How to bind multiple TextBoxes on one label

Question

For my exercise:

I have to concat the values of two input fields (string), in order to show them - through a binding object - in a Label

 

Here the XAML Code:

<div>We published plenty of articles, blogs, videos, in the year 2019 under different categories. Thank you, authors, for all the contributions.</div>
<div> </div>
<div>Here are the top 20 C# Corner authors based on the number of articles, blogs, videos, and total points earned in the year 2019.</div>
<Grid>

<TextBox x:Name="txtFirstName" HorizontalAlignment="Left" Height="45" Margin="35,84,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="144"
Text="{Binding ConcatFullName, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"/>

<TextBox x:Name="txtLastName" HorizontalAlignment="Left" Height="45" Margin="210,84,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="144"
Text="{Binding ConcatFullName, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"/>
<Label x:Name="lblConcat" Content="Name Verkettung" HorizontalAlignment="Left" Margin="403,53,0,0" VerticalAlignment="Top" FontSize="16" FontFamily="Segoe UI Black"/>

<Label x:Name="lblConcatTheFullName" HorizontalAlignment="Left" Margin="403,84,0,0" VerticalAlignment="Top" Width="144"
Foreground="#FF002DFF" FontSize="14" Height="45" Content="{Binding ConcatFullName}"/>
</Grid>

INotifyPropertyChanged with Method FullName

public class FullName : INotifyPropertyChanged
{
private string _ConcatFullName;
public string ConcatFullName
{
get { return _ConcatFullName; }
set
{
if(_ConcatFullName != value)
{
_ConcatFullName = value;
INotifyPropertyChanged("ConcatFullName");
}
}
}

File XAML.cs 

//Here I implement a method to show on the UI the concat of two strings in a label

public MainWindow()
{
InitializeComponent();
this.DataContext = txtFirstName;
this.DataContext = txtLastName;
lblConcatTheFullName.DataContext = FullName();
}
private string FullName()
{
return this.txtFirstName + " " + this.txtLastName;
}

Unfortunately I don't get the desired result. What is wrong with the data Binding?

Is there any other confortable way to solve this problem?

Any help please?

 

Many thanks in advance.

Best regards

Johannes