In WPF data binding, I can bind the IsChecked property to some data, e.g. user setting, but I need to handle "CheckChanged" event, I know I can seperately handle Checked, Unchecked event, but is there any way to get notified when this value is changed?
<CheckBox Content="Case Sensitive" IsChecked="{Binding bSearchCaseSensitive,
Source={x:Static Properties:Settings.Default}}" />
Note: I don't care if it is checked or unchecked. I just want to be notified when it is changed.
That you can handle the checked and unchecked events seperately doesn't mean you have to. If you don't want to follow the MVVM pattern you can simply attach the same handler to both events and you have your change signal:
<CheckBox Checked="CheckBoxChanged" Unchecked="CheckBoxChanged"/>
and in Code-behind;
private void CheckBoxChanged(object sender, RoutedEventArgs e)
{
MessageBox.Show("Eureka, it changed!");
}
Please note that WPF strongly encourages the MVVM pattern utilizing INotifyPropertyChanged and/or DependencyProperties for a reason. This is something that works, not something I would like to encourage as good programming habit.
As a checkbox click = a checkbox change the following will also work:
<CheckBox Click="CheckBox_Click" />
private void CheckBox_Click(object sender, RoutedEventArgs e)
{
// ... do some stuff
}
It has the additional advantage of working when IsThreeState="True" whereas just handling Checked and Unchecked does not.
Im putting this in an answer because it's too long for a comment:
If you need the VM to be aware when the CheckBox is changed, you should really bind the CheckBox to the VM, and not a static value:
public class ViewModel
{
private bool _caseSensitive;
public bool CaseSensitive
{
get { return _caseSensitive; }
set
{
_caseSensitive = value;
NotifyPropertyChange(() => CaseSensitive);
Settings.Default.bSearchCaseSensitive = value;
}
}
}
XAML:
<CheckBox Content="Case Sensitive" IsChecked="{Binding CaseSensitive}"/>
I know this is an old question, but how about just binding to Command if using MVVM?
ex:
<CheckBox Content="Case Sensitive" Command="{Binding bSearchCaseSensitive}"/>
For me it triggers on both Check and Uncheck.
A simple and proper way I've found to Handle Checked/Unchecked events using MVVM pattern is the Following, with Caliburn.Micro :
<CheckBox IsChecked="{Binding IsCheckedBooleanProperty}" Content="{DynamicResource DisplayContent}" cal:Message.Attach="[Event Checked] = [Action CheckBoxClicked()]; [Event Unchecked] = [Action CheckBoxClicked()]" />
And implement a Method CheckBoxClicked() in the ViewModel, to do stuff you want.
What about the Checked event? Combine that with AttachedCommandBehaviors or something similar, and a DelegateCommand to get a function fired in your viewmodel everytime that event is called.
Related
I have a silverlight application. One of StackPanel will display the table. The first column is a check box.
<telerik:RadGridView.Columns>
<telerik:GridViewColumn Width="80" Header="Complete" HeaderTextAlignment="Center" TextAlignment="Center">
<telerik:GridViewColumn.CellTemplate>
<DataTemplate>
<CheckBox HorizontalAlignment="Center" IsChecked="{Binding Something, Converter={StaticResource ShortToBooleanConverter}}" Checked="Complete_Checked"></CheckBox>
</DataTemplate>
</telerik:GridViewColumn.CellTemplate>
</telerik:GridViewColumn>
What I want is that once I click the box, a message box with Y/N pops up. I do have a Complete_Checked method in MVVM. But I get the error
Event handler 'Complete_Checked` not found on class.....
You can't use click event handlers with MVVM you need to use CommandBinding or DataBinding depending on what you're doing.
With your example you'll use data binding. You want to bind to the checkbox dependency property called IsChecked. You'll also want to use the Mode of TwoWay. This will allow the UI to update the bound property when it changes.
