The WPF ListView class can be set up to automatically handle scrolling without an external ScrollViewer and it's possible to register an event handler for the control's internal scrollbar by writing XAML like such:
<ListView ScrollViewer.ScrollChanged="ScrollChanged" />
How to attach it to MVVM light Command? I tried the following, but it doesn't work:
<ListView>
<i:Interaction.Triggers>
<i:EventTrigger EventName="ScrollViewer.ScrollChangedEvent">
<cmd:EventToCommand Command="{Binding ScrollCommand}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</ListView>
Note: ScrollCommand - is a RelayCommand from my viewmodel.
EventTrigger doesn't trigger for routed events. You can use the solution proposed in this article
to create a RoutedEventTrigger class and use it instead of EventTrigger.
I recommend a Behavior for this. If you don't have Blend, you'll need to get the Blend SDK. But once you have that, you can follow this tutorial to extend the behavior of the ScrollViewer.
Related
How can I let my controls on the window know that their states should be changed. I have to use ICommand and since controls can have different states (Enable/Disable , Checked/Unchecked ...) have to handle them with VisualStateManager.
This could be a possible scenario:
When Record button is clicked(Checked) the other controls in the window should be uncheckable and once the recording is finished they should be checkable and many other scenarios.
Any help would be really appreciated.
Thanks.
You can achieve it with the help of interaction and interactivity. See if it helps.
Add below references in your XAML
xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
You can bind your ICommand and provide a VisualState name that will be applied when Button is clicked
<Button>
<i:Interaction.Triggers>
<i:EventTrigger EventName="Click">
<i:InvokeCommandAction Command="{Binding YourICommand}" />
<ei:GoToStateAction StateName="YourVisualStateName" />
</i:EventTrigger>
</i:Interaction.Triggers>
</Button>
If you don't have Blend 4, you can install the Blend 4 SDK to get the current behavior assemblies.
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 slider control in view i need to call the ValueChanged event of slider and update one property in model based on that. how i can implement this using MVVM pattern.
where I have to write the ValueChanged event? how i can connect ValueChanged event code with view?
i just take the answer from here cause i use it in my projects too:
You should use an EventTrigger in combination with InvokeCommandAction from the Windows.Interactivity namespace. Here is an example:
xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<i:InvokeCommandAction Command="{Binding SelectedItemChangedCommand}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
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}" />
I have a WPF 3.5 app built using MVVM pattern. I have a tabcontrol and I want to excecute an ICommand on the view model when the user clicks a certain tab (jn my case the "Preview" tab).
How do I hook up my ICommand to the tabitem or tabcontrol using just the XAML? I am using MVVM so I dont want to use events and get filthy, dirty code in the code-behind.
I think Im missing something simple here!
Thanks,P
Please refer this article : hooking up commands to events
Or you can use this approach
You should use InvokeCommandAction, Looks like this:
<TabItem Header="TabItem">
<i:Interaction.Triggers>
<i:EventTrigger EventName="MouseLeftButtonDown">
<i:InvokeCommandAction Command="SomeCommand"/>
</i:EventTrigger>
</i:Interaction.Triggers>
<Grid />
</TabItem>
Be sure to include the xmlns in the top:
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
and of course to reference System.Windows.Interactivity (new in WPF4)