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Command does not execute on form initialize for radio button

My form has 2 radio buttons. When you press either one of them it executes a command that sets a string variable with the relative value for radio button set to true - this also has a CommandParameter that sends the value of the string Content into the Exectue function.
This works fine when a human is pressing a radio button. Variables get set and all is good.
However, I have coded in the xaml for one of the radio buttons to be set to checked by default - and this does not cause the command to be executed on startup of the form for the very first time. Hence the string variable that I hold the appropriate value for the radio button that is checked, never gets set.
How do I get my string variable recieve the value on startup from the Execute(param) method?
Here is the xaml:
<StackPanel Grid.Row="4" Grid.Column="1" Margin="3" Orientation="Horizontal">
<RadioButton GroupName="LcType" Name="TsMapPane" HorizontalAlignment="Left" Checked="TsMapPane_Checked" IsChecked="True"
Command="{Binding Path=LcTypeCommand}" CommandParameter="{Binding ElementName=TsMapPaneTextBox, Path=Text}" >
<RadioButton.Content>
<TextBlock Name="TsMapPaneTextBox" Text="TS_MAP_PANE"/>
</RadioButton.Content>
</RadioButton>
<RadioButton GroupName="LcType" Margin="10 0 0 0" Name="TsGroup" HorizontalAlignment="Left" Checked="TsGroup_Checked"
Command="{Binding Path=LcTypeCommand}" CommandParameter="{Binding ElementName=TsGroupTextBox, Path=Text}">
<RadioButton.Content>
<TextBlock Name="TsGroupTextBox" Text="TS_GROUP"/>
</RadioButton.Content>
</RadioButton>
</StackPanel>
Here is the ViewModel:
public ICommand LcTypeCommand { get; set; }
public MyViewModel()
{
LcTypeCommand = new RelayCommand((param) => LcTypeExecute(param), () => true);
}
private void LcTypeExecute(object param)
{
LcTypeName = param.ToString();
}
public string LcTypeName
{
get => _lcTypeName;
set => SetField(ref _lcTypeName, value);
}

The command is called only when the user clicks on the button.
Changing the state of the RadioButton raises the Checked and Unchecked events. You can connect a command to the Checked event, but there is no guarantee that the IsChecked property will be changed after the listener is connected. Since both are specified in XAML.
In my opinion, the most correct would be to call the command in Code Behind after XAML initialization.
InitializeComponent();
if (TsMapPane.Command is ICommand command &&
command.CanExecute(TsMapPane.CommandParameter))
{
command.Execute(TsMapPane.CommandParameter);
}
P.S. You can add the following extension method to the Solution:
public static partial class WinHelper
{
public static void TryExecute(this ICommandSource commandSource)
{
if (commandSource.Command is not ICommand command)
return;
if (command is RoutedCommand routedCommand)
{
IInputElement? target = commandSource.CommandTarget ?? commandSource as IInputElement;
if (routedCommand.CanExecute(commandSource.CommandParameter, target))
{
routedCommand.Execute(commandSource.CommandParameter, target);
}
}
else
{
if (command.CanExecute(commandSource.CommandParameter))
{
command.Execute(commandSource.CommandParameter);
}
}
}
}
Then the code will be simplified to this:
InitializeComponent();
TsMapPane.TryExecute();
shows a null value for "TsMapPane.CommandParameter"
At the time of XAML initialization, if the DataContext is assigned by an external container, bindings to the DataContext will not yet work.
Therefore, you need to execute the command once in the Loaded event:
public SomeWindow()
{
InitializeComponent();
Loaded += OnLoaded;
}
private void OnLoaded(object sender, RoutedEventArgs e)
{
Loaded -= OnLoaded;
TsMapPane.TryExecute();
}

