I want to have a method fire when a button's enabled state changes, but it does not work. The method void EnableStartScan(bool isEnabled) in the view model never gets called.
<telerik:RadRibbonGroup Header="{x:Static res:StringTable.MachineCtrl}">
<telerik:RadRibbonButton x:Name="btnStart"
Text="{x:Static res:StringTable.Start}"
Size="Large"
LargeImage="/MCSP;component/Resources/Images/Button-Start.png">
<i:Interaction.Triggers>
<i:EventTrigger EventName="IsEnabledChanged">
<cal:ActionMessage MethodName="EnableStartScan">
<cal:Parameter Value="{Binding ElementName=btnStart, Path=IsEnabled}"/>
</cal:ActionMessage>
</i:EventTrigger>
</i:Interaction.Triggers>
</telerik:RadRibbonButton>
</<telerik:RadRibbonGroup>
Wy not control the state of your button in your ViewModel in the first place? Simply add a gate method in your viewModel and add trigger your other action within your viewModel
public bool CanSayHello(string name)
{
if(EvalIfEnable())
{
YourOtherMethod();
return true;
}
return false;
}
public void SayHello(string name)
{
ExecuteYourAction();
}
Related
I would like to do something when a click in a combobox, in a MVVM pattern.
I am trying to use input bindings in this way:
<ComboBox.InputBindings>
<KeyBinding Key="Return" Command="{Binding BuscarKeyDownCommand}"/>
<MouseBinding Gesture="LeftClick" Command="{Binding TiposFacturasMouseLeftClickCommand}"/>
</ComboBox.InputBindings>
In my view model I have this code:
private RelayCommand _tiposFacturasMouseLeftClickCommand;
public RelayCommand TiposFacturasMouseLeftClickCommand
{
get { return _tiposFacturasMouseLeftClickCommand ?? (_tiposFacturasMouseLeftClickCommand = new RelayCommand(param => TiposFacturasMouseLeftClick(), param => true)); }
}
private async void TiposFacturasMouseLeftClick()
{
try
{
//search for items.
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
}
But the command is not fired.
However, the key return input binding works as expected.
Which is the best way to bind the click event of the combobox? Or perhaps there are another better solution to search the items on the combobox the first time that I click on it.
Thanks.
You could install the Microsoft.Xaml.Behaviors.Wpf NuGet package and use an EventTrigger to invoke a command when an event is raised, e.g.:
<ComboBox xmlns:i="http://schemas.microsoft.com/xaml/behaviors">
<i:Interaction.Triggers>
<i:EventTrigger EventName="PreviewMouseLeftButtonDown" >
<i:InvokeCommandAction Command="{Binding TiposFacturasMouseLeftClickCommand}" />
</i:EventTrigger>
</i:Interaction.Triggers>
<ComboBoxItem>1</ComboBoxItem>
<ComboBoxItem>2</ComboBoxItem>
<ComboBoxItem>3</ComboBoxItem>
</ComboBox>
Please refer to this blog for more informatio about how to handle events in MVVM.
I have a DataGrid with long time loading.
I want put a BusyIndicator for the time to wait.
I have declared a property "IsBusy" in my ViewModel, the BusyIndicator is raised on it.
If I declare the property with "true" by default, the BusyIndicator does display good => OK.
If I declare it to be "false", the BusyIndicator is hidden => OK.
But, if I set the value by triggers in XAML, the property is well set, but the BusyIndicator doesn't appear.
ViewModel:
public bool IsBusy
{
get { return _IsBusy; }
set { _IsBusy = value; RaisePropertyChanged(nameof(IsBusy)); }
}
private void SetBusy(bool obj)
{
IsBusy = obj;
}
XAML:
<xctk:BusyIndicator Name="BusyBar" IsBusy="{Binding IsBusy, NotifyOnSourceUpdated=True, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" BusyContent="Traitement en cours. veuillez patienter..." />
<ComboBox x:Name="cbbSchEtt" ...>
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<i:InvokeCommandAction Command="{Binding SetBusyCommand}" CommandParameter="True"/>
<ei:CallMethodAction MethodName="LoadTableau" TargetObject="{Binding ElementName=ucTabBord}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</ComboBox>
Same thing if I set it by code behind (m is my ViewModel):
private void LoadTableau()
{
m.IsBusy = true;//Mouse.OverrideCursor = Cursors.Wait;
.....
m.IsBusy = false;
}
For information, if I don't set it to false at the end of LoadTableau(), the BusyIndicator is displayed well.
Any idea ?
Should I put all events in views code behind or there is a more proper way, like place commands in ViewModel?
For example, I want to open Tab on double click on the datagrid row, where should I handle this event?
No you should not put events in code behind. In MVVM (Model-View-ViewModel) design pattern, the view model is the component that is responsible for handling the application's presentation logic and state. This means that your view's code-behind file should contain no code to handle events that are raised from any user interface (UI) element.
for eg if you have button in your xaml
<Button Content="OK" Click="btn_Click"/>
protected void btn_Click(object sender, RoutedEventArgs e)
{
/* This is not MVVM! */
}
Instead you can use WPF Command.All you have to do is bind to its Execute and CanExecute delegates and invoke your command.
So your code will now be
public class ViewModel
{
private readonly DelegateCommand<string> _clickCommand;
public ViewModel()
{
_clickCommand = new DelegateCommand(
(s) => { /* perform some action */ }, //Execute
null
} //CanExecute );
public DelegateCommand ButtonClickCommand
{
get { return _clickCommand; }
}
}
<Button Content="COOL" Command="ButtonClickCommand"/>
Kyle is correct in that your handlers should appear in the view model. If a command property doesn't exist then you can use an interaction trigger instead:
<DataGrid>
<i:Interaction.Triggers>
<i:EventTrigger EventName="MouseDoubleClick">
<i:InvokeCommandAction Command="{Binding Mode=OneWay, Path=OpenClientCommand}" CommandParameter="{Binding ElementName=searchResults, Path=SelectedItems}" />
</i:EventTrigger>
</i:Interaction.Triggers>
... other stuff goes here ...
