Properties don't update front-end when written within ICommand-tied function - wpf

Question

UPDATE 3
" I want that the text from this TextBox should be shown in another TextBox(in another view)"
The second textbox in another view is meant to show other information that is tied to the first textbox, but not the copy.
So the user control contains a text box for, say, Bus code. Once I enter bus code, tabbing out will trigger a fetch from the database for other details such as bus name, bus destination, bus model etc.
The others textbox which is in another view then displays the bus name. All following textboxes display destination and so forth. When the command is invoked, and I try to write to the property BusName, it gets assigned (and I call Notify("BusName")) but it does not show on the UI.
Hope that was more clear. Sorry for any confusion caused :).
UPDATE2 - Response to blindmeis
Thanks for your reply though this not appear to be what I was looking for. The tab out is essential because that is how management wants their pages to be populated i.e. when you tab out of a 'code' textbox after entering the code, it will use the code to fetch data from the db to populate the rest of the controls. This does not appear to have the tab-out behavior in it. As for the 3rd dependency property, it is in my original code, I simply did not include it here because the value in the first textbox (user control tabout textbox) is not relevant to the problem. Simply, what I am trying to accomplish is that the second textbox must populate when you tab-out of the first textbox.
I could do this with an eventhandler, but wanted to use commands. I am thinking now perhaps commands are not the way to go here and I should switch to using an event handler.
Please advise if you still have any ideas on how to get the second textbox to populate when you tab out of the first (by putting a breakpoint in populate, you will see that the property gets assigned. ). If I have not understood correctly or missed something here, please let me know. Thanks!
UPDATE!
I have created a VS2013 solution mimicking my code, which reproduces the problem. It is at this public google drive link as a zip file (takes a few seconds for the download icon to appear):
https://drive.google.com/file/d/0B89vOvsI7Ubdbk85SVlvT3U2dVU/view?usp=sharing
You will see that the 2nd text box does not update despite the bound property storing the new value.
Greatly appreciate any help. Thanks in advance.
Original post:
I have a textbox control to which I have tied a key binding based command to go process some actions (in a method that the command has been tied to) when the user hits tab while in the textbox (tabs out).
I have other controls in that page that are boiund to properties in the viewmodel that I write to in that tab-out connected function. When I write my properties in the constructor or somewhere 'outside' that command invokation they seem to work fine and the values show on the page, but when I write them within that command invocation, the properties in the vm contain the values but don't show up on the UI
Any ideas why and how to fix?
Thanks much in advance
From XAML:
<TextBox Name="txtCode" Text="{Binding Path=CodeValue, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
<TextBox.InputBindings>
<KeyBinding Key="Tab" Command="{Binding RetrieveRecordCmd}" > </KeyBinding>
</TextBox.InputBindings>
</TextBox>
From VM:
RetrieveRecordCmd = new GSSCommand(RetrieveRecord, param => this.CanExecuteRetrieveRecordCmd);
Command tied function:
public void RetrieveRecord(object obj)
{
objPie = null;
//Check if a record exists for that code
gssSvcMethodStatusBase = gssSvcClientBase.ReadPies(ref gssSvcGlobalVarsBase, out objPie, out grfaBase, CodeValue);
if ((objPie != null)) // && (objPie.DateCreated > DateTime.MinValue))
PopulatePage(objPie);
else if (objPie == null)
InitiateCreateNew();
else
return;
}

Answer 1

It looks like you have implemented the INotifyPropertyChanged interface in the strict sense, but are missing the actual functionality. The interface itself doesn't automatically give you change notifications. You also need to fire the PropertyChanged event when each property changes. The standard pattern looks like:
private string _name;
public string Name
{
get { return _name; }
set
{
if (_name == value)
return;
_name = value;
NotifyPropertyChanged("Name");
}
}
You should make a habit of writing all mutable properties which you intend to bind to the UI in this format. Snippets can make this easier to do consistently.

Answer 2

this works, but i dont know if this is the behavior you want.
<UserControl x:Class="ProblemDemoWPF.TextBoxTabOutUserControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
Name="TabOutTextUserControl"
>
<StackPanel Margin="0,0,0,0" Orientation="Horizontal">
<Label Content="UserControl (ucTextBox)->"></Label>
<TextBox Width="80" Height="30" BorderBrush="Black"
BorderThickness="2"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Text="{Binding ElementName=TabOutTextUserControl, Path=CodeValue}">
</TextBox>
</StackPanel>
</UserControl>
new Dependency Propertie with right binding without DataContext
public partial class TextBoxTabOutUserControl : UserControl
{
public static readonly DependencyProperty CodeValueProperty =
DependencyProperty.Register("CodeValue", typeof(string), typeof(TextBoxTabOutUserControl));
public string CodeValue
{
get { return (string)GetValue(CodeValueProperty); }
set { SetValue(CodeValueProperty, value); }
}
public TextBoxTabOutUserControl()
{
InitializeComponent();
}
}
Just bind both to LocTextBoxText
<Window x:Class="ProblemDemoWPF.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:loc="clr-namespace:ProblemDemoWPF"
Height="350" Width="525">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="auto"></RowDefinition>
<RowDefinition Height="auto"></RowDefinition>
<RowDefinition Height="auto"></RowDefinition>
<RowDefinition Height="auto"></RowDefinition>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<loc:TextBoxTabOutUserControl Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="2" HorizontalAlignment="left"
CodeValue="{Binding Buscode, Mode=OneWayToSource}"/>
<Label Content="Busname" Grid.Row="1" Grid.Column="0" HorizontalAlignment="Left"></Label>
<TextBox Width="100" Grid.Row="1" Grid.Column="1" Text="{Binding Path=Busname, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"></TextBox>
<Label Content="Busdestination" Grid.Row="2" Grid.Column="0" HorizontalAlignment="Left"></Label>
<TextBox Width="100" Grid.Row="2" Grid.Column="1" Text="{Binding Path=Busdestination, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"></TextBox>
<Label Content="Busmodel" Grid.Row="3" Grid.Column="0" HorizontalAlignment="Left"></Label>
<TextBox Width="100" Grid.Row="3" Grid.Column="1" Text="{Binding Path=Busmodel, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"></TextBox>
</Grid>
</Window>
add Notify to property setter
class MainWindowViewModel : INotifyPropertyChanged
{
private String _buscode;
private string _busname;
private string _busdestination;
private string _busmodel;
public String Buscode
{
get
{
return _buscode;
}
set
{
if (_buscode != value)
{
_buscode = value;
Notify("Buscode");
FetchData(_buscode);
}
}
}
private void FetchData(string buscode)
{
//DB stuff
this.Busname = "Name 1234";
this.Busmodel = "Model 1234";
this.Busdestination = "Destination 1234";
}
public string Busname
{
get { return _busname; }
set { _busname = value; Notify("Busname"); }
}
public string Busdestination
{
get { return _busdestination; }
set { _busdestination = value; Notify("Busdestination"); }
}
public string Busmodel
{
get { return _busmodel; }
set { _busmodel = value; Notify("Busmodel"); }
}
public event PropertyChangedEventHandler PropertyChanged;
protected void Notify(string propertyName)
{
if (this.PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}