Have a little problem with hooking up the keydown event without codebehind!
So, we have the combobox
<ComboBox Height="20" Width="auto"
ItemsSource="{Binding AlignComboItems}"
SelectedValue="{Binding SelectedComboItem, Mode=TwoWay}"
SelectedValuePath="Key" DisplayMemberPath="Value"
SelectedItem="{Binding SelectedItem}"
x:Name="cmbBoxAlign">
</ComboBox>
and some TextBox.
<TextBox Text={Binding SomeSource}></TextBox>
How to catch the keydown event on the TextBox for selecting the (for example) the last element in ComboBox? I cant use the TextBox DataSource property changing, because need hook the user input up.
If you don't mind installing the Expression Blend SDK you should be able to do this in your textbox
<i:Interaction.Triggers>
<i:EventTrigger EventName="KeyUp">
<i:InvokeCommandAction Command="{Binding Path=TheCommand}" />
</i:EventTrigger>
</i:Interaction.Triggers>
After adding a reference to System.Windows.Interactivity and the following namespace in your xaml
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
Link to the Expression SDK for 4.0
http://www.microsoft.com/en-us/download/details.aspx?id=10801
If you want to have code fire in your view model every time there is a key down in the text box you need to change the binding slightly:
<TextBox Text="{Binding SomeSource, UpdateSourceTrigger=PropertyChanged}"
Then in the view model the setter will be called:
private string _someSource;
public string SomeSource{
get { return _someSource; }
set {
//this will fire on key down
_someSource= value;
//based off the value you can set SelectedComboItem accordingly
OnPropertyChanged( "SomeSource" );
}
}
Also, make sure you have INotifyPropertyChanged set up on your view model.
Related
In my project I have a "Generate Reports" Button and a "Select Location" ComboBox. I want the user to be unable to choose a location before clicking
"Generate Report" Button.
the xaml containing the combobox and the button:
<Button Content="Generate Reports" Command="{Binding GenerateReportsCommand}" Height="36" Margin="4" />
<ComboBox Grid.Column="2" ItemsSource="{Binding Locations}" SelectedItem="{Binding SelectedLocation}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<i:InvokeCommandAction Command="{Binding LocationFilterCommand}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</ComboBox>
What can I do in the ViewModel or UI? Thank you for all your helps.
I'm going to assume you know how to use data binding (based on your post you already use it).
Create a new Boolean in your ViewModel and bind the ComboBox's IsEnabled to it. (Something like IsEnabled="{Binding YOURBOOLEAN}")
Update that Boolean from your GenerateReportsCommand after the user successfully generated the report. If you set that variable to true, the ComboBox's IsEnabled will also be set to true.
You should have an additional property inside the ViewModel.
private bool _areReportsGenerated = false;
public bool AreReportsGenerated
{
get => _areReportsGenerated;
set
{
_areReportsGenerated = value;
OnPropertyChanged(); // you method's implementation of INotifyPropertyChanged
}
}
If you don't have an implementation of INotifyPropertyChanged you can take a look at Microsoft one.
Inside GenerateReportsCommand you should set AreReportsGenerated to true.
In the xaml then you only have to bind the newly created property to the IsEnabled property of the ComboBox
<ComboBox Grid.Column="2" ItemsSource="{Binding Locations}" SelectedItem="{Binding SelectedLocation}" IsEnabled="{Binding AreReportsGenerated}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<i:InvokeCommandAction Command="{Binding LocationFilterCommand}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</ComboBox>
It should work.
I hope I was helpful.
I've got a ListView with some KeyBindings that let the user move and delete entries with keyboard shortcuts. However, I don't want the bindings to be accessible all the time.
The button controls to add, remove, and move entries have their visibility tied to the selection of a ComboBox (only certain users can edit). I want the keyboard shortcuts to deactivate based on the box selection as well.
I haven't been able to find any info on whether or not this is possible yet. What do you guys think?
<ComboBox x:Name="TesterIdentityBox" ItemsSource="{Binding Path=TesterIdentityList, UpdateSourceTrigger=PropertyChanged}" DisplayMemberPath="Name" SelectedItem="{Binding Path=TesterIdentitySelection, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" SelectedIndex="{Binding TesterIdentityIndex, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
<ListView ItemsSource="{Binding TestViewList, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" SelectedIndex="{Binding SelectedTestIndex, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" SelectedItem="{Binding Path=SelectedTest}">
<ListView.InputBindings>
<KeyBinding Key="Up" Command="{Binding Path=MoveTestUpCommand}" CommandParameter="{Binding Path=SelectedTest.Description}" />
<KeyBinding Key="Down" Command="{Binding Path=MoveTestDownCommand}" CommandParameter="{Binding Path=SelectedTest.Description}" />
<KeyBinding Key="Delete" Command="{Binding Path=RemoveTestCommand}" />
</ListView.InputBindings>
I used Style Setters with DataTriggers to alter the command buttons' visibility, but I don't know what (if anything) is the equivalent for a non-visual element like a KeyBinding.