</DataGrid>
Or you can use MVVM Lite's EventToCommand, which also allows you to pass in the message parameters:
<i:Interaction.Triggers>
<i:EventTrigger EventName="Closing">
<cmd:EventToCommand Command="{Binding ClosingCommand}" PassEventArgsToCommand="True" />
</i:EventTrigger>
</i:Interaction.Triggers>
Which is used in in this case to cancel the window close event in response to the "Are you sure you want to quit?" dialog:
public ICommand ClosingCommand { get { return new RelayCommand<CancelEventArgs>(OnClosing); } }
private void OnClosing(CancelEventArgs args)
{
if (UserCancelsClose())
args.Cancel = true;
}
Relevant namespaces are as follows:
xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
xmlns:cmd ="http://www.galasoft.ch/mvvmlight"
I am new to wpf and interactivity. I am trying to execute a command based on some event trigger. In the code below, when the doubleclick event is trigger, CanExecute is invoked and return false but the execute function is still called. Is this the default behavior for invokecommandaction? I would think that when can execute returns false, execute will not be called.
<UserControl x:Class="..."
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity">
<i:Interaction.Triggers>
<i:EventTrigger EventName="MouseDoubleClick">
<i:InvokeCommandAction Command="{Binding Path=DisplayReportCommand}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
...
Yes it will use the canexecute and command will not be execute if it return false. I have posted a code example.
Here is the command in your ViewModel class
RelayCommand _showMessageCommand;
public ICommand ShowMessageCommand
{
get
{
if (_showMessageCommand == null)
{
_showMessageCommand = new RelayCommand(param => this.ShowMessage(), param => this.CanShowMessage);
}
return _showMessageCommand;
}
}
public void ShowMessage()
{
MessageBox.Show("Nitesh");
}
private bool CanShowMessage
{
get
{
return false; // Set to true to execute the command
}
}
and this is how you will use it in XAML
<Button Content="Nitesh">
<i:Interaction.Triggers>
<i:EventTrigger EventName="MouseDoubleClick">
<i:InvokeCommandAction Command="{Binding ShowMessageCommand}" ></i:InvokeCommandAction>
</i:EventTrigger>
</i:Interaction.Triggers>
</Button>
I'm developing a WPF project from MVVM way.
I bound Observable Collection to a XamTabControl. And if I add a new item to the Observable Collection a new tab is generated. But if I close the tab, the tab item is not removed from the Observable Collection.
I can do this manually if i can trigger the Closing Event (or Closed Event) for the tab. But those two events are not fired. But some event are fired such as MouseUp.
<igWindows:XamTabControl
Height="198"
HorizontalAlignment="Left"
Margin="0,54,0,0"
ItemsSource="{Binding Tabs}"
SelectedItem="{Binding SelectedTab}"
Name="xamTabControl1"
VerticalAlignment="Top"
Width="651">
<i:Interaction.Triggers>
<i:EventTrigger EventName="Closing">
<i:InvokeCommandAction Command="{Binding TabCloseCommand}" />
</i:EventTrigger>
</i:Interaction.Triggers>
<igWindows:XamTabControl.ItemContainerStyle>
<Style TargetType="igWindows:TabItemEx">
<Setter Property="Header" Value="{Binding Header}"/>
<Setter Property="CloseButtonVisibility" Value="{Binding CloseButtonVisibility}"/>
</Style>
</igWindows:XamTabControl.ItemContainerStyle>
<igWindows:XamTabControl.ContentTemplate>
<!-- this is the body of the TabItem template-->
<DataTemplate>
<TextBlock Text="{Binding Content}" />
</DataTemplate>
</igWindows:XamTabControl.ContentTemplate>
</igWindows:XamTabControl>
And this is my View Model
private ObservableCollection<TabItem> tabs;
private TabItem selectedTab;
private ICommand tabCloseCommand;
public ObservableCollection<TabItem> Tabs
{
get
{
return tabs;
}
set
{
tabs = value;
NotifyPropertyChanged("Tabs");
}
}
public TabItem SelectedTab
{
get
{
return selectedTab;
}
set
{
selectedTab = value;
NotifyPropertyChanged("SelectedTab");
}
}
public ICommand TabCloseCommand
{
get
{
if (tabCloseCommand == null)
{
tabCloseCommand = new RelayCommand(param => this.CloseTab(), null);
}
return tabCloseCommand;
}
}
private void CloseTab()
{
}
It's probably because the DataContext for the object that runs the Closing event is your TabItem class, and not the class that contains the TabCloseCommand
Use ElementName or RelativeSource to set the Source of your command binding to the TabControl.DataContext first, and it should work
<i:InvokeCommandAction Command="{Binding ElementName=xamTabControl1,
Path=DataContext.TabCloseCommand}" />
The code that you have to wire up the closing event doesn't work because there is no Closing or Closed event on the XamTabControl and that is the associated object. I am not sure if it is possible to use the EventTrigger to attach to an event of the TabItemEx from the xamTabControl. If you were to add a handler to the XamTabControl without the EventTrigger, you would do the following:
<igWindows:XamTabControl
Name="xamTabControl1"
AllowTabClosing="True"
igWindows:TabItemEx.Closed="OnTabClosed">
</igWindows:XamTabControl>
You can also see a detailed example in the Removing a Closed Tab topic in the help.