<CheckBox IsChecked="{Binding CheckBoxIsChecked, Mode=TwoWay}">
Then in your object model not viewmodel
private bool _checkBoxIsChecked;
public bool CheckBoxIsChecked
{
get{ return _checkBoxIsChecked;}
set{_checkBoxIsChecked = value; OnPropertyChanged("CheckBoxIsChecked"); }
}
Hello im new to making apps with WPF and XAML in Visual Studio. So I have a grid I want to change its properties in the code.
My Grid's properties:
<Grid HorizontalAlignment="Left"
Height="603"
Margin="0,51,0,0"
x:Name="usersPan"
VerticalAlignment="Top"
Width="1286">
How I have been trying to change its properties
this.usersPan.SetValue(Grid.WidthProperty, PAN_SIZE);
usersPan.SetValue(Grid.WidthProperty, PAN_SIZE);
usersPan.Width = 0;
usersPan.Visibility = Visibility.Collapsed;
When I try to do that^ it says null reference for userPan
Thanks
Noooooooo, Don't ever do that. Make a ViewModel that is bound to the Grid's Width property, and then just change the value.
My suspicion is that you do not need this at all. Have a look into containers, and how to position them.
In all of this years, there have been rare occasions I needed to do that and I suspect you do not need to. Tell me what you are doing.
EDIT:
You have a VM which needs to implement the NotifyPropertyChanged interface (I won't do that here, there are plenty of examples on hoew to do that)
public class MainVM
{
public ObservableCollection<TabVM> TabsVms {get;set;}
public int SelectedIndex {get;set}
}
bound to the control
<TabControl DataContext={TabsVMs} SelectedIndex="{Binding SelectedIndex}">
...
</TabControl>
And in runtime you create a couple of Tabs
var TabsVMs = new ObservableCollection<TabVM>();
TabsVMs.add(new TabVM());
TabsVMs.add(new TabVM());
TabsVMs.add(new TabVM());
Then in runtime you change the value of the index.
MainVm.SelectedIndex = 1
and the the coresponding tab will become selected.
EDIT:
I can also recommend you to use Fody for the MVVM notification.
Also, when it comes to bindings, I can recommend you to use WPF inspector. a handy little tool
The best way to write WPF programs is to use the MVVM (Model-View-View Model) design pattern. There are two (2) ideas behind MVVM:
Write as little code as possible in the view's code-behind and put all of the logic in the View Model object, using WPF's data binding feature to connect the properties of the View Model object to the view's controls.
Separate the logic from the display so you can replace the view with some other construct without having to change the logic.
MVVM is a huge topic on its own. There are lots of articles about it, and frameworks that you can use to build your program. Check out MVVM Light, for example.
Don't know exactly why Grid is invisible in code-behind, but You can access it's properties using events (but don't think it is perfect solution).
For example add to your grid event Loaded
<Grid HorizontalAlignment="Left"
Height="603"
Margin="0,51,0,0"
x:Name="usersPan"
VerticalAlignment="Top"
Width="1286"
Loaded="FrameworkElement_OnLoaded">
and then from code-behind you can access grid in next way:
private void FrameworkElement_OnLoaded(object sender, RoutedEventArgs e)
{
var grid = sender as Grid;
if (grid != null)
{
grid.Width = 0;
}
}
Better solution :
Add some boolean property to your ViewModel like public bool IsGridVisible{get;set;}
And bind it to your Grid
<Grid HorizontalAlignment="Left"
Height="603"
Margin="0,51,0,0"
x:Name="usersPan"
VerticalAlignment="Top"
Width="1286"
Visibility="{Binding Path=IsGridVisible, Converter={StaticResource BoolToVis}">
where BoolToVis is converter which converts true to Visible and false to Hidden. You can define it in App.xaml like :
<BooleanToVisibilityConverter x:Key="BoolToVis" />
I was able to do something like this so I can change properties outside of an event.
private Grid userGrid;
private void onUserGridLoaded(object sender, RoutedEventArgs e)
{
userGrid = sender as Grid;
}
I have a function I would like to run on after update of a lot of different text boxes, is it possible to listen for a generic after update event rather than the specific events?
So rather than 100 individual calls to the function, just one listener?
Edit: It would appear we are using a combination of MVVM and traditional code behind.
