WPF binding not working properly with properties of int type

Question

Hi,

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

If i clear the value of text box, property setter doesn't gets called and although value is cleared in text box, 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"/>

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)

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;
}

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"/>