent">
<cal:Parameter Value="$eventArgs" />
</cal:ActionMessage>
</i:EventTrigger>
</i:Interaction.Triggers>
</DataGrid>
ViewModel
public void SelectedTimeChangeEvent(SelectionChangedEventArgs e)
{
foreach (TimeData addedRow in e.AddedItems)
{
TbID = addedRow.ID;
TbDate = addedRow.Date;
TbStartTime = addedRow.StartTime;
TbDescription = addedRow.Description;
}
}
Since I am using MVVM and Caliburn, TimeView is connected to an ICollection, which is in turn connected to an ObservableCollection:
private ObservableCollection<TimeData>? _timeCollection;
public ObservableCollection<TimeData>? TimeCollection
{
get { return _timeCollection; }
set
{
_timeCollection = value;
NotifyOfPropertyChange(() => TimeCollection);
}
}
private ICollectionView? _timeView;
public ICollectionView? TimeView
{
get { return _timeView; }
set
{
_timeView = value;
NotifyOfPropertyChange(() => TimeView);
}
}
There is a work around, which is the following after populating the Textboxes:
TimeView = null;
TimeView = CollectionViewSource.GetDefaultView(TimeCollection);
This works, but I thought that there might be a "deselect" option that would be better than repopulating every time a selection is made, one of my Datagrids contains 15,000 items, and it is still instant, but seems overkill to populate it every time a selection is made.

i would recommend bindings, they automaticly reset when nothing is selected
<DockPanel>
<StackPanel DataContext="{Binding SelectedTime}" DockPanel.Dock="Left">
<TextBlock Text="{Binding ID}"/>
<TextBlock Text="{Binding Date}"/>
<TextBlock Text="{Binding StartTime}"/>
<TextBlock Text="{Binding Description}"/>
</StackPanel>
<DataGrid ItemsSource="{Binding TimeView}" SelectedItem="{Binding SelectedTime}">
...
</DataGrid>
</DockPanel>
public TimeData SelectedTime
{
get { return _selectedTime; }
set
{
_selectedTime = value;
NotifyOfPropertyChange(() => SelectedTime);
}
}
also there is this neet feature
protected virtual void SetValue<T>(ref T field, T value, [CallerMemberName] string propertyName = null)
{
field = value;
OnPropertyChanged(propertyName);
}
so you can write
set { SetValue(ref _selectedTime, value) }

Can't change ComboBox selection when bound to ObservableCollection (WPF)

I'm trying to create an edit form for editing properties of a custom set of TV Series objects. One of the properties holds a collection of all owned media formats (DVD, Blu-ray, etc) for that particular series that will be displayed in a ComboBox. Items are added to the ComboBox via a separate popup window and items are to be removed from the ComboBox by selecting the item and clicking a remove Button.
I can add new entries to the MediaOwned ComboBox just fine, but when I try to select a specific ComboBox item to test the remove Button I find that I can only ever select the first entry. Can someone please tell me if I've missed something embarrassingly obvious, thanks.
Here is the problematic property:
private ObservableCollection<string> _mediaOwned = new ObservableCollection<string>();
public ObservableCollection<string> MediaOwned
{
get { return _mediaOwned; }
set
{
_mediaOwned = value;
OnPropertyChanged(new PropertyChangedEventArgs("MediaOwned"));
}
}
Here are the other relevant code behind:
private void Window_Loaded(object sender, RoutedEventArgs e)
{
// Create binding for the ListBox.
Binding listBinding = new Binding();
listBinding.Source = show.Series;
listBinding.Mode = BindingMode.OneWay;
listBinding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
lbSeries.SetBinding(ListBox.ItemsSourceProperty, listBinding);
// Create binding for the ComboBox.
Binding myBinding = new Binding();
myBinding.Path = new PropertyPath("MediaOwned");
myBinding.Mode = BindingMode.TwoWay;
myBinding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
cbMediaOwned.SetBinding(ComboBox.ItemsSourceProperty, myBinding);
}
private void btnRemoveMedia_Click(object sender, RoutedEventArgs e)
{
Series series = (Series)lbSeries.SelectedItem;
series.MediaOwned.Remove(cbMediaOwned.Text);
}
And here is the XAML code:
<Border Style="{StaticResource PanelBorderStyle}" DockPanel.Dock="Left" Margin="0,8,8,0"
DataContext="{Binding ElementName=lbLists, Path=SelectedItem}">
<DockPanel VerticalAlignment="Top">
<StackPanel>
<ListBox x:Name="lbSeries" Style="{StaticResource BasicListStyle}" Width="180" Height="300"
DisplayMemberPath="Title" SelectionMode="Single" LayoutUpdated="lbSeries_LayoutUpdated">
</ListBox>
</StackPanel>
<StackPanel x:Name="editPanel" DataContext="{Binding ElementName=lbSeries, Path=SelectedItem}">
<StackPanel Orientation="Horizontal" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="0, 4, 0, 0">
<TextBlock Style="{StaticResource SmallFont}" Width="100">Title</TextBlock>
<TextBox x:Name="txtTitle" Style="{StaticResource TextBoxStyle}" Text="{Binding Path=Title, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Width="200" Margin="8, 8, 16, 8"></TextBox>
</StackPanel>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Left" VerticalAlignment="Top">
<TextBlock Style="{StaticResource SmallFont}" Width="100">Media owned</TextBlock>
<ComboBox x:Name="cbMediaOwned" Style="{StaticResource ComboBoxStyle}" Width="150" Margin="8,8,6,8"
></ComboBox>
<Button x:Name="btnAddMedia" Style="{StaticResource ToolbarButtonStyle}" Click="btnAddMedia_Click" Margin="0">
<StackPanel ToolTip="Add media">
<Image Source="Images/add.png" />
</StackPanel>
</Button>
<Button x:Name="btnRemoveMedia" Style="{StaticResource ToolbarButtonStyle}" Click="btnRemoveMedia_Click" Margin="4">
<StackPanel ToolTip="Remove media">
<Image Source="Images/remove.png" />
</StackPanel>
</Button>
</StackPanel>
</StackPanel>
</DockPanel>
</Border>
Alternatively I can also remove the binding code in the code behind and replace the ComboBox with the below code (but I still get the same problem - I can't select anything in the ComboBox):
<ComboBox x:Name="cbMediaOwned" Style="{StaticResource ComboBoxStyle}" Width="150" Margin="8,8,6,8" ItemsSource="{Binding ElementName=lbSeries, Path=SelectedItem.MediaOwned, UpdateSourceTrigger=PropertyChanged}"
SelectedItem="{Binding SelectedMedia, UpdateSourceTrigger=PropertyChanged}"></ComboBox>
SelectedMedia property:
private string _selectedMedia = "";
public string SelectedMedia
{
get { return _selectedMedia; }
set
{
_selectedMedia = value;
OnPropertyChanged(new PropertyChangedEventArgs("SelectedMedia"));
}
}

