try to convert textbox value to int within convert method - wpf

Question

i trying binding textbox value to button IsEnable property but i get an exception.
this is my convert class:
public class BooleanToVisibilityConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
string num = value as string;
int n = int.Parse(num);
if (n > 10) return true;
return false;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
this is my xaml code:
<Button Content="Button" Grid.Column="1" IsEnabled="{Binding ElementName=mytext,Path=Text,Converter={StaticResource convertIntToBool}}" HorizontalAlignment="Left" Margin="83,181,-156,-179" Grid.Row="1" VerticalAlignment="Top" Width="74"/>
<TextBox Grid.Column="1" x:Name="mytext" HorizontalAlignment="Left" Height="23" Margin="263,163,-382,-163" Grid.Row="1" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top" Width="120"/>
i get FormatException: Input string was not in a correct format.

Answer 1

Ok so you want to handle user input in TextBox and make a button enabled or disabled according to this input.
First, you're using int.Parse, meaning that you trust the user to write a number in your TextBox: Don't ever trust user input.
You'll need to use int.TryParse so it doesn't throw an exception if the input isn't a number.
Second, I don't know why you set the TextBox's Text property to "TextBox", that's what is throwing the exception.
Your converter code should look like this:
public class BooleanToVisibilityConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
string num = value as string;
int n;
if(int.TryParse(num, out n)) { //return true is the parse worked
if(n > 10) return true;
}
return false;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}