In my Silverlight 4 DataGrid control, I wanted to attach a very simple Behavior which executes a custom command on key Press - actually, commit the selected item in the DataGrid on ENTER key press.
While the Behavior actually works (see my code...
//.... in "OnAttached()..."
this.AssociatedObject.AddHandler(Control.KeyDownEvent, new KeyEventHandler(OnKeyDown), true);
private void OnKeyDown(object sender, KeyEventArgs e)
{
if (e.Key == Key.Enter)
{
InvokeCommand();
}
}
...) I have the problem, that the DataGrid seems to handle the ENTER key press itself and proceeds to the next row. Obviously, what happens is that the wrong Row is committed, because when I handle the Key Press, the row selectedion has already changed.
Here is the XAML:
<data:DataGrid
AutoGenerateColumns="False"
IsReadOnly="True"
ItemsSource="{Binding Path=Data}"
SelectedItem="{Binding SelectedRow, Mode=TwoWay}">
<data:DataGrid.Columns>
<data:DataGridTextColumn Binding="{Binding A}" />
<data:DataGridTextColumn Binding="{Binding B}" />
<data:DataGridTextColumn Binding="{Binding C}" />
</data:DataGrid.Columns>
<i:Interaction.Behaviors>
<behaviors:EnterBehavior Command="{Binding CommitCommand}" />
</i:Interaction.Behaviors>
</data:DataGrid>
Can you tell me how I can prevent the default ENTER event?
Guess it's a bit late now to help the OP, but I solved this by subclassing the data grid and overriding the KeyDown method to set e.Handled to true. That stops the default enter processing of the DataGrid, then your own actions can take effect.
(Obviously you have to replace instances of DataGrid in the XAML with YourCustomDataGrid)
public class YourCustomDataGrid : DataGrid
{
protected override void OnKeyDown(KeyEventArgs e)
{
// Stop "Enter" selecting the next row in the grid
if (e.Key == Key.Enter)
{
e.Handled = true;
}
base.OnKeyDown(e);
}
}
Don't rely on SelectedRow, use the row that raised the event in the first place as a parameter for your submit operation. See code below:
private void OnKeyDown(object sender, KeyEventArgs e)
{
if (e.Key == Key.Enter)
{
InvokeCommand(e.OriginalSource);
}
}
See if using the AddHandler overload with handledEventsToo can help you here. In certain cases, this allows you to get your handler invoked even if a previous handler already set handled=true.
Related
Imagine a UserControl with a ListBox having a CheckBox in a DataTemplate. The ItemsSource for the ListBox is some global list. The CheckBox has Checked/Unchecked events attached to it.
<ListBox ItemsSource="{Binding Source={x:Static a:MainWindow.Source}}">
<ListBox.ItemTemplate>
<DataTemplate DataType="{x:Type a:Data}">
<CheckBox Content="{Binding Path=Name}"
Checked="ToggleButton_OnChecked"
Unchecked="ToggleButton_OnUnchecked"
IsChecked="{Binding Path=IsEnabled}"
Padding="10"
VerticalContentAlignment="Center"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
I am logging loaded/unloaded/checked/unchecked events in the main window's log.
private void ToggleButton_OnChecked(object sender, RoutedEventArgs e)
{
Log("Checked");
}
private void ToggleButton_OnUnchecked(object sender, RoutedEventArgs e)
{
Log("Unchecked");
}
private void UserControl1_OnLoaded(object sender, RoutedEventArgs e)
{
Log("Loaded");
}
private void UserControl1_OnUnloaded(object sender, RoutedEventArgs e)
{
Log("Unloaded");
}
The main window features a dynamic list of UserControl1 instances (starting with just one). There are add/remove buttons that allow me to add more instances.
<UniformGrid Rows="2">
<DockPanel>
<Button DockPanel.Dock="Top" Click="Add">Add</Button>
<Button DockPanel.Dock="Top" Click="Remove">Remove</Button>
<ListBox x:Name="ListBox">
<local:UserControl1 />
</ListBox>
</DockPanel>
<ListBox ItemsSource="{Binding ElementName=This,Path=Log}" FontFamily="Courier New"/>
</UniformGrid>
The window's codebehind:
private void Add(object sender, RoutedEventArgs e)
{
ListBox.Items.Add(new UserControl1());
}
private void Remove(object sender, RoutedEventArgs e)
{
if (ListBox.Items.Count == 0) return;
ListBox.Items.RemoveAt(0);
}
When I run the app there is just one UserControl1 instance. If I add one more and then immediately remove one of them, then click the one and only checkbox on the screen, I see two "Checked" events logged. If I now uncheck it, there are two "Unchecked" events (even though "Unloaded" event was previously clearly logged. The hex numbers on the left show the output of a GetHashCode() which clearly shows the events were handled by distinct UserControl1 instances.
