C# WPF add character to textbox without binding

Question

Can i simply add characters without binding this characters to my ViewModel? I need these to show physical units like cm, mm, m, cm^3, ...

XAML:

<TextBox 
Text="{Binding value_top}" //sth. like + "cm"
HorizontalAlignment="Left" 
VerticalAlignment="Top" 
Width="50"/>

VW:

value_top = 22.9

Output aim:

22.9 cm

I know, I can overlay a Label, but i would like to know if there is another possibility.

Answer 1

Create a converter which will take the double and return a string. Here is an untested example to get you started:

public class DoubleToString: IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var dbl = (double) value;

        return $"{dbl} cm";           
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return Double.Parse(Regex.Match(value.ToString(), "[\d.]+").Value);    
    }
}