Develop Reference

Binding Errors on collapsed Gui Elements

I have a lot of bindings in a grid which are collapsed or visible based on the selecteditem in a treeview tree. so based on the object, the correct view pops up and the other collapses.
But I get lots of binding errors of the gui elements in the collapsed views. that is so, because I have a "myselecteditem" in the view model that fits to the view which is opened, but not to the collapsed ones.
is my approach stupid? can i suppress bindings for gui elemnts in a collapsed grid?
Code (shorted for lazy readers):
XAML:
<Grid x:Name="G_G_Content" Grid.Column="1">
<Grid x:Name="G_G_Abrechnung_Control" Visibility="Collapsed">
[...]
</Grid>
<Grid x:Name="G_G_Mitglied_Aktion" Visibility="Collapsed">
[...]
</Grid>
<Grid x:Name="G_G_Mitglied_Aktion_Nachweis" Visibility="Visible">
[...]
</Grid>
</Grid>
<TreeView
x:Name="G_tv_explorer"
Grid.Row="1"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
ItemsSource="{Binding TreeViewItemSource, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
SelectedItemChanged="G_tv_explorer_SelectedItemChanged"
TreeViewItem.Expanded="TreeViewItem_Expanded" />
C#:
private void G_tv_explorer_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
//set active treeviewitem
if (G_tv_explorer.SelectedItem != null)
{
//set treeview && ViMo
ViMo.TreeViewSelectedItem = e.NewValue;
RedrawGui();
ViMo.MySelectedItem = ((TreeViewItem)e.NewValue).Tag;
}
}
public void RedrawGui()
{
//redraw gui, dependant on selectedtreeviewitem
if (ViMo.TreeViewSelectedItem != null)
{
if(ViMo.TreeViewSelectedItem is string)
MessageBox.Show("Dummy");
else
{
//this is a placeholder
if (((TreeViewItem)ViMo.TreeViewSelectedItem).Header.ToString() == "Verwaltung")
{
G_G_Mitglied_Aktion_Nachweis.Visibility = System.Windows.Visibility.Collapsed;
G_G_Abrechnung_Control.Visibility = System.Windows.Visibility.Visible;
}
else if (((TreeViewItem)ViMo.TreeViewSelectedItem).Tag is MVVM.Model.Jahresabschluss)
{
G_G_Mitglied_Aktion_Nachweis.Visibility = System.Windows.Visibility.Collapsed;
G_G_Abrechnung.Visibility = System.Windows.Visibility.Visible;
}
}
}
}
Where RedrawGUI only sets the Grids Visible / collapsed based on the Object Type of the SelectedItem

UWP - get first child of Gridview

<GridView x:Name="MainGridStations" ItemsSource="{x:Bind Stations}" IsItemClickEnabled="True" ItemClick="GridView_ItemClick">
<GridView.ItemTemplate>
<DataTemplate x:DataType="local:Station">
<Grid x:Name="WantToSelectByCode">
<Grid Background="White" HorizontalAlignment="Center" Width="300" Height="200" VerticalAlignment="Center">
<Grid Background="#e4f0fc" Height="65" VerticalAlignment="Bottom" Opacity="0.8">
<TextBlock x:Name="StationName" Text="{Binding Name}" FontWeight="Bold" Foreground="#2c9a8b" HorizontalAlignment="Center" />
</Grid>
</Grid>
</Grid>
</DataTemplate>
</GridView.ItemTemplate>
</GridView>
I'm trying to select a child by index of a dynamically filled gridview but what i've tried always returns null.
Like so for the first child for example:
var container = MainGridStations.ContainerFromIndex(0);
var presenter = VisualTreeHelper.GetChild(container, 0) as GridViewItem;
What am I doing wrong here?

You can get the corresponding GridViewItem from the method ItemsControl.ContainerFromIndex(Int32) directly and don't need to use the VisualTreeHelper to get it again.
var container = MainGridStations.ContainerFromIndex(0);
GridViewItem gridViewItem= container as GridViewItem;
gridViewItem.Background = new SolidColorBrush(Colors.Red);
The container have been the corresponding GridViewItem got from the index.
Note that: since your inner Grid have a Background="White" property configuration, you can delete the code to see the effect more obviously using my above code to change the gridViewItem.Background.
---Update---
You must get the GridViewItem after the items loaded. You can try the code in your GridView_ItemClick event handler or the page's loaded event hander. Also pay attention to my above note that to get more obvious effect, please delete the Background="White" in your above xaml code.
private void MainPage_Loaded(object sender, RoutedEventArgs e)
{
var container = MainGridStations.ContainerFromIndex(0);
GridViewItem gridViewItem = container as GridViewItem;
gridViewItem.Background = new SolidColorBrush(Colors.Green);
}
//get the item here
private void GridView_ItemClick(object sender, ItemClickEventArgs e)
{
var container = MainGridStations.ContainerFromIndex(0);
GridViewItem gridViewItem= container as GridViewItem;
gridViewItem.Background = new SolidColorBrush(Colors.Red);
//var presenter = VisualTreeHelper.GetChild(container, 0) as GridViewItem;
}

