WPF: Textbox and Binding to Double not able to type . on it

Question

I have a text box like

<TextBox Text="{Binding TransactionDetails.TransactionAmount, Mode=TwoWay, 
UpdateSourceTrigger=PropertyChanged}" Grid.Column="3" Grid.ColumnSpan="2" Grid.Row="5" 
x:Name="TextBoxAmount"/>

And I have taken "TransactionAmount" as Double. Its working well on integer value but when I am typing some Floating point value like 100.456 I am not able to type '.'

Answer 1

You are updating your property every time the value changes. When you type in a ., it is written into your viewmodel and the view is updated.

e.g. if you type in 100. it is rounded to 100, thus you won't see any dot ever.

You have some options to change this behavior:

use a deferred binding:

<TextBox Text="{Binding Path=TransactionDetails.TransactionAmount, 
                        Mode=TwoWay, 
                        UpdateSourceTrigger=PropertyChanged, 
                        Delay=250}" 
         Grid.Column="3" 
         Grid.ColumnSpan="2" 
         Grid.Row="5" 
         x:Name="TextBoxAmount" />

only change the value if it is different from the saved one (I'd recommend this for every binding):

private double _transactionAmount; 
public double TransactionAmount  
{
  get { return _transactionAmount; }    
  set
  { 
    if (_transactionAmount != value)
    {
      _transactionAmount = value; 
      Notify("TransactionAmount"); 
    }
  }

or use some kind of validation, e.g. ValidatesOnExceptions.