When custom string format like "{}{0:N2} pcs." after focus lost the value was not updated if the use changed the content of the TextBox
Create method to internally set and format TextBox text
Remove "pcs." from Text when StringFormat is "pcs. {0:N2}"

now also a StringFormat like "pcs. {0:N2} pcs." works
Handle immediate Value input
#references #938
Correctly reset value if coercing
Added MainWindow changes to show