GridView, ItemTemplate, DataTemplate binding in C# code behind

I have following working XAML and C# code behind:
<Grid x:Name="MainGrid" Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<GridView ItemsSource="{Binding}">
<GridView.ItemTemplate>
<DataTemplate>
<Grid Height="100" Width="150">
<Grid.Background>
<SolidColorBrush Color="{Binding Color}"/>
</Grid.Background>
<StackPanel>
<StackPanel.Background>
<SolidColorBrush Color="{Binding Color}"/>
</StackPanel.Background>
<TextBlock FontSize="15" Margin="10" Text="{Binding Name}"/>
</StackPanel>
</Grid>
</DataTemplate>
</GridView.ItemTemplate>
</GridView>
</Grid>
CODE behind:
public MainPage()
{
this.InitializeComponent();
var _Colors = typeof(Colors)
.GetRuntimeProperties()
.Select(x => new
{
Color = (Color)x.GetValue(null),
Name = x.Name
});
this.DataContext = _Colors;
}
This works fine.
But I want to do all the XAML part in C# code behind. In XAML, only MainGrid will be there, all its child elements and bindings needs to be done in code behind.
I have tried something like this in MainPage_Loaded event:
private void MainPage_Loaded(object sender, RoutedEventArgs e)
{
try
{
GridView gridView = new GridView()
{
ItemTemplate = new DataTemplate
{
//Don't know what to add here
}
};
Grid grid = new Grid();
Binding bindingObject = new Binding();
bindingObject.Source = this;
grid.SetBinding(Grid.BackgroundProperty, bindingObject);
//...
// Don't know how to add grid inside gridView in Code.
//...
MainGrid.Children.Add(gridView);
}
catch (Exception ex)
{
}
}

First of all I'd like to advise you not to create elements in code unless you have a real good reason to do so.
Regardless, considering that item templates are factory-like objects for controls (you 'spawn' a new set of controls for each item). You use the FrameworkElementFactory to model the subtree and then assign that the item template's VisualTree property.

how to delete a selected template in a listbox

i have a listbox which has a data template binded to task from xml file,i want to delete selected template on button click,but its throws me an exception "Operation is not valid while ItemsSource is in use. Access and modify elements with ItemsControl.ItemsSource instead."
here is the code for xaml
<TabItem>
<Canvas Height="700" Width="850">
<Canvas.Resources>
<XmlDataProvider x:Key="Tasks" XPath="tasks"
Source="http://store.tymesheet.com/templates/Graphic-Designer.xml"/>
<DataTemplate x:Key="tasktemplate1">
<Canvas Height="50" Width="850" >
<Label Content="{Binding XPath=name}" Height="30"
Width="170" Canvas.Top="10" Canvas.Left="150"
Background="LightGray"/>
<TextBox Height="30" Width="120" Canvas.Top="10"
Canvas.Left="370" Background="AliceBlue"/>
<Label Canvas.Left="500" Canvas.Top="10">$</Label>
<Button Tag="{Binding}" Click="deletebuttonclick"
Canvas.Top="12" Height="10" Width="30"
Canvas.Left="600"/>
</Canvas>
</DataTemplate>
</Canvas.Resources>
<ListBox ItemTemplate="{StaticResource tasktemplate1}"
ItemsSource="{Binding Path=ChildNodes, Source={StaticResource Tasks}}"
x:Name="tasklistbox" Height="700" Width="850"/>
<Label Canvas.Top="-18" Canvas.Left="185">Select Task</Label>
<Label Canvas.Top="-18" Canvas.Left="377" RenderTransformOrigin="0.58,0.462">Enter Bill Rates</Label>
<Button Canvas.Left="39" Canvas.Top="575" Width="139">Click to add the task</Button>
</Canvas>
</TabItem>
here is the code behind for delete button
private void deletebuttonclick(object sender,RoutedEventArgs e)
{
tasklistbox.Items.Remove(tasklistbox.SelectedItem);
}
where am i wrong?,help.thanx.