The simplest way in this case would be to implement the CanExecute() methods in your MoveTestUpCommand, MoveTestDownCommand and RemoveTestCommand. This methods should return false when you don't want the user to be able to do those things. So, your KeyBindings will have no effect since the commands will not be executed.
If your buttons' Command properties are also bound to these commands, these buttons will then update their availability (IsEnabled property) automagically according to the CanExecute() return values. To update the view state from the viewmodel, simply call the RaiseCanExecuteChanged() methods on corresponding commands (this depends on your ICommand implementation however).
To set the button's visibility according to its availability, you could use something like:
<Button
Command = "{Binding SampleCommand}"
Visibility = "{Binding IsEnabled, RelativeSource = {RelativeSource Self}, Converter = {StaticResource BooleanToVisibilityConverter}}"/>
There is an implementation of the BooleanToVisibilityConverter in System.Windows.Controls.
I have a ComboBox:
<ComboBox x:Name="cbConnection"
ItemsSource="{Binding Source={StaticResource XmlConnectionList}, XPath=//ComboItem}"
DisplayMemberPath="Key"
SelectedValuePath="Value"
SelectedValue="{Binding Path=ConnectionString,ValidatesOnDataErrors=True,UpdateSourceTrigger=PropertyChanged}"
Margin="{StaticResource ConsistentMargins}"
Validation.ErrorTemplate="{StaticResource TextBoxErrorTemplate}" Width="120"
LostFocus="{Binding Path=cbConnection_LostFocus}"/>
I am trying to get the LostFocus event handler moved to the ViewModel because I do some error handling within the setter for the SelectedValue binding "ConnectionString" found in the ViewModel. I want this to happen if a user reselects the same ComboBoxItem, which does fire OnPropertyChanged unless a different list item is selected.
The above binding results in error
A 'Binding' cannot be set on the 'AddLostFocusHandler' property of
type 'ComboBox'. A 'Binding' can only be set on a DependencyProperty
of a DependencyObject.
How can I fire repeatable code within the ViewModel on selection of any item within a ComboBox, regardless of the user's selection?
You'll need to include a reference to the System.Windows.Interactivity dll, but it will look something like this:
xmlns:b="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
<ComboBox>
<b:Interaction.Triggers>
<b:EventTrigger EventName="LostFocus">
<b:InvokeCommandAction Command="{Binding cbConnection_LostFocus}" CommandParameter="{Binding}"/>
</b:EventTrigger>
</b:Interaction.Triggers>
</ComboBox>
Josh's answer worked for me with a different namespace:
xmlns:b="http://schemas.microsoft.com/expression/2010/interactivity"
<ComboBox>
<b:Interaction.Triggers>
<b:EventTrigger EventName="LostFocus">
<b:InvokeCommandAction Command="{Binding cbConnection_LostFocus}" CommandParameter="{Binding}"/>
</b:EventTrigger>
</b:Interaction.Triggers>
</ComboBox>
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.
So let's say I have an MVVM application and I want the user to fill out a TextBox and while he is filling it out, I want to check to see if he has typed in the last name of a customer yet.
Here is how I get my ViewModel to know when the user has changed the item in the ComboBox:
<ComboBox
ItemsSource="{Binding Customers}"
ItemTemplate="{StaticResource CustomerComboBoxTemplate}"
Margin="20"
HorizontalAlignment="Left"
SelectedItem="{Binding SelectedCustomer, Mode=TwoWay}"/>
And here is how I get my ViewModel to know when the user has moved the Slider:
<Slider Minimum="0"
Margin="10"
Width="400"
IsSnapToTickEnabled="True"
Maximum="{Binding HighestCustomerIndex, Mode=TwoWay}"
Value="{Binding SelectedCustomerIndex, Mode=TwoWay}"/>
And here is how I get my ViewModel to know when the user has changed text in the TextBox and moved the focus away from the TextBox:
<TextBox
Width="200"
Text="{Binding TypedCustomerName}"/>
But how do I get my ViewModel to know when the user has changed text in the TextBox as he types, e.g. something like this:
PSEUDO-CODE (causes error since TextChanged is an event):
<TextBox
Width="200"
TextChanged="{Binding CurrentTextInTextBox}"/>
If you like, instead of only updating the ViewModel when the TextBox has lost focus, you can set it to update as they type. The UpdateSourceTrigger on the Text binding property of a TextBox is set to LostFocus by default instead of PropertyChanged like most other controls, however you can set it explicitly in the binding. By doing so, the TypedCustomerName property in the VM or M will update as it is changed in the UI.
<TextBox
Width="200"
Text="{Binding TypedCustomerName, UpdateSourceTrigger=PropertyChanged}"/>
If that's not what you're looking for, you could also use AttachedCommandBehaviors to bind the TextChanged routed event to an ICommand that exists in your View Model.
TextBoxex default is to update on LostFocus. Set UpdateSourceTrigger="PropertyChanged" to update as user is typing.