Here is one of the textboxes:
<TextBox Text="{Binding APhaseFrom}" x:Name="txtFromWhereA" TabIndex="26" HorizontalContentAlignment="Center" HorizontalAlignment="Left" Height="48" TextWrapping="NoWrap" VerticalAlignment="Top" Width="261" FontSize="26" FontWeight="Bold" BorderBrush="Black" BorderThickness="1" Margin="289,656,0,0" GotMouseCapture="txtFromWhereA_GotMouseCapture" GotFocus="txtFromWhereA_GotFocus" Grid.Row="3" />
The code from the view Model:
public string APhaseFrom
{
get { return new string((char[])_f.Rows[1].GetValue("Alpha09")); }
set
{
if (value.Length <= 35)
{
_f.Rows[1].SetValue("Alpha09", value);
}
else
{
MessageBox.Show("Error: String length Longer than 35 Characters.");
}
}
}
We also are using some commands for other processes:
public ICommand Updatesql
{
get;
internal set;
}
private void CreateUpdatesql()
{
Updatesql = new RelayCommand(UpdatesqlExecute);
}
private void UpdatesqlExecute()
{
_f.Update();
}
Should I be using commands or just link the events to functions in the viewmodel?
Since you are using WPF, and if I understand your problem correctly, then the RoutedEvents that WPF uses may help you here. Essentially, events like the LostFocus event of a TextBox will bubble up your UI hierarchy and can be handled by a common parent control. Consider this snippet of XAML and codebehind:
<StackPanel TextBox.LostFocus="TextBoxLostFocus">
<TextBox></TextBox>
<TextBox></TextBox>
<TextBox></TextBox>
</StackPanel>
Codebehind:
private void TextBoxLostFocus(object sender, RoutedEventArgs e)
{
MessageBox.Show("Lost Focus!");
}
You will find that the event handler is called for any of the three textboxes when focus is lost. The sender parameter or e.Source can be used to find the textbox that fired the event.
This pattern holds true for any RoutedEvent, so things like Button.Click or TextBox.TextChanged and many more can be caught in this manner.
Really and truthfully you should be using a single design pattern... ie MVVM when writing WPF applications, each textbox would be bound to a property which implements the INotifyPropertyChange interface.
In the setter of each property you would essentially update the value, fire a property changed event and then either make a call to your method or simply add an event handler on the view model for the PropertyChanged event.
Also... MessageBox.Show is a bad idea in your view models, its hard to unit test it.
Update
I removed my previous ideas because I now understand more clearly what you are looking for.
But you definitely need to use the LostFocus event.
<TextBox Text="{Binding APhaseFrom}" x:Name="txtFromWhereA" LostFocus="OnLostFocus" />
I want make validation in my WPF application. And the approach I want to use is I want to take custom action if any value of my controls has been changed.
How I can do that suppose I have control like this
<TextBox x:Name="TextBox1" Text="{Binding Path=Box1,UpdateSourceTrigger=PropertyChanged}" />
<TextBox x:Name="TextBox2" Text="{Binding Path=Box2,UpdateSourceTrigger=PropertyChanged}" />
And If user change the value one of that control I want to create custom action for example (For my thinking )
private void Window_Controls_Property_Changed(object sender,RoutedEventArgs e){
if(((Control)sender)=="TextBox1")
MessageBox.Show("Show message here of validation some control","Attention",MessageBoxButton.OK);
}
I'm still confusing combine the INotifyPropertyChanged or ValidationRule with displaying error what I want with MessageBox. I'm still newbie using this kind of features.
I have read many articles about INotifyPropertyChanged or ValidationRule but I'm still don't know how to get the custom action like I said before. And the custom validation may use another textbpx value to validate with the other textbox.
Any helps?..
