Question

I have a class, called DateField, that has a string Value property. If you set this property to a string that can be parsed into a valid date, the property setter sets Value to the properly formatted date, e.g.:

    private string _Value;
    public string Value
    {
        get
        {
            return _Value;
        }
        set
        {
            if (value == _Value)
            {
                return;
            }
            object result;
            if (TryParse(value, out result))
            {
                _Value = Format(result);
            }
            else
            {
                _Value = value;
            }
            OnPropertyChanged("Value");
        }
    }

I create a TextBox that’s bound to this field:

    <DataTemplate DataType="{x:Type m:DateField}">
        <TextBox                                         
                IsTabStop="True"
                Text="{Binding Value, Mode=TwoWay, ValidatesOnDataErrors=True}">
        </TextBox>
    </DataTemplate>

When I enter, say, "010109" into this field and tab out of it, the Binding appropriately sets the Value property to this string. The property setter runs, _Value gets correctly set to "01/01/2009" (the TryParse implementation in this class is a little more catholic in what it accepts than DateTime.TryParse is), and the PropertyChanged event gets raised. I know this last bit is happening because another object that’s subscribed to the list gets updated.

But the TextBox doesn’t. Why not? I’ve set Value, I’ve raised PropertyChanged; what more do I need to be doing?

Answer 1

I think you should use a converter and implement both the Convert and the ConvertBack methods