I have an application which is having TextBox. Upon getting the focus, I need to show the Calendar as Popup.
My question is how to show subscribe the GotFocus event and show the calendar through view model?
It is fairly acceptable to write code-behind for view-specific tasks like this one, however if you insist to have clean code-behind files , do the following
you will need MvvmLight.Extras.WPF4.dll and System.Windows.Interactivity.dll, the second DLL comes mainly with blend , google the first and at any case you can find them both on the MVVMLight package.
reference them as follows:
xmlns:cmd="clr-namespace:GalaSoft.MvvmLight.Command;assembly=GalaSoft.MvvmLight.Extras.WPF4"
xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
see your textBox
<TextBox>
<i:Interaction.Triggers>
<i:EventTrigger EventName="GotFocus">
<cmd:EventToCommand Command="{Binding showCalendar, Mode=OneWay}" MustToggleIsEnabledValue="True"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</TextBox>
on your view model you should have a property that is bound to your Calendar Visibility property , change it to Visible inside the method invoked by the command.
You really don't need to go to the ViewModel for this - it can be done very simply in XAML. Use a BooleanToVisibilityConverter on a binding that is attached to the TextBox's IsFocused property.
<TextBox x:Name="_textBox" Text="{Binding Text}" />
<myNameSpace:Calendar Visibility="{Binding ElementName=_textBox, Path=IsFocused, Converter={x:Static _boolToVisibilityConverter}, Mode=OneWay}" />
Related
What I want is for a datagrid to appear under a textbox when the user starts. Once focus is lost from the textbox the datagrid disappears. I am having a hard time format it so does not screw up the rest of the windows formatting.
Before you ask about using a list box, I need multiple columns and the user should be able to reorder the list.
One more idea. Bind the visibility of the DataGrid to a property from your ViewModel. Initially you can set the Visibility to Visible.
Next you can use the Interactivity on the textbox's LostFocus event to change the Visibility to Hidden/Collapsed.
The following is an example
<TextBox Text="Test">
<i:Interaction.Triggers>
<i:EventTrigger EventName="LostFocus">
<i:InvokeCommandAction Command="{Binding DataGridVisibilityCommand}" CommandParameter="Collapsed"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</TextBox>
<DataGrid Visibility="{Binding DataGridVisibility}"/>
add the namespace
xmlns:i="http://schemas.microsoft.com/expression/2010/interactions"
to your window/usercontrol and add the necessary dll references.
I am using System.Windows.Interactivity.dll and Microsoft.Expression.Interaction.dll to do event handling in Viewmodel in my MVVM WPF project.
below is the code inside my Xaml:
<ItemsControl ItemsSource="{Binding Path= HeaderList}" Grid.Row="0" Grid.Column="0" >
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Text}" Width="100" HorizontalAlignment="Left" >
<i:Interaction.Triggers>
<i:EventTrigger EventName="PreviewMouseLeftButtonDown">
<ie:CallMethodAction MethodName="PrevMouseDownEventHandler" TargetObject="{Binding}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</TextBlock>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
for this I added namespaces in the same Xaml.
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
xmlns:ie="http://schemas.microsoft.com/expression/2010/interactions"
and in my viewmodel I have created a method having PrevMouseDownEventHandler name which is same as that of I mentioned as CallMethod inside EventTigger in the Xaml.
On running my application when I presses mouse button on TextBlock event is generated and look for PrevMouseDownEventHandler method and leave me into following exception:
Could not find method named 'PrevMouseDownEventHandler' on object of type 'string' that matches the expected signature.
this method is as below in my ViewModel.
public void PrevMouseMoveEventHandler(object sender, MouseButtonEventArgs e)
{
// Some implementation here;
}
I don't have any idea where I am going wrong.
Except this all the functionalities inside Viewmodel is working fine for me.
what would be possible solution for this?
CallMethodAction is a delegate with no parameters and no return value. So the "handler" (really an action trigger) would have to look like this:
public void PrevMouseMoveEventHandler()
{
// Some implementation here;
}
Also, you'll need to bind to the View Model (your current binding points to the current item in the ItemsControl). You could do this using RelativeSource binding:
<ie:CallMethodAction MethodName="PrevMouseDownEventHandler"
TargetObject="{Binding Path=DataContext,RelativeSource={RelativeSource AncestorType=ItemsControl}" />
It is looking for the method on the String object you have bound your Text property to.
Basically your data context has changed from the view model to a property of the View Model.
I'm working on a WPF application and I'm using the MVVM pattern. I use MVVMLight to help me handle some Events. I need to forward the "Click" event so that I can pass the arguments as well so that I can know for sure which item that sent the event. If I use the "Command" I cant know for sure that it was the selected item that sent the event - as the item doesnt need to be selected to right click on it.
This is my code for displaying a list of "order lines". There are two types of order lines, and for one of the data types; "AccessoryOrderLine" - I want to add a context menu.
My problem is that I cannot access my Window's DataContext. I've named the root node in the Window "root", and I'm trying to access the root's DataContext, but this failes with the following error:
System.Windows.Data Error: 4 : Cannot find source for binding with
reference 'ElementName=root'.