You can register the handler on the Container that hosts your TextBox's. Like this:
<StackPanel TextBox.LostFocus="TextBox_OnLostFocus">
<TextBox x:Name="TextBox1" Text="{Binding Path=Box1,UpdateSourceTrigger=PropertyChanged}" />
<TextBox x:Name="TextBox2" Text="{Binding Path=Box2,UpdateSourceTrigger=PropertyChanged}" />
</StackPanel>
This way the same handler will be used for all TextBox's and you can query e.Source to find out which TextBox triggered the event.
for Validation in mvvm you can take IDataErrorInfo. there are examples all over the net.
and if you really whant to do some special action when a property in your viewmodel change, you can simply subscribe to your own viewmodel PropertyChanged event and handle your stuff
You may want to read this block post about BindingGroups and validation (and this related blog post). They show you how you can validate multiple controls at once using custom validation rules.
<TextBox HorizontalAlignment="Left" LostFocus="OnLostFocus"/>
Here's an easy way. Validate using the LostFocus Event in WPF
private void TextBox_LostFocus_1(object sender, RoutedEventArgs e) {
var thisTextBox = (TextBox)sender;
if (thisTextBox.Text == "") {
MessageBox.Show("Validate!");
}
}
I am writing a windows-phone 7 application. I've got a page with a list of TextBlock(s) contained in a ListBox. The behavior I want is that upon clicking one of those TextBlock(s) the page is redirected to a different one, passing the Text of that TextBlock as an argument.
This is the xaml code: (here I am binding to a collection of strings, and the event MouseLeftButtonDown is attached to each TextBlock).
<ListBox x:Name="List1" ItemsSource="{Binding}">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock MouseLeftButtonDown="List1_MouseLeftButtonDown" Text="{Binding}"
FontSize="20"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
But this has been unsuccessful for me. I have tried attaching MouseLeftButtonDown event to either the individual TextBox(es) or to the ListBox. And I have had exceptions raised as soon as I use NavigationService.Navigate(uri). Which event should be attached? Should the event be attached to the individual items or to the list as a whole?
I have found a way to work around this problem by populating ListBox with HyperlinkButton(s). However, I would like to understand why the TextBox approach did not work.
This is my first attempt with Silverlight, so I might be missing something basic here.
There are a few ways to do this but I'll walk you through one of the the simplest (but not the purest from an architectural perspective).
Basically you want to find out when the selection of the ListBox changes. The ListBox raises a SelectionChanged event which can be listened to in the code behind.
<ListBox x:Name="List1" ItemsSource="{Binding}" SelectionChanged="SelectionChangedHandler" SelectionMode="Single" >
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding}" FontSize="20"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Then have a handler something like:
private void SelectionChangedHandler(object sender, SelectionChangedEventArgs e)
{
IList selectedItems = e.AddedItems;
string val = selectedItems.OfType<string>().FirstOrDefault();
NavigationService.Navigate(new Uri(val));
}
One thing you'll need to be aware of is that ListBoxes support multiple selection. For this reason, the event arguments give you back a list of the selected items. For simplicity, all I've done is taken the first value from this list and used that as the navigation value. Notice how I've also set the SlectionMode property of the ListBox to Single which will ensure the user can only select one item.
If I were doing this for real I'd look into creating an TriggerAction tat can be hooked up to an event trigger through xaml which will remove the for code behinds. Take a look at this link if you're interesetd.
In addition to Chris' and James' replies, I'd add that you will also need to clear the listbox selection in the event handler, otherwise the user won't be able to tap the same item twice on the listbox (because the item will already be selected).
Using James' approach, I would change the SelectionChangedHandler() implementation as follows:
private void SelectionChangedHandler(object sender, SelectionChangedEventArgs e)
{
// Avoid entering an infinite loop
if (e.AddedItems.Count == 0)
{
return;
}
IList selectedItems = e.AddedItems;
string val = selectedItems.OfType<string>().FirstOrDefault();
NavigationService.Navigate(new Uri(val));
// Clear the listbox selection
((ListBox)sender).SelectedItem = null;
}
What I would recommend is binding the SelectedItem property of the ListBox to a property in your ViewModel. Then, on the ListBox's SelectedItemChanged event, navigate to to the appropriate URL passing the data key on the QueryString, or upgrade to something like MVVM Light and put the actual SelectedItem object on the message bus for the child window to pick up. I have a sample of this second method on my Skydrive that you can check out.
HTH!
Chris