Here is my xaml:
<ComboBox x:Name="Models_ComboBox"
Width="110"
Text="Model"
ItemsSource="{Binding Models}"
SelectedItem="{Binding SelectedModel}"
DisplayMemberPath="Model"
MouseDoubleClick="Models_ComboBox_MouseDoubleClick"
SelectionChanged="Models_ComboBox_SelectionChanged"/>
Here are my VM properties:
private DataTable models;
public DataTable Models
{
get { return models; }
set
{
if (models != value)
{
models = value;
OnPropertyChanged(nameof(Models));
}
}
}
and
private DataRowView selectedModel;
public DataRowView SelectedModel
{
get { return selectedModel; }
set
{
if (selectedModel != value)
{
selectedModel = value;
if (value != null)
{
InitializeOptions(value["Model"].ToString());
}
OnPropertyChanged(nameof(SelectedModel));
}
}
}
As you can see, the ItemsSource and the SelectedItem of the ComboBox are bound to two different properties in the ViewModel. The ItemsSource is bound to a DataTable populated from a Database. Once the user selects a Model, then there are other option ComboBoxes that are populated based on that selection.

Fixed the problem myself. I had a line of code that was automatically setting the SelectedIndex of the ComboBox without me realizing.

detect selecteditem details in ListBox from MVVM app in windows phone

I have the following view.xaml and I bind a collection(SavedTracksCollection from viewmodel) to this list box and it displays the items in UI.
<phone:PanoramaItem Name="MusicTracks" Header="Saved Tracks" >
<Grid>
<ListBox x:Name="list" ItemsSource="{Binding SavedTracksCollection}" SelectedItem="{Binding SelectedItemTrack,Mode=TwoWay}">
<ListBox.ItemTemplate>
<DataTemplate>
<Button Background="Red" >
<StackPanel Orientation="Vertical">
<TextBlock Text="{Binding TrackTitle}"/>
<TextBlock Text="{Binding TrackUri}"/>
</StackPanel>
</Button>
<DataTemplate>
</ListBox.ItemTemplate>
</Grid>
</phone:PanoramaItem>
And the i have the following property defined in my viewmodel(this viewmodel is set as data context for my view) for the selecteditem binding "SelectedItemTrack".And i am binding SavedTracksCollection to the itemsource of the list.
private SavedTracksModel _SelectedItemTrack;
public SavedTracksModel SelectedItemTrack
{
get {
return _SelectedItemTrack;
}
set
{
if (value!=null)
_SelectedItemTrack = value;
//RaisePropertyChanged("SelectedItemTrack"); I dont think we need this.Let me know otherwise.
}
}
private List<SavedTracksModel> _SavedTracksCollection = new List<SavedTracksModel>();
public List<SavedTracksModel> SavedTracksCollection
{
get
{
return GetSavedTracks();
}
set
{
this._SavedTracksCollection = value;
RaisePropertyChanged("SavedTracksCollection");
}
}
But i am not able to determine how do i capture the SelectedITem event when user selectes an item from the Listbox .Currently it doesn't trigger the set method of the SelectedITemTrack .Once i capture the event with the details of selected item binding "TrackUri" i want to go to a new page where i can play the track.
any idea how to fix the issue ?