So even though one of UserControl1 gets unloaded, the events don't seem to get unsubscribed automatically. I have tried upgrading to NET Framework 4.8 to no avail. I see the same behavior. If I add 10 new controls and remove them immediately, I will observe 10 "Checked" or "Unchecked" events.
I have tried searching for a similar problem but could not find it. Is there something I am missing or did I just encounter a bug? Looking for workarounds.
Full source code is available on GitHub. https://github.com/wpfwannabe/datacontext-event-leak
In the MVVM pattern, the view is bind to the view model and doesn't survive it when the garbage collection do it's job.
In the example you provided, the view model is a static object and by definition can't be garbage collected, so the view can't neither be garbage collected.
There is no automatic unbinding since you can reuse an instance of an user control (it can be Loaded and UnLoaded multiple times).
The simplest¹ way to fix this memory leak is to do the unbinding on unload :
Wpf
// First give the ListBox a name
<ListBox x:Name="ListBox" ItemsSource="{Binding Source={x:Static a:MainWindow.Source}}">
Code behind
private void UserControl1_OnUnloaded(object sender, RoutedEventArgs e)
{
Log("Unloaded");
ListBox.ItemsSource = null;
}
1: The proper way is to wrap the static list in a dedicated list view model, make the view model disposable (to unbind the wrapper from the static list on dispose), dispose the view model on remove.
Here's a quick question. I have a DataGrid that looks like this:
<DataGrid ItemsSource="{Binding Path=Sections}" AutoGenerateColumns="False">
<DataGrid.Columns>
<DataGridTextColumn Binding="{Binding Path=ImportName, Mode=OneWay}" Header="Imported" />
<DataGridTextColumn Binding="{Binding Path=FoundName, Mode=TwoWay}" Header="Suggested" />
</DataGrid.Columns>
</DataGrid>
I want to bind "Suggested" column cells to a command in my VM, so that each time user clicks the cell for editing, my command would execute and show a dialog for the user. I've found an interesting solution to a similar problem described here: DataGrid bind command to row select
I like the fact that it manages this from XAML without any code-behind that attaches to the cell editing event. Unfortunately, I've no idea how to convert it in a way that would allow me to bind command to cells in a specific column, rather than the entire row. Any advice in regards to that?
You can use BeginningEdit event in the DataGrid control to handle this scenario. This event will fires before a row or cell enters edit mode. You can identify the selected column from the EventArgs.
Example:
private void dgName_BeginningEdit(object sender, DataGridBeginningEditEventArgs e)
{
if (e.Column.Header.ToString() == "Suggested")
{
//Do Operation
}
}
If you are using MVVM pattern, there are options to pass EventArgs to VM. If you are uusing MVVMLight Toolkit, there is an option called PassEventArgs and set it to TRUE.
In VM,
//Relay Command
private RelayCommand<DataGridBeginningEditEventArgs> _cellBeginningEditCommand;
public RelayCommand<DataGridBeginningEditEventArgs> CellBeginningEditCommand
{
get
{
return _cellBeginningEditCommand ?? (_cellBeginningEditCommand = new RelayCommand<DataGridBeginningEditEventArgs>(CellBeginningEditMethod));
}
}
//Command Handler
private void CellBeginningEditMethod(DataGridBeginningEditEventArgs args)
{
if(args.Column.Header.ToString() == "Suggested")
{
//Do Operation
}
}
Refreshing my datagrid when my observableCollection gets updated in the viewmodel have been a nightmare. After I discover the DataGrid won't respond to the events raised by the ObservableCollection I discovered DataGrid.Items.Refresh.
It does refresh but then the DataGrid loses focus. I have a simple list and I want to change a value when I press a key and then update. Its unacceptable the user have to pick the mouse again when using keyboard shortcuts ...
Here is a simple example:
<DataGrid x:Name="MyDataGrid" SelectionMode="Single" AutoGenerateColumns="False" IsReadOnly="True" KeyUp="MyDataGrid_KeyUp">
<DataGrid.Columns>
<DataGridTextColumn Header="First Name" Binding="{Binding Path=First}"/>
<DataGridTextColumn Header="Last Name" Binding="{Binding Path=Last}"/>
</DataGrid.Columns>
</DataGrid>
And the code behind:
private void MyDataGrid_KeyUp(object sender, KeyEventArgs e)
{
if (e.Key.Equals(Key.Space))
{
MyDataGrid.Items.Refresh();
}
}
p.s. In this example I'm setting the ItemsSource in my code behind and not binding to a ObservableCollection. Also i'm using just the codebehind and not a ViewModel but the problem is the same.
edit: The initial problem was that I wasnt using the NotifyPropertyChanged in my class. However, the problem here presented is still "open", I can't really understand the lost focus question when I do the Refresh()
Refreshing my datagrid when my observableCollection gets updated in the viewmodel have been a nightmare. - Why has this been a nightmare? Should be easy though.
