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Unable to Update XAML TextBlock Text Binding

I have a TextBlock in XAML that's bound to a property called EditsWarning:
<TextBlock DockPanel.Dock="Top" Text="{Binding EditsWarning, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Style="{DynamicResource Esri_TextBlockRegular}" HorizontalAlignment="Left" FontSize="14" FontWeight="DemiBold" VerticalAlignment="Center" Margin="10,0,10,5" TextWrapping="WrapWithOverflow"/>
The Definition for the EditsWarning Property is here:
public string EditsWarning
{
get { return editsWarningMessage; }
set
{
SetProperty(ref editsWarningMessage, value, () => this.EditsWarning);
}
}
The EditsWarning Property is set to an instance of a class like this:
editsWarning = new OutstandingEditsTextBlock();
editsWarningMessage = editsWarning.EditsWarningMessage.ToString();
And the OutstandingEditsTextBlock class is here, and implements INotifyPropertyChanged
internal class OutstandingEditsTextBlock : INotifyPropertyChanged
{
private string editsWarning;
public OutstandingEditsTextBlock()
{
if (Project.Current.HasEdits)
{
this.editsWarning = "This session/version has outstanding edits.";
}
else
{
this.editsWarning = string.Empty;
}
}
public event PropertyChangedEventHandler PropertyChanged;
public string EditsWarningMessage
{
get { return this.editsWarning; }
set
{
this.editsWarning = value;
this.OnPropertyChanged("EditsWarningMessage");
}
}
public void OnPropertyChanged(string propertyName)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
I noticed that I can get it to display either value, however, I can never get it to update in the same debugging session. In fact, it looks like the setter for the public property is never hit.
Can someone please help me figure out what I'm doing wrong?
Thank you.

Bound target not updating when button pressed to change value

I have some code which uses a form. The form is bound to my class, FormData. I have binding working well and updating my formData (local instance), but when I try to change the value of one of the variables in formData on button click/LostFocus trigger, it doesn't update.
Here's my relevant XAML:
<TextBox x:Name="friendly_name_textBox"
Style="{StaticResource TextErrorStyle}"
Text="{Binding
PrimaryUserName,
Mode=TwoWay,
ValidatesOnExceptions=True,
ValidatesOnDataErrors=True,
UpdateSourceTrigger=PropertyChanged,
NotifyOnValidationError=True}"
HorizontalAlignment="Left"
Margin="0,75,0,0"
TextWrapping="Wrap"
VerticalAlignment="Top"
Width="120"/>`
The button trigger (which does get run):
private void Button_Click(object sender, RoutedEventArgs e)
{
formData.PrimaryUserName = "TEST";
}
And my FormData code:
public string PrimaryUserName
{
get
{
return primaryUserNameValue;
}
set
{
if(primaryUserNameValue != value)
{
primaryUserNameValue = value;
}
}
}

You need to implement the INotifyPropertyChanged interface and raise the PropertyChanged event in your formData class:
public class formData : INotifyPropertyChanged
{
private string primaryUserNameValue;
public string PrimaryUserName
{
get
{
return primaryUserNameValue;
}
set
{
if (primaryUserNameValue != value)
{
primaryUserNameValue = value;
NotifyPropertyChanged();
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}

Your Class needs to implement INotifyPropertyChanged, so that the target knows if the source property changes:
https://learn.microsoft.com/en-us/dotnet/framework/wpf/data/how-to-implement-property-change-notification
It's really easy, please have a look at the documentation and adjust your code accordingly. Your Property would have to look like this:
public string PrimaryUserName
{
get
{
return primaryUserNameValue;
}
set
{
if(primaryUserNameValue != value)
{
primaryUserNameValue = value;
OnPropertyChanged("PrimaryUserName");
}
}
}
But you also need the event and onPropertyChanged function to make it work.
Happy Coding!

Check Box binding WPF

I have 3 checkboxes. Lets call them cb1,cb2 and cb3. The cb3 should be checkëd when cb1 and cb2 are checked. How do I Implement this in WPF.? I am new to WPF.
Thanks in advance.

If you are using a ViewModel, just add a new computed property to that.
A simple view model would look like:
public class MyVieWModel : INotifyPropertyChanged
{
private bool _cb1Checked;
private bool _cb2Checked;
public bool CB1Checked
{
get { return _cb1Checked; }
set
{
_cb1Checked = value;
PropertyChanged(this, new PropertyChangedEventArgs("CB1Checked"));
PropertyChanged(this, new PropertyChangedEventArgs("CB3Checked"));
}
}
public bool CB2Checked
{
get { return _cb2Checked; }
set
{
_cb2Checked = value;
PropertyChanged(this, new PropertyChangedEventArgs("CB2Checked"));
PropertyChanged(this, new PropertyChangedEventArgs("CB3Checked"));
}
}
public bool CB3Checked
{
get { return _cb1Checked && _cb2Checked; }
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
After setting CB1Checked or CB2Checked, you need to raise the event that CB3Checked has also changed.
Your XAML would look something like (and this is from memory...):
<CheckBox IsChecked={Binding CB1Checked}" />
<CheckBox IsChecked={Binding CB2Checked}" />
<CheckBox IsChecked={Binding CB3Checked, Mode=OneWay}" />
As #wkl points out in the comments, the third checkbox should be a one-way binding since the value can't be set.
Some MVVM frameworks might make this a little easier for you, I've not used any to be able to recommend though.