The first solution I can think of, why not just use the SelectionChanged event on ListBox?
<ListBox x:Name="list" ItemsSource="{Binding SavedTracksCollection}"
SelectedItem="{Binding SelectedItemTrack,Mode=TwoWay}"
SelectionChanged="List_OnSelectionChanged"/>
// in code behind
private void List_OnSelectionChanged(object sender, SelectionChangedEventArgs e)
{
// navigate here after validating the selected item
// or raise Command in your ViewModel programatically
}

Can I swap a buttons content databind to a different databind in code?

I cannot find any examples to make me understand how and if I can change the databind in c# at the click of a button on, in my case a toggleswitch, Basically I have 32 buttons in my app and those 32 buttons act the same but need different text with-in them depending on some toggle switches they are currently databinded so the text can be saved and retrieved from local storage but what values it gets depends on the state of these toggle switches.
So I currently have :
<Button x:Name="_ovButton1" Content="{Binding Source={StaticResource AppSettings}, Path=ovName1_1Value, Mode=TwoWay}" Margin="2,0,250,0" VerticalAlignment="Top" FontSize="14" Height="72" FontWeight="Bold" MouseLeftButtonUp="_ovButton1_MouseLeftButtonUp" MouseLeftButtonDown="_ovButton1_MouseLeftButtonDown" ClickMode="Hover" Hold="_ovButton1_Hold"/>
and I want when a user changes the state of a toggleswitch to change the
{StaticResource AppSettings}, Path=ovName1_1Value, Mode=TwoWay}
to for example:
{StaticResource AppSettings}, Path=ovName1_2Value, Mode=TwoWay}
but I cannot find any example that shows how to do that in c#
what code do I need to do that?

You can specify the target of databinding in code like this:
MyData myDataObject = new MyData(DateTime.Now);
Binding myBinding = new Binding("MyDataProperty");
myBinding.Source = myDataObject;
myText.SetBinding(TextBlock.TextProperty, myBinding);
See more at http://msdn.microsoft.com/en-us/library/ms742863.aspx

-- Edit Note I don't have access to a WP8 Emulator to test this ---
In the view model it looks like this:
public List<string> Members
{
get { return _Members; }
set { _Members = value; OnPropertyChanged(); }
}
public MainVM()
{
// Simulate Asychronous access, such as to a db.
Task.Run(() =>
{
Thread.Sleep(2000);
Members = new List<string>() {"Alpha", "Beta", "Gamma", "Omega"};
});
}
The code behind on the main page sets the datacontext (shared with all the child controls) as such:
public MainWindow()
{
InitializeComponent();
// Set the windows data context so all controls can have it.
DataContext = new MainVM();
}
The Mainpage Xaml to bind to members is like this
<Button Height="30"
Width="80"
Margin="10"
DataContext="{Binding Members}"
Content="{Binding Path=[0] }" />
<Button Height="30"
Width="80"
Margin="10"
DataContext="{Binding Members}"
Content="{Binding Path=[1] }" />
<Button Height="30"
Width="80"
Margin="10"
DataContext="{Binding Members}"
Content="{Binding Path=[2] }" />
<Button Height="30"
Width="80"
Margin="10"
DataContext="{Binding Members}"
Content="{Binding Path=[3] }" />
The result is this visually:
I based this on my blog article Xaml: ViewModel Main Page Instantiation and Loading Strategy for Easier Binding for more info and a fuller example.