Regarding your problem. Please try the following
private void MyDataGrid_KeyUp(object sender, KeyEventArgs e)
{
if (e.Key.Equals(Key.Space))
{
MyDataGrid.Items.Refresh();
MyDataGrid.Focus();
}
}
You can find the related doc here.
Edit
Let's try this one
private void MyDataGrid_KeyUp(object sender, KeyEventArgs e)
{
if (e.Key.Equals(Key.Space))
{
MyDataGrid.Items.Refresh();
FocusManager.SetFocusedElement(MyDataGrid);
}
}
For more information, please have a look here.
Scheduling the refresh via dispatcher worked for me (with a TreeView).
So instead of doing this (loses focus):
tree.Items.Refresh();
I do this (does not lose focus):
Dispatcher.BeginInvoke(new Action(() => tree.Items.Refresh()));
No idea why but it works for me.
As you know, in windows C#'s gridview, if we want to handle a click/double click event on cell then there are events like CellClick, CellDoubleClick, etc.
So, i wanna do same like as windows gridview with WPF DataGrid. I have searched so far but neither answer is applicable nor useful. Some of them says use the MouseDoubleClick event but, in this event, we have to check for each row as well as item in that row, so it is time consuming to check every cell for data and timing is most important here.
My DataGrid is bounded to DataTable and AutoGeneratedColumn is False. If your answer is based on AutoGeneratedColumn=True then it is not possible. Even, i 'm changing the styles of datagrid cell according to data, so there is no way to change AutoGeneratedColumn property.
A Cell Clicking/Double Clicking event should be as faster as windows grid's event. If it is possible then tell me how, and if not, then what is the alternative to do it?
Please Help Me.....
Thanks a lot....
I know this may be a little late to the party, but this might be useful to someone else down the road.
In your MyView.xaml:
<DataGrid x:Name="MyDataGrid" ...>
<DataGrid.Resources>
<Style TargetType="{x:Type DataGridCell}">
<EventSetter Event="MouseDoubleClick" Handler="DataGridCell_MouseDoubleClick"/>
</Style>
</DataGrid.Resources>
<!-- TODO: The rest of your DataGrid -->
</DataGrid>
In your MyView.xaml.cs:
private void DataGridCell_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
var dataGridCellTarget = (DataGridCell)sender;
// TODO: Your logic here
}
An alternative way would to be define a DataGridTemplateColumn instead of using the predefined columns like DataGridCheckBoxColumn, DataGridComboBoxColumn and then add an event handler to the UI element defined in the data template.
Below I have defined a MouseDown event handler for a TextBlock Cell.
<DataGrid AutoGenerateColumns="False">
<DataGrid.Columns>
<DataGridTemplateColumn>
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<TextBlock MouseDown="TextBlock_MouseDown"/>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
</DataGrid.Columns>
</DataGrid>
In the Code behind file:
private void TextBlock_MouseDown(object sender, MouseButtonEventArgs e)
{
TextBlock block = sender as TextBlock;
if (block != null)
{
// Some Logic
// block.Text
}
}
I know coding WPF is sometimes a PITA. Here you would have to handle the MouseDoubleClick event anyway. Then search the source object hierarchy to find a DataGridRow and do whatever with it.
UPDATE: Sample code
XAML
<dg:DataGrid MouseDoubleClick="OnDoubleClick" />
Code behind
private void OnDoubleClick(object sender, MouseButtonEventArgs e)
{
DependencyObject source = (DependencyObject) e.OriginalSource;
var row = GetDataGridRowObject(source);
if (row == null)
{
return;
}
else
{
// Do whatever with it
}
e.Handled = true;
}
private DataGridRow GetDataGridRowObject(DependencyObject source)
{
// Write your own code to recursively traverse up via the source
// until you find a DataGridRow object. Otherwise return null.
}
}
I have used something like this:
<DataGrid.InputBindings>
<MouseBinding Gesture="LeftDoubleClick" Command="{Binding ShowOverlay}" CommandParameter="{Binding Parameter}" />
</DataGrid.InputBindings>
And handle my commands in my View Model.
I'm trying to get a DataGridTemplateColumn to behave identically to a TextColumn
when the cell goes into edit mode (Press F2), the user can immediately start typing in the new value
by default, existing text content is selected - so that you can set new values easily
Got the first one done ; however selecting all the text isn't working. As mentioned by a number of posts, tried hooking into the GotFocus event and selecting all the text in code-behind. This worked for a standalone textbox ; however for a Textbox which is the edit control for a TemplateColumn, this doesn't work.
Any ideas?