BindingExpression:Path=DataContext.PackAccessory; DataItem=null;
target element is 'EventToCommand' (HashCode=5903270); target property
is 'Command' (type 'ICommand')
<ListBox HorizontalContentAlignment="Stretch" Margin="10,0,10,10" DockPanel.Dock="Bottom" Grid.Row="1" ItemsSource="{Binding OrderLines, NotifyOnSourceUpdated=True, NotifyOnTargetUpdated=True, UpdateSourceTrigger=PropertyChanged}">
<ListBox.Resources>
<DataTemplate DataType="{x:Type m:UnitOrderLine}">
<v:OrderLine />
</DataTemplate>
<DataTemplate DataType="{x:Type m:AccessoryOrderLine}">
<v:OrderLine>
<v:OrderLine.ContextMenu>
<ContextMenu>
<MenuItem Header="Pack 1" IsCheckable="False">
<i:Interaction.Triggers>
<i:EventTrigger EventName="Click">
<cmd:EventToCommand Command="{Binding ElementName=root, Path=DataContext.PackAccessory }" PassEventArgsToCommand="True" />
</i:EventTrigger>
</i:Interaction.Triggers>
</MenuItem>
</ContextMenu>
</v:OrderLine.ContextMenu>
</v:OrderLine>
</DataTemplate>
</ListBox.Resources>
</ListBox>
I've also tried to use "TemplatedParent" and then I get access to my "OrderLine" DataContext, but I cant get one step further back to my "MainWindowModel".
http://www.thomaslevesque.com/2011/03/21/wpf-how-to-bind-to-data-when-the-datacontext-is-not-inherited/
Found a solution to my problem :)
Found a solution. Updated my original post with the link to my solution.
Its not issue with the DataTemplate. Binding with ElemetName works in all cases except in the case of ContextMenu since it does not lies in the same visual tree as of your window. However, there is one hack where you can use the PlacementTarget property of your context menu.
For details refer to this link - http://social.msdn.microsoft.com/Forums/nl/wpf/thread/526ab350-8788-4bc6-a98a-1e4dee6ad33a
It contains exactly what you are trying to achieve here.
Seems like here are answers for your question:
ElementName Binding from MenuItem in
ContextMenu
WPF MenuItem.Command binding to
ElementName..
The MVVMLight EventToCommand can be used to fire an ICommand on your viewmodel quite easily.
<DataGrid>
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<GalaSoft_MvvmLight_Command:EventToCommand
Command="{Binding ProductSelectionChangedCommand, Mode=OneWay} "
CommandParameter="{Binding SelectedItems, ElementName=gridProducts}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</DataGrid>
In this instance the SelectionChanged event belongs to DataGrid, and the Interaction.Triggers xaml is nested directly inside DataGrid.
I cannot figure out how to do the same when the event is a DataGridRow (which has its own events for each row).
I managed to do this, but it involves a handler function which I'd like to avoid :
<DataGrid>
<DataGrid.ItemContainerStyle>
<Style TargetType="DataGridRow">
<EventSetter Event="DataGridRow.MouseEnter"
Handler="Row_MouseEnter"/>
</Style>
</DataGrid.ItemContainerStyle>
</DataGrid>
In the Row_MouseEnter event (on my .xaml.cs file) I just 'find the command' on the ViewModel and trigger it programatically.
I'd really like to know if there's a way of doing the same directly with Interaction.Triggers
(FYI: What I'm doing is I have a panel above the grid which displays details of the row that the mouse is over before clicking on it - which triggers a detail view).
Yeah you can directly bind to the command in your ViewModel by creating your own custom behaviour class and using it in xaml file. These links might get you started - Binding using interactivity and Binding through interaction in MVVM
I have a Treeview in a Silverlight 4 project, and I want to bind to its SelectedItem. When I do a binding to SelectedItem (Mode=TwoWay) its throwing an error in blend because SelectedItem is readonly, which is causing my XAML to not render. I don't ever want to SET the SelectedItem property, I just want to know when it changes via UI interaction. In WPF, I would just bind its SelectedItem using Mode=OneWayToSource, but Silverlight does not support that mode (afaik).
Treeview :
<controls:TreeView ItemsSource="{Binding Repository.MajorClasses}" SelectedItem="{Binding SelectedItem, Mode=TwoWay}" />
Is there a workaround that anyone has used? And anyone know why OneWayToSource is omitted from Silverlight?
It's really readonly, so you cann't do that. You can use TreeView as base control and create CustomTreeView with implementation of bindable SelectedItem. Or create own behavior(attached property). Or use some third party control (f.i. telerik).
If you just want your VM to be informed when the user changes the selection, you should be able to do exactly what you are doing (a two way binding).
I have this working in Visual studio so, I suggest trying it from there, might just be a problem with Blend. VS intellisense doesn't suggest SelectedItem when typing in the XAML editor but that doesn't stop it from working.
The bound property in your VM is definately of the right type (MajorClass by the looks of it)?
What you need to do is make use of an Interaction Trigger and bind it to the SelectedItemChangedevent as follows:
<sdk:TreeView x:Name="ModuleNavigationItemWrappersTreeView" ItemsSource="{Binding ModuleNavigationItemWrappers}">
<sdk:TreeView.ItemTemplate>
<sdk:HierarchicalDataTemplate ItemsSource="{Binding Children}">
<StackPanel Orientation="Horizontal" Margin="0,2,0,2">
<Image Source="/VanguardFinancials.Common;component/Images/icons/flag_blue.png" />
<TextBlock Margin="2,0,0,0" Text="{Binding ItemDescription}"></TextBlock>
</StackPanel>
</sdk:HierarchicalDataTemplate>
</sdk:TreeView.ItemTemplate>
<interactivity:Interaction.Triggers>
<interactivity:EventTrigger EventName="SelectedItemChanged">
<interactivity:InvokeCommandAction Command="{Binding TrackSelectedModuleNavigationItemWrapper}" CommandParameter="{Binding ElementName=ModuleNavigationItemWrappersTreeView}" />
</interactivity:EventTrigger>
</interactivity:Interaction.Triggers>
</sdk:TreeView>
Visit this for more information about Behaviors and Triggers. Hope this helps.