You can do it like this for a single checkbox:
<CheckBox x:Name="cb3" IsChecked="{Binding Path=IsChecked, ElementName=cb2}" />
I assume the other checkbox is called cb2.
For multiple checkboxes I recommend a Binding in you DataContext.
<CheckBox IsChecked="{Binding Path=CB_1_Checked}" Content="CheckBox 1" />
public bool CB_1_Checked
{
get { return _cb_1_checked; }
set
{
_cb_1_checked = value;
OnPropertyChanged();
//Notify that CB_3_Checked may have changed:
OnPropertyChanged("CB_3_Checked");
}
}
Do this for CB1 and CB2.
Add this for CB3
//Will return 'true' when both are checked (but lacks OnPropertyChanged !)
public bool CB_3_Checked => (CB_1_Checked && CB_2_Checked);
Or with a little more options:
private bool _cb_3_checked;
public bool CB_3_Checked
{
get
{
if(CB_1_Checked && CB_2_Checked)
{
_cb_3_checked = true;
}
return _cb_3_checked;
}
set
{
_cb_3_checked = value;
OnPropertyChanged();
}
}
Read more about Bindings here.

Getting IsChecked Property of a CheckBox in a ListBox

So many examples found and none fit! My list box is a list of Result objects. Results can be checked or unchecked in a listbox to mark them as 'Allowed to 'transmit.
<ListBox
x:Name="FileListBox"
ItemsSource="{Binding TestResults}"
ItemTemplate="{StaticResource FileListTemplate}"
SelectionMode="Single"
SelectedItem="{Binding FileListSelected}"
Background="#FFFFFBE2" />
The FileListTemplate
<DataTemplate x:Key="FileListTemplate">
<Grid HorizontalAlignment="Stretch">
<Grid.RowDefinitions>
<RowDefinition />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width=".5*" />
<ColumnDefinition Width=".3*" />
<ColumnDefinition Width=".2*" />
</Grid.ColumnDefinitions>
<TextBlock Grid.Column="0"
Text="{Binding FileName}" />
<TextBlock Grid.Column="1"
Text="Machine">
</TextBlock>
<CheckBox x:Name="UploadOK"
Grid.Column="2"
HorizontalAlignment="Right"
IsChecked="{Binding CanUpload, Mode=TwoWay}" />
</Grid>
</DataTemplate>
I took out a lot of formatting code to reduce the clutter. So when the check box is checked (or un checked) I need to set a boolean on the object to true or false. But I do not want the ListItem selected just because the checkbox is selected. When the ListItem is selected something else happens. Here is the code for that.
public TestResult FileListSelected
{
get
{
return selectedItem;
}
set
{
if (value == selectedItem)
return;
selectedItem = value;
if (!Workspaces.Any(p => p.DisplayName == value.FileName))
{
this.DisplayTestResult(value as TestResult);
}
base.RaisePropertyChanged("FileListSelected");
}
}
And here is the code I bound to for the Checkbox (although it didn't work).
public bool CanUpload
{
get { return selectedItem.CanUpload; }
set
{
selectedItem.CanUpload = value;
}
}
I appreciate you looking at this.

Internal Class TestResult
{
...
private bool _canUpload;
public bool CanUpload
{
get { return _canUpload; }
set
{
_canUpload = value;
base.RaisePropertyChanged("CanUpload");
}
}
}