The error that you displayed is fairly self explanatory:
Operation is not valid while ItemsSource is in use. Access and modify elements with ItemsControl.ItemsSource instead.
Clearly, as you should know, you used the ItemsSource property on the ListBox:
<ListBox ItemTemplate="{StaticResource tasktemplate1}"
ItemsSource="{Binding Path=ChildNodes, Source={StaticResource Tasks}}"
x:Name="tasklistbox" Height="700" Width="850" />
The error is telling you to Access and modify elements with ItemsControl.ItemsSource instead. So instead of not doing what it says:
private void deletebuttonclick(object sender,RoutedEventArgs e)
{
tasklistbox.Items.Remove(tasklistbox.SelectedItem);
}
Try actually doing what it says:
private void deletebuttonclick(object sender,RoutedEventArgs e)
{
tasklistbox.ItemsSource = null;
}
Or even better:
private void deletebuttonclick(object sender,RoutedEventArgs e)
{
ChildNodes = null;
}
UPDATE >>>
So it seems that we have another new user that asks one thing and when given that thing asks for another thing without so much as a 'thank you'... shame... a real shame.
First you need to data bind to the ListBox.SelectedItem property so that you know which item is selected:
<ListBox ItemTemplate="{StaticResource tasktemplate1}" SelectedItem="{Binding Item}"
ItemsSource="{Binding Path=ChildNodes, Source={StaticResource Tasks}}"
x:Name="tasklistbox" Height="700" Width="850" />
This Item property should be of the same type as the items in the ChildNodes collection... if it's not clear enough - you need to add that property next to your collection property. Then to remove that item in your handler, you just need to do this:
private void deletebuttonclick(object sender,RoutedEventArgs e)
{
ChildNodes.Remove(Item);
}

If you want to remove the item, then I would suggest to create ObservableCollection of XmlNode and bind ItemsSource with that. I suggested to use ObservableCollection because it implements INotifyCollectionChanged so whenever list is updated target which in your case is ListBox will automatically be updated.
In code behind
(Add System.Collections.ObjectModel namespace to use ObservableCollection<T>)
public MainWindow()
{
InitializeComponent();
XmlDocument doc = new XmlDocument();
doc.Load("http://store.tymesheet.com/templates/Software-Developer.xml");
var taskList = doc.ChildNodes.OfType<XmlNode>()
.Where(node => node.Name == "tasks")
.SelectMany(node => node.ChildNodes.OfType<XmlNode>());
Tasks = new ObservableCollection<XmlNode>(taskList);
this.DataContext = this;
}
public ObservableCollection<XmlNode> Tasks { get; set; }
private void deletebuttonclick(object sender, RoutedEventArgs e)
{
XmlNode selectedNode = ((Button)sender).DataContext as XmlNode;
Tasks.Remove(selectedNode);
}
Of course you need to update XAML as well:
<ListBox ItemsSource="{Binding Tasks}"
ItemTemplate="{StaticResource tasktemplate1}"
x:Name="listBox" Height="700" Width="850"/>

How to attach an object to an event in C#/.NET?

I defined the following DataTemplate for a LibraryContainer:
<DataTemplate x:Key="ContainerItemTemplate">
<Grid>
<Border BorderThickness="1" BorderBrush="White" Margin="3">
<s:SurfaceTextBox IsReadOnly="True" Width="120" Text="{Binding Path=name}" Padding="3"/>
</Border>
<s:SurfaceButton Content="Expand" Click="SourceFilePressed"></s:SurfaceButton>
</Grid>
</DataTemplate>
The SourceFilePressed is the following:
private void SourceFilePressed(object sender, RoutedEventArgs e)
{
Logging.Logger.getInstance().log(sender.ToString());
e.Handled = true;
}
In the method SourceFilePressed who can I get the object that is binded to the SurfaceTextBox that is in the same grid as the pressed button? Can I somehow in the DataTemplate attach this object to the Click-Event?

If I parsed your question correctly, I think you could do this:
private void SourceFilePressed(object sender, RoutedEventArgs e)
{
var obj = (sender as FrameworkElement).DataContext;
}
To explain: the sender is the source of the event, so it's the SurfaceButton. It is a FrameworkElement and thus has a DataContext property. The DataContext is an inherited property, so unless you set it explicitly on the SurfaceButton, it will inherit it's DataContext from its parent (the Grid). The DataTemplate's DataContext is the data item it is templating, so you can see that the SurfaceButton will have that same object as its DataContext.