WPF binding not working properly with properties of int type

WPF binding not working properly with properties of int type

I am having a property of int type in my view model which is bound to a TextBox. Everything works properly, TwoWay binding works fine except in one case -

If I clear the value of TextBox, property setter doesn't gets called and although value is cleared in TextBox, property still holds the previous value.

has anyone faced similar issue? is there any workaround for this?

Here is the property -

public int MaxOccurrences {     get     {         return this.maxOccurrences;     }     set     {         if (this.maxOccurrences != value)         {             this.maxOccurrences = value;             base.RaisePropertyChanged("MaxOccurrences");         }     } } 

Here is how I am binding the property in xaml -

<TextBox Text="{Binding Path=MaxOccurrences, Mode=TwoWay,      NotifyOnSourceUpdated=True, UpdateSourceTrigger=PropertyChanged}"      HorizontalAlignment="Center" Width="30" Margin="0,0,5,0"/> 

Answers & Comments...

Answer: 1

This is partially a guess (I haven't got VS handy right now to try it out), but I think it's because a cleared text box is an empty string (""), which can't be implicitly converted to an int. You should probably implemented a type converter to provide the conversion for you. (you probably want to do something like convert "" to 0)

by : Simon P Stevenshttp://stackoverflow.com/users/119738

Answer: 2

It's because an int value can't be null. It's best to use a string property that converts the value for you within your code to the required int property field.

That way you can perform a

if(string.IsNullOrEmpty(text)) {   this.intValue = 0; } 

by : ChrisBDhttp://stackoverflow.com/users/102238

Answer: 3

I had the similar problem.

You just need to update the code as:

<TextBox Text="{Binding Path=MaxOccurrences, Mode=TwoWay, TargetNullValue={x:Static sys:String.Empty}, NotifyOnSourceUpdated=True,  UpdateSourceTrigger=PropertyChanged}"   HorizontalAlignment="Center" Width="30" Margin="0,0,5,0"/>  

by : WPF Userhttp://stackoverflow.com/users/355820

Answer: 4

Akjoshi, I have a working solution! You need to change your integer property to Naullable (i.e. int? ), see the following snippet:

private int? _maxOccurrences; public int? MaxOccurrences {     get { return _maxOccurrences; }     set { _maxOccurrences = value; } } 

You also need to add a value converter to convert the empty string to null value, see the following code snippet:

public class EmptyStringToNullConverter : IValueConverter {     #region IValueConverter Members      public object Convert(object value, Type targetType, object parameter, CultureInfo culture)     {         return value;     }      public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)     {         return value == null || string.IsNullOrEmpty(value.ToString())             ? null             : value;     }