WPF .NET unable to add new instance to ObservableCollection

I am new to WPF and losing my mind with issues. I have a view, viewmodel and model. I want the user user to fill in some information in the view, press button to confirm and then have a new instance of the model (with the user specified parameters) added to the ObservableCollection and to my local database.
View: (unrelated stuff hidden)
<TextBox DataContext="{DynamicResource RiderequestViewModel}" Margin="15,0,15,0" Grid.Column="1" Grid.Row="1" FontSize="12" Height="25" Text="{Binding Riderequest.Time}"/>
<TextBox DataContext="{DynamicResource RiderequestViewModel}" Margin="15,0,15,0" Grid.Column="1" Grid.Row="2" FontSize="12" Height="25" Text="{Binding Riderequest.LocationFrom}"/>
<TextBox DataContext="{DynamicResource RiderequestViewModel}" Margin="15,0,15,0" Grid.Column="1" Grid.Row="3" FontSize="12" Height="25" Text="{Binding Riderequest.LocationTo}"/>
<Button DataContext="{DynamicResource RiderequestViewModel}" x:Name="nextBtn" Grid.Column="0" Grid.ColumnSpan="2" Grid.Row="5" Content="Verder" Width="150" Foreground="White" Command="{Binding AddRiderequestCommand}" Click="NextBtn_Click"/>
ViewModel RiderequestViewModel:
namespace Drink_n_Drive.ViewModel
{
class RiderequestViewModel: BaseViewModel
{
private Riderequest riderequest;
private ObservableCollection<Riderequest> riderequests;
public ObservableCollection<Riderequest> Riderequests
{
get
{
return riderequests;
}
set
{
riderequests= value;
NotifyPropertyChanged();
}
}
public Riderequest Riderequest
{
get
{
return riderequest;
}
set
{
riderequest= value;
NotifyPropertyChanged();
}
}
public ICommand AddRiderequestCommand { get; set; }
public ICommand ChangeRiderequestCommand { get; set; }
public ICommand DeleteRiderequestCommand { get; set; }
public RiderequestViewModel()
{
LoadRiderequests(); //load existing from DB
LinkCommands(); //Link ICommands with BaseCommands
}
private void LoadRiderequests()
{
RiderequestDataService riderequestDS = new RiderequestDataService();
Riderequests= new ObservableCollection<Riderequests>(riderequestDS .GetRiderequests());
}
private void LinkCommands()
{
AddRiderequestCommand = new BaseCommand(Add);
ChangeRiderequestCommand = new BaseCommand(Update);
DeleteRiderequestCommand = new BaseCommand(Delete);
}
private void Add()
{
RiderequestDataService riderequestDS = new RitaanvraagDataService();
riderequestDS.InsertRiderequest(riderequest); //add single (new) instance to the DB
LoadRiderequests(); //Reload ObservableCollection from DB
}
private void Update()
{
if (SelectedItem != null)
{
RiderequestDataService riderequestDS = new RiderequestDataService();
riderequestDS.UpdateRiderequest(SelectedItem);
LoadRiderequests(); //refresh
}
}
private void Delete()
{
if (SelectedItem != null)
{
RiderequestDataService riderequestDS = new RiderequestDataService();
riderequestDS.DeleteRiderequest(SelectedItem);
LoadRiderequests();
}
}
private Riderequest selectedItem;
public Riderequest SelectedItem
{
get { return selectedItem; }
set
{
selectedItem = value;
NotifyPropertyChanged();
}
}
}
}
Pressing the button simply does nothing and I don't know why. I also have a diffrent page where I want to show a datagrid of all instances in the ObservableCollection like this:
<DataGrid Grid.Row="1" Grid.ColumnSpan="2" Grid.RowSpan="3" DataContext="{DynamicResource RitaanvragenViewModel}" ItemsSource="{Binding Ritaanvragen}" SelectedItem="{Binding SelectedItem}" />
But the grid just shows completly empty. I have added some dummydata to my DB but still doesn't work.
My appologies for the mix of English and Dutch in the code.

I'm not 100% sure about it but i would do something like this:
As for first step I would change the TextBox to look like this:
<TextBox DataContext="{DynamicResource Ritaanvraag}" Margin="15,0,15,0" Grid.Column="1" Grid.Row="1" FontSize="12" Height="25" Text="{Binding Path=Time, Mode=OneWayToSource}"/>
There's no need to pass your ViewModel to it as a DataSource because your View's first few meta-data related lines should already define what ViewModel does it belong to.
When you not specify the type of your binding, it will use a default binding type which depends on the current object. You're using a TextBox now so it will have a TwoWay binding by default.
If you only want to accept data from the user and you don't want to show the data if your model has any then you should use OneWayToSource. (Note: OneWay is a direction between source -> view.)
I would also remove the DataSource from your DataGrid because you already set it's ItemSource:
<DataGrid Grid.Row="1" Grid.ColumnSpan="2" Grid.RowSpan="3" ItemsSource="{Binding Ritaanvragen}" SelectedItem="{Binding SelectedItem}" />

