TwoWay Binding MySettings to DataGrid Column Width

Question

I am trying to bind the width of my columns within a DataGrid to an application settings property. I have this working when binding is set to OneWay mode however, I need the setting to be updated based on the width of the column when the app closes. When I change the binding mode to TwoWay, the binding breaks all together. My code is below, how can I go about achieving this?

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Extension Class

Public Class SettingBindingExtension
    Inherits Binding

    Public Sub New()
        Initialize()
    End Sub

    Public Sub New(ByVal path As String)
        MyBase.New(path)
        Initialize()
    End Sub

    Private Sub Initialize()
        Me.Source = MySettings.[Default]

        'OneWay mode works for the initial grid load but any resizes are unsaved.
        Me.Mode = BindingMode.OneWay

        'using TwoWay mode below breaks the binding...
        'Me.Mode = BindingMode.TwoWay
    End Sub

End Class

xaml

xmlns:w="clr-namespace:Stack"

<DataGrid>
...
    <DataGridTextColumn Header="STACK" 
                        Width="{w:SettingBinding StackColumnWidth}"/>
...
</DataGrid>

Benoit Catherinet Benoit Catherinet · Accepted Answer · 2013-09-17T13:04:30

The problem is that Width is of type DataGridLength and there is no default converter back to double so you will need to create your own converter to do that, here is an example of converter which should work:

class LengthConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        DataGridLengthConverter converter=new DataGridLengthConverter();
        var res = converter.ConvertFrom(value);
        return res;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        DataGridLength length = (DataGridLength)value ;
        return length.DisplayValue;
    }
}

TwoWay Binding MySettings to DataGrid Column Width

3 Answers