I think your best bet is going to be to use a collection of strings and bind to that collection. You can either change the collection when a toggle is switched, or keep 6 collections and bind to the collection that is for the toggle.
Xaml:
<ItemsControl x:Name="Buttons" ItemsSource="{Binding ButtonTextCollection}">
<ItemsControl.ItemsPanel>
<toolkit:WrapPanel/>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Button Width="100" Height="70" Content="{Binding}" Click="OnButtonClick"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Your code-behind would have the event handler for your button click
private void OnButtonClick(object sender, RoutedEventArgs e)
{
var text = ((Button) sender).Content.ToString();
// Send the text
}
Your ViewModel would hold the ButtonTextCollection property and would change based on the toggle.
public ICollection<string> ButtonTextCollection
{
get { return _buttonTextCollection; }
set
{
_buttonTextCollection = value;
OnPropertyChanged("ButtonTextCollection");
}
}
When you want to change the text, you would change the ButtonTextCollection
public void ChangeButtonText()
{
ButtonTextCollection = new Collection<string> {"A", "B",...};
}

Failing To Bind Multiple UI Components in WPF

Alright I tried my best but looks like I need help. I have a textbox, a listview and a button in my xaml file. Listview has two columns: Devicename and DeviceAddress. I have done a binding of both the listview and textbox in such a way, that whenever I select an item in listview(I2CDeviceList), the deviceaddress(2nd Column) gets displayed in my textbox.
XAML:
<TextBox PreviewTextInput="AddressBox_PreviewTextInput" Name="AddressI2C" Text="{Binding SelectedItem.I2CDeviceAddress, Path=AddressMessage, Mode=TwoWay, ElementName=I2cDeviceList}" />
<Button Content="I2C Read" Command="{Binding Path=I2CReadCommand}" Name="button9" />
<ListView Grid.Column="0" ItemsSource="{Binding I2CDeviceList}" SelectedItem="{Binding SelectedI2CDeviceList, Mode=TwoWay}" Height="100" HorizontalAlignment="Stretch" Name="I2cDeviceList" VerticalAlignment="Stretch" Width="Auto" >
<ListView.View>
<GridView>
<GridViewColumn Header="I2C Device" Width="Auto" DisplayMemberBinding="{Binding I2CDevName}" />
<GridViewColumn Header="I2C Device Address" Width="Auto" DisplayMemberBinding="{Binding I2CDeviceAddress}" />
</GridView>
</ListView.View>
</ListView>
Thus using SelectedItem.I2CDeviceAddress gives me the deviceaddress in my Textbox.
Now my view model has a property for the Button and the textbox and has the following method which gets invoked when button is clicked:
public void I2CReadCommandExecuted()
{
ReadMessage = string.Empty;
Byte[] buffer = new Byte[512];
int address;
string strValue = AddressMessage;
if (strValue.StartsWith("0x"))
{
strValue = strValue.Remove(0, 2);
address = Convert.ToInt32(strValue);
mComm.setAddress(address);
}
}
// This is for textBox
private string _AddressMessage = string.Empty;
public string AddressMessage
{
get
{
return _AddressMessage;
}
set
{
_AddressMessage = value;
NotifyPropertyChanged("AddressMessage");
}
}
// Property for ListView
public ObservableCollection<I2CModel> I2CDeviceList
{
get { return _I2CDeviceList; }
set
{
_I2CDeviceList = value;
NotifyPropertyChanged("I2CDeviceList");
}
}
// Property for Selected Item in ListView
private I2CModel _selectedI2CDeviceList;
public I2CModel SelectedI2CDeviceList
{
get { return _selectedI2CDeviceList; }
set
{
_selectedI2CDeviceList = value;
NotifyPropertyChanged("SelectedI2CDevSize");
}
}
Basically I have to remove the 0x from the value and store the hexadecimal value in my integer variable.
Here I am facing two issues:
When I put both Text="{Binding SelectedItem.I2CDeviceAddress, Path=AddressMessage, Mode=TwoWay, ElementName=I2cDeviceList}" the seelcted address from the listview doesnt appear in my textbox. The moment I remove Path=AddressMessage, Mode=TwoWay,, it works fine. How to make sure both of them work smoothly? Is their any other way I can get the selected item from the listview and display it in my textbox?
By using string strValue = AddressMessage; I am trying to save the content of AddressMessage in the string but when I debug my code, it always shows "null" even though I have "0x23"(hardcoded) in my textbox. Due to this I get the following error: Object reference not set to an instance of an object. at the beginning of if condition.
I tried my level best but it ain't happening. Am i missing something?

First of all there is no need to have seperate AddressMessage property. It can be done using SelectedI2CDeviceList. But still if you want to use it it can be achieved through below changes -
Set AddressMessage property when the selected item of listview changes
public I2CModel SelectedI2CDeviceList
{
get { return _selectedI2CDeviceList; }
set
{
_selectedI2CDeviceList = value;
AddressMessage = _selectedI2CDeviceList.I2CDeviceAddress;
NotifyPropertyChanged("SelectedI2CDevSize");
}
}
Also change the binding of textbox to below one:
<TextBox
Name="AddressI2C"
Text="{Binding Path=AddressMessage, Mode=TwoWay}" />
Hence whenever selected item of the listview changes it will set the content for textbox and when AddressMessage property is properly set you want get your second issue.
Hope this helps.