Validate a TextBox upon button press in WPF/MVVM

I have a TextBox and a Button in my view. I have an ICommand method, String serial number property, and a IsEnabled property in my view model.
When the user clicks the Button I'd like to validate the serial number in the TextBox with the InDatabase property. If the contents in the TextBox are invalid, I would like to raise an error on the TextBox. If the contents are valid in the TextBox I'd like to disable the Button and execute the command.
Here is the view:
<StackPanel Width="Auto" Height="Auto" VerticalAlignment="Center" HorizontalAlignment="Center">
<UniformGrid Rows="3" >
<TextBlock Text="This device appears to be uninitialized."/>
<UniformGrid Rows="1" Columns="2">
<Label>Serial Number:</Label>
<TextBox Text="{Binding IdentifiedSerialNumber, Mode=TwoWay, ValidatesOnDataErrors=True}"></TextBox>
</UniformGrid>
<Button Content="Identify" Command="{Binding IdentifyCommand}" IsEnabled="{Binding CanExecuteDeviceRestoration}"/>
</UniformGrid>
</StackPanel>
Here is the view-model:
public string IdentifiedSerialNumber
{
get
{
return this.identifiedSerialNumber;
}
set
{
this.identifiedSerialNumber = value;
}
}
public ICommand IdentifyCommand
{
get
{
return new RelayCommand(this.RelayRestoreControllerIdentity);
}
}
public bool CanExecuteDeviceRestoration
{
get
{
return canExecuteDeviceRestoration;
}
private set
{
this.canExecuteDeviceRestoration = value;
RaisePropertyChanged("CanExecuteDeviceRestoration");
}
}
public async void RelayRestoreControllerIdentity()
{
await Task.Run(
() =>
{
this.RestoreControllerIdentity();
});
}
public bool InDatebase
{
get
{
return DatabaseConnection.DeviceExists(this.IdentifiedSerialNumber);
}
}
My question is how do I bind the behavior such that when the user click the Button the TextBox is validated, and if it fails it displays an error with a message and if it passes the Button will be disabled and the command will execute.

You need to implement IDataErrorInfo.
This would add an indexer which returns a string.
If empty string is returned it means no error.
You can return an empty string until button is pressed(u could use a flag).
when button is pressed,Run the validation logic and appropriately change the flag and Raise PropertyChanged event for IdentifiedSerialNumber
You can learn how to implement IDataErrorInfo from here.
Also you need to Raise PropertyChanged event for IdentifiedSerialNumber.

Force or otherwise initiate TwoWay TestBox data binding

I've got a WPF TextBox with TwoWay binding to a ViewModel property. I also have a ToolBar with a Button. When the Button is clicked, it executes a command on the same ViewModel that will do something with the property the TextBox is bound to.
Unfortunately it looks like the Binding only sends the text back to the binding target when the TextBox loses focus. The Button on the Toolbar however does not take focus when clicked. The upshot being that when the Command executes it does not have the text from the textbox, but rather the last value that was bound.
The Xaml looks like so:
<DockPanel LastChildFill="True" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" >
<ToolBarTray Background="White" DockPanel.Dock="Top">
<ToolBar Band="1" BandIndex="1">
<Button Command="{Binding QueryCommand}">
<Image Source="images\media_play_green.png" />
</Button>
</ToolBar>
</ToolBarTray>
<DataGrid VerticalAlignment="Top" DockPanel.Dock="Top" Height="450" AutoGenerateColumns="True"
ItemsSource="{Binding}" DataContext="{Binding Results}" DataContextChanged="DataGrid_DataContextChanged"/>
<TextBox DockPanel.Dock="Bottom" Text="{Binding Sql, Mode=TwoWay}"
AcceptsReturn="True" AcceptsTab="True" AutoWordSelection="True" TextWrapping="WrapWithOverflow"/>
</DockPanel>
How do I get the TextBox's Text binding to update the ViewModel when the ToolBar button is pressed. There is nothing fancy going on in the ViewModel which looks like so:
public class MainViewModel : ViewModelBase
{
private readonly IMusicDatabase _database;
/// <summary>
/// Initializes a new instance of the MainViewModel class.
/// </summary>
public MainViewModel(IMusicDatabase database)
{
_database = database;
QueryCommand = new RelayCommand(Query);
}
public RelayCommand QueryCommand { get; private set; }
private async Task QueryAndSetResults()
{
Results = await _database.Query(Sql);
}
private void Query()
{
QueryAndSetResults();
}
private IEnumerable<object> _results;
public IEnumerable<object> Results
{
get
{
return _results;
}
private set
{
Set<IEnumerable<object>>("Results", ref _results, value);
}
}
private string _sql = "SELECT * FROM this WHERE JoinedComposers = 'Traditional'";
public string Sql
{
get { return _sql; }
set
{
Set<string>("Sql", ref _sql, value);
}
}
}

