Disabling button in bottom row in a wpf datagrid

Question

I have a DataGrid with 4 columns, the first two of them are bound to an object. The other two are button columns are made like this

<DataGridTemplateColumn  MaxWidth="100" Header="Delete">
    <DataGridTemplateColumn.CellTemplate>
        <DataTemplate>
            <Button Name="BtnDelete" CommandParameter="{Binding Path=Id}" Content="Delete" Click="BtnDeleteEmployee_Click" />
        </DataTemplate>
    </DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>

My Datagrid has CanUserAddRows="True" which always generates an empty row in the bottom of the grid. However, I would like the two buttons on the bottom row to be disabled until the other rows have been filled. As it is now, I'm (of course) getting a nullreferenceexception when I click the button.

I guess a solution would be to bind the button's IsEnabled property to

id>0

But how to do this, I am not sure.

Magnus Johansson Magnus Johansson · Accepted Answer · 2012-05-29T09:32:25

One way to accomplish this is to bind the IsEnabled property to the Id property and use a ValueConverter to retun True or False based on your criteria.

A value converter could look like this:

public class IdToEnabledConverter:IValueConverter
{
  public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
  {
    return value != null && (int)value > 0;
  }

  public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
  {
    throw new NotImplementedException();
  }
}

and you reference it in your resources section:

<Grid.Resources>
  <local:IdToEnabledConverter x:Key="IdToEnabledConverter"/>
</Grid.Resources>

And bind the IsEnabled property:

<Button IsEnabled="{Binding Id, Converter={StaticResource IdToEnabledConverter}}"/>

Disabling button in bottom row in a wpf datagrid

3 Answers