WPF MVVM Light enabling button if data grid row is selected

Question

I can't seem to find a straight answer on this anywhere. I have a button that I want to Disable UNTIL a DataGrid row is selected. Doesn't matter which row. Once it's deselected I would like it to be disabled again.

Answer 1

here you go

<StackPanel>
    <DataGrid x:Name="dGrid">
        <DataGrid.Columns>
            <DataGridTextColumn Binding="{Binding}"
                                Header="A Column" />
        </DataGrid.Columns>
        <sys:String>item 1</sys:String>
        <sys:String>item 2</sys:String>
        <sys:String>item 3</sys:String>
        <sys:String>item 4</sys:String>
    </DataGrid>
    <Button x:Name="button"
            Content="A Button">
        <Button.Style>
            <Style TargetType="Button">
                <Style.Triggers>
                    <DataTrigger Binding="{Binding SelectedItems.Count,ElementName=dGrid}"
                                 Value="0">
                        <Setter Property="IsEnabled"
                                Value="False" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Button.Style>
    </Button>
</StackPanel>

above example will place a trigger on SelectedItems.Count of DataGrid and will disable the button if it is zero

this is a pure xaml solution, other solution may also be possible with converters or vm properties

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EDIT

as requested here is a sample to do it without using Name attribute

<StackPanel>
    <DataGrid>
        <DataGrid.Columns>
            <DataGridTextColumn Binding="{Binding}"
                                Header="A Column" />
        </DataGrid.Columns>
        <sys:String>item 1</sys:String>
        <sys:String>item 2</sys:String>
    </DataGrid>
    <Button Content="A Button">
        <Button.Style>
            <Style TargetType="Button">
                <Style.Triggers>
                    <DataTrigger Binding="{Binding Parent.Children[0].SelectedItems.Count,RelativeSource={RelativeSource Self}}"
                                 Value="0">
                        <Setter Property="IsEnabled"
                                Value="False" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Button.Style>
        </Button>
</StackPanel>

above code assume the datagrid to be the first child of the parent container Parent.Children[0], you may adjust it as per your needs.