You can use the UpdateSourceTrigger property of the binding, setting it to PropertyChanged makes the TextBox refresh the binding every time the text changes, not just when losing focus:
<TextBox DockPanel.Dock="Bottom"
Text="{Binding Sql, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
AcceptsReturn="True"
AcceptsTab="True"
AutoWordSelection="True"
TextWrapping="WrapWithOverflow"/>
More info at MSDN.

OnPropertyChanged method is not firing

In WP8 app, i have few controls where i bind the foreground color which i am changing in the codebehind. But OnPropertyChanged is not firing when the user event happened.
I have defined this binding "ControlForeground" in my textblock and radiobutton data template controls in it. I am trying to change the Foreground color whenever user presses the button. But my new color assignment is not updating the UI. Anything i am missing here?
In XAML,
<TextBlock x:Name="lblTileColor" TextWrapping="Wrap" Text="Selected color:" Foreground="{Binding ControlForeground, Mode=TwoWay}"/>
<TextBlock x:Name="lblTileColor2" TextWrapping="Wrap" Text="App bg:" Foreground="{Binding ControlForeground, Mode=TwoWay}"/>
<RadioButton x:Name="accentColor" IsChecked="true" BorderBrush="White" Foreground="{Binding ControlForeground, Mode=TwoWay}">
<RadioButton.ContentTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<Rectangle Width="25" Height="25" Fill="{StaticResource PhoneAccentBrush}"/>
<TextBlock Width="10"/>
<TextBlock x:Name="lblDefaultAccent" Text="Default accent color" Foreground="{Binding ControlForeground, Mode=TwoWay}"/>
</StackPanel>
</DataTemplate>
</RadioButton.ContentTemplate>
</RadioButton>
<Button x:name="UpdateColor" click="update_btn"/>
In C#,
public class ColorClass : INotifyPropertyChanged
{
private SolidColorBrush _ControlForeground;
public SolidColorBrush ControlForeground
{
get
{
return _ControlForeground;
}
set
{
_ControlForeground = value;
OnPropertyChanged("ControlForeground");
}
}
public ColorClass() { }
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string name)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(name));
}
}
public class ColorPage:PhoneApplicationPage{
public ObservableCollection<ColorClass> TestCollection { get; private set; }
public void update_btn(object sender, EventArgs e){
TestCollection.Add(new ColorClass()
{
ControlForeground = new SolidColorBrush(Colors.Red)
});
}
}

For your 2nd problem (not being able to bind controls inside your data template), this is because these controls will use the data context of the their parent template not the data context of the page.
To fix this, you'll have to tell these controls the element name with the data context and give it full path of your property.
<TextBlock
x:Name="lblDefaultAccent"
Text="Default accent color"
Foreground="{Binding DataContext.ControlForeground,
ElementName=LayoutRoot, Mode=TwoWay}"/>
As you can see above you have to specify the element name. In case you bound this using this.DataContext = colorClass then the element name will be the name of the outer grid in your xaml, defaulted as LayoutRoot

You can only bind an ObservableCollection to controls which expect it, like a ListBox or LongListSelector. Additionally, adding a Brush to the TestCollection doesn't fire the non-functional notification since it doesn't call the setter of that property, just modifies the existing object.
Make TestCollection a type ColorClass and change the .Add stuff to just change the ColorClass.ControlForeground property and this should "just work."