When working with MVVM always check for the following:
Add using System.ComponentModel; to your ViewModelClass
Inherit from INotifyPropertyChanged
Always check your DataContext and see the Output Window for BindingErrors
Create Bindings like this:
Example Property:
public string Example
{
get { return _example; }
set
{
_example= value;
OnPropertyChanged();
}
}
this will call OnPropertyChanged automatically every time a new value is assigned (not updated automaticaly once it changes from some other location!)
Make sure your Implementation of INotifyPropertyChanged looks like this:
private void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
for that you also need using System.Runtime.CompilerServices;
Other options to get your code working:
Your TestResults sould be an ObservableCollection<TestResult>
TestResult should have a property for CanUpload and FileName and inherit from INotifyPropertyChanged
Then on your MainViewModel for example on and ButtonClick your can get the selected files like this:
private List<string> GetSelectedFiles()
{
return TestResults.Where(result => result.CanUpload == true).Select(r => r.FileName).ToList());
}
Note:
FileListSelected is a Property of your ListBox's DataContext which is different to the DataContext of an entry (or at least should be).
FileListSelected will then return the selected Item of your ItemsSource.
Maybe you can comment on this problem with the row selection/checkbox check and add some detail so I can help you more.
EDIT: Notify MainWindowViewModel about CheckBox State Changes:
I see two possible approaches here:
USING EVENT
Add this to your TestResult class:
public delegate void CheckBoxStateChangedHandler(object sender, CheckBoxStateChangedEventArgs e);
public event CheckBoxStateChangedHandler CheckBoxStateChanged;
public class CheckBoxStateChangedEventArgs
{
bool CheckBoxChecked { get; set; }
}
Make sure that on creation of a new TestResult in your MainViewModel you subscribe to that event;
testResult.CheckBoxStateChanged += CheckBox_StateChanged;
Handle what you want to do once the state is changed in CheckBox_StateChanged. Note that the argument e contains the boolean (Checked) and the corresponding TestResult as the sender.
You simply invoke your new Event in the Setter of your CheckBox.Checked Binding:
public bool Checked
{
get { return _checked; }
set
{
_checked = value;
OnPropertyChanged();
CheckBoxStateChanged.Invoke(this, new CheckBoxStateChangedEventArgs() { CheckBoxChecked = value })
}
}
CALL METHOD ON MAINWINDOWVIEWMODEL
for that you need o create a static object of your MainWindowViewModel (in your MainViewModel) - don't forget to assigne a value once you create your MainWindowViewModel.
public static MainViewModel Instance { get; set; }
then simply add a public Method as you need:
public void CheckBoxValueChanged(bool value, TestResult result)
{
//Do whatever
}
you can also call in from the same spot as the event from above is invoked.
public bool Checked
{
get { return _checked; }
set
{
_checked = value;
OnPropertyChanged();
MainWindowViewModel.Instance.CheckBoxValueChanged(value, this);
}
}

How can I avoid recursion when updating my ViewModel properties?

In my View I have a slider and a combobox.
When I change the slider, I want the combobox to change.
When I change the combobox, I want the slider to change.
I can udpate one or the other, but if I try to update both I get a StackOverflow error since one property keeps updating the other in an infinite loop.
I've tried putting in a Recalculate() where the updating is done in one place, but still run into the recursion problem.
How can I have each control update the other without going into recursion?
in View:
<ComboBox
ItemsSource="{Binding Customers}"
ItemTemplate="{StaticResource CustomerComboBoxTemplate}"
Margin="20"
HorizontalAlignment="Left"
SelectedItem="{Binding SelectedCustomer, Mode=TwoWay}"/>
<Slider Minimum="0"
Maximum="{Binding HighestCustomerIndex, Mode=TwoWay}"
Value="{Binding SelectedCustomerIndex, Mode=TwoWay}"/>
in ViewModel:
#region ViewModelProperty: SelectedCustomer
private Customer _selectedCustomer;
public Customer SelectedCustomer
{
get
{
return _selectedCustomer;
}
set
{
_selectedCustomer = value;
OnPropertyChanged("SelectedCustomer");
SelectedCustomerIndex = _customers.IndexOf(_selectedCustomer);
}
}
#endregion
#region ViewModelProperty: SelectedCustomerIndex
private int _selectedCustomerIndex;
public int SelectedCustomerIndex
{
get
{
return _selectedCustomerIndex;
}
set
{
_selectedCustomerIndex = value;
OnPropertyChanged("SelectedCustomerIndex");
SelectedCustomer = _customers[_selectedCustomerIndex];
}
}
#endregion

try in the set functions something like:
public int SelectedCustomerIndex
{
get
{
return _selectedCustomerIndex;
}
set
{
if (value != _selectedCustomerIndex)
{
_selectedCustomerIndex = value;
OnPropertyChanged("SelectedCustomerIndex");
SelectedCustomer = _customers[_selectedCustomerIndex];
}
}
}
to fire the events only when there is an actual change in value. This way, a second call to the set property with the same value does not cause another change event.
You have to do that for the other property as well of course.

Both properties are called from each other, hence the recursion. Not related to binding at all. Proper way is to change each other and fire change notification for both properties when either property changes:
public Customer SelectedCustomer
{
get
{
return _selectedCustomerIndex;
}
set
{
_selectedCustomer = value;
_selectedCustomerIndex = _customers.IndexOf(value);
OnPropertyChanged("SelectedCustomer");
OnPropertyChanged("SelectedCustomerIndex");
}
}
public int SelectedCustomerIndex
{
get
{
return _selectedCustomerIndex;
}
set
{
_selectedCustomerIndex = value;
_selectedCustomer = _customers[_selectedCustomerIndex];
OnPropertyChanged("SelectedCustomer");
OnPropertyChanged("SelectedCustomerIndex");
}
}