How to bind DataGridColumn.Visibility?

Question

I have an issue similar to the following post:

Silverlight DataGridTextColumn Binding Visibility

I need to have a Column within a Silverlight DataGrid be vis

Answer 1

From your MyDataGridTextColumn class, you could get the surrounding DataGrid. Then you get your ViewModel out of the DataContext of the DataGrid and add a handler to the PropertyChanged event of your ViewModel. In the handler you just check for the property name and its value and change the Visibility of the Column accordingly. Its not quite the best solution, but it should work ;)

Answer 2

Here's the solution I've come up with using a little hack.

First, you need to inherit from DataGrid.

public class DataGridEx : DataGrid
{
    public IEnumerable<string> HiddenColumns
    {
        get { return (IEnumerable<string>)GetValue(HiddenColumnsProperty); }
        set { SetValue(HiddenColumnsProperty, value); }
    }

    public static readonly DependencyProperty HiddenColumnsProperty =
        DependencyProperty.Register ("HiddenColumns", 
                                     typeof (IEnumerable<string>), 
                                     typeof (DataGridEx),
                                     new PropertyMetadata (HiddenColumnsChanged));

    private static void HiddenColumnsChanged(object sender,
                                             DependencyPropertyChangedEventArgs args)
    {
        var dg = sender as DataGrid;
        if (dg==null || args.NewValue == args.OldValue)
            return;

        var hiddenColumns = (IEnumerable<string>)args.NewValue;
        foreach (var column in dg.Columns)
        {
            if (hiddenColumns.Contains ((string)column.GetValue (NameProperty)))
                column.Visibility = Visibility.Collapsed;
            else
                column.Visibility = Visibility.Visible;
        }
    }
}

The DataGridEx class adds a new DP for hiding columns based on the x:Name of a DataGridColumn and its descendants.

To use in your XAML:

<my:DataGridEx x:Name="uiData"
               DataContext="{Binding SomeDataContextFromTheVM}"
               ItemsSource="{Binding Whatever}"
               HiddenColumns="{Binding HiddenColumns}">
    <sdk:DataGridTextColumn x:Name="uiDataCountOfItems">
                            Header="Count"
                            Binding={Binding CountOfItems}"
    </sdk:DataGridTextColumn>
</my:DataGridEx>

You need to add these to your ViewModel or whatever data context you use.

private IEnumerable<string> _hiddenColumns;
public IEnumerable<string> HiddenColumns
{
    get { return _hiddenColumns; }
    private set
    {
        if (value == _hiddenColumns)
            return;

        _hiddenColumns = value;
        PropertyChanged (this, new PropertyChangedEventArgs("HiddenColumns"));
    }
}

public void SomeWhereInYourCode ()
{
    HiddenColumns = new List<string> {"uiDataCountOfItems"};
}

To unhide, you only need to remove the corresponding name from the list or recreate it without the unhidden name.

Answer 3

Chris Mancini,

you do not create binding to "Binding" property of data grid column. Well, you write "{Binding User.UserName}", but it doesn't create binding, because (as zachary said) datagrid column doesn't inherit from FrameworkElement and hasn't SetBinding method. So expression "{Binding User.UserName}" simply creates Binding object and assign it to Binding property of column (this property is type of Binding). Then datagrid column while generates cells content (GenerateElement - protected method) uses this Binding object to set binding on generated elements (e.g. on Text property of generated TextBlock) which are FrameworkElements