>>>>Hi,
>>>>
>>>>I have a delete button on a WPF form which I only want enabled whenever one and only one item is selected in a grid on the same form. I figure I have to do something like this:
>>>>
>>>>IsEnabled="{Binding ElementName=grdManifest, Path=Items.Selected.Count = 1}"
>>>>
>>>>but that isn't accepted as valid code.
>>>>
>>>>Any ideas on how to do this?
>>>
>>>Implement an IValueConverter (http://msdn.microsoft.com/en-us/library/system.windows.data.ivalueconverter%28v=vs.110%29.aspx) to convert your int value (the count) to a bool. Since its a one way binding, you don't need to implement ConvertBack, just throw a NotImplementedException.
>>
>>Hi,
>>I wondered about using that approach but it's a pretty specific need and I'm fairly sure you'd still need to implement INotifyPropertyChanged so I opted for my suggestion. Can you provide a working example using valueconverter ?
>>Best,
>>Viv
>
>I forgot that SelectedItems doesn't have a dependency property associated with it, so it can't be bound directly. It can, however, be done using a data trigger:
>
>XAML:

< Window
>        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
>        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
>        xmlns:System="clr-namespace:System;assembly=mscorlib" x:Class="WpfApplication1.MainWindow"
>        xmlns:Converters="clr-namespace:WpfApplication1"
>        Title="MainWindow" Height="350" Width="525">
>    < Window.Resources>
>        < Converters:SelectedEnabledConverter x:Key="SelectedEnabledConverter" />
>    < /Window.Resources>
>    < Grid>
>        < DataGrid x:Name="grdManifest" Margin="0,0,0,43" >
>        < /DataGrid>
>        < Button Content="Delete" HorizontalAlignment="Left" Margin="119,288,0,0" VerticalAlignment="Top" Width="75" Height="22">
>            < Button.Style>
>                < Style TargetType="Button">
>                    < Style.Triggers>
>                        < DataTrigger Binding="{Binding ElementName=grdManifest, Path=SelectedItems.Count, Converter={StaticResource SelectedEnabledConverter}}" Value="false">
>                            < Setter Property="IsEnabled" Value="False" />
>                        < /DataTrigger>
>                    < /Style.Triggers>
>                < /Style>
>            < /Button.Style>
>        < /Button>
>    < /Grid>
>< /Window>
>

>
>And converter:

using System;
>using System.Collections.Generic;
>using System.Linq;
>using System.Text;
>using System.Threading.Tasks;
>using System.Windows.Data;
>
>namespace WpfApplication1
>{
>    public class SelectedEnabledConverter : IValueConverter
>    {
>        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
>        {
>            return (value as int?).GetValueOrDefault() == 1;
>        }
>
>        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
>        {
>            throw new NotImplementedException();
>        }
>    }
>}
>

OK. I think I like this better than my suggestion which required the VM to have knowledge of the View (grdManifest). Sadly, I've not been able to use WPF for a while so I'm a bit rusty - although it's still my preferred option for desktop....