Code Sample:
<Window.Resources>
<Style x:Key="HighlightTextBoxStyle" TargetType="{x:Type TextBox}">
<EventSetter Event="GotFocus" Handler="SelectAllText"/>
<EventSetter Event="GotMouseCapture" Handler="SelectAllText"/>
<Setter Property="Background" Value="AliceBlue"/>
</Style>
<DataTemplate x:Key="DefaultTitleTemplate">
<TextBlock Text="{Binding Title}"/>
</DataTemplate>
<DataTemplate x:Key="EditTitleTemplate">
<TextBox x:Name="Fox"
FocusManager.FocusedElement="{Binding RelativeSource={RelativeSource Self}}"
Text="{Binding Path=Title, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
Style="{StaticResource HighlightTextBoxStyle}">
</TextBox>
</DataTemplate>
</Window.Resources>
<DockPanel>
<TextBox DockPanel.Dock="Top" x:Name="Test" Text="{Binding Path=(FocusManager.FocusedElement).Name, ElementName=MyWindow}"
Style="{StaticResource HighlightTextBoxStyle}"/>
<toolkit:DataGrid ItemsSource="{Binding Items}" AutoGenerateColumns="False">
<toolkit:DataGrid.Columns>
<toolkit:DataGridTemplateColumn Header="Templated Title"
CellTemplate="{StaticResource DefaultTitleTemplate}"
CellEditingTemplate="{StaticResource EditTitleTemplate}" />
<toolkit:DataGridTextColumn Header="Title" Binding="{Binding Path=Title}" />
</toolkit:DataGrid.Columns>
</toolkit:DataGrid>
</DockPanel>
Missed updating the post with an answer...
The problem seems to be that for a custom data grid column (aka a DataGridTemplateColumn) the grid has no way of knowing the exact type of the editing control (which is specified via a DataTemplate and could be anything). For a DataGridTextColumn, the editing control type is known and hence the grid can find it and invoke a SelectAll() in it.
So to achieve the end-goal for a TemplateColumn, you need to provide an assist. I forgotten how I solved it the first time around.. but here is something that I searched-tweaked out today. Create a custom derivation of a TemplateColumn with an override of the PrepareCellForEdit method as shown below (Swap Textbox with your exact editing control).
public class MyCustomDataColumn : DataGridTemplateColumn
{
protected override object PrepareCellForEdit(FrameworkElement editingElement, RoutedEventArgs editingEventArgs)
{
var contentPresenter = editingElement as ContentPresenter;
var editingControl = FindVisualChild<TextBox>(contentPresenter);
if (editingControl == null)
return null;
editingControl.SelectAll();
return null;
}
private static childItem FindVisualChild<childItem>(DependencyObject obj)
}
Here's an implementation for FindVisualChild.
XAML:
<WPFTestBed:MyCustomDataColumn Header="CustomColumn"
CellTemplate="{StaticResource DefaultTitleTemplate}"
CellEditingTemplate="{StaticResource EditTitleTemplate}"/>
</DataGrid.Columns>
Lot of code for an annoying inconsistency.
I know this is way late but I took a different approach and creatively extended the TextBox class. I don't really like using the boolean to check if the text is already defined but the problem is that the selection events all fire before the text is set from the binding so SelectAll() doesn't have anything to select! This class is probably only useful as a editing template in something like a DataGridTemplateColumn. Every solution I found for this issue is pretty much a hack so I don't feel too bad about this one ... :)
class AutoSelectTextBox : TextBox
{
private bool _autoSelectAll= true;
protected override void OnInitialized(EventArgs e)
{
// This will cause the cursor to enter the text box ready to
// type even when there is no content.
Focus();
base.OnInitialized(e);
}
protected override OnKeyDown(System.Windows.Input.KeyEventArgs e)
{
// This is here to handle the case of an empty text box. If
// omitted then the first character would be auto selected when
// the user starts typing.
_autoSelectAll = false;
base.OnKeyDown(e);
}
protected override void OnTextChanged(TextChangedEventArgs e)
{
if (_autoSelectAll)
{
SelectAll();
Focus();
_autoSelectAll= false;
}
base.OnTextChanged(e);
}
}
Kinda VERY late...just putting this out here in case someone can use this
I had a similar need to DeSelect (or Select All) text in a DataGridTextColumn on editing
Just added the method to the PreparingCellForEdit event of the DataGrid
DataGrid.PreparingCellForEdit += DataGrid_PreparingCellForEdit;
Then assigned the (e.EditingElement as TextBox) and then set my options
private void DataGrid_PreparingCellForEdit(object sender, DataGridPreparingCellForEditEventArgs e)
{
var txtBox = e.EditingElement as TextBox;
txtBox.Select(txtBox.Text.Length, 0); //to DeSelect all and place cursor at end
txtBox.SelectAll(); // to selectall
}