I have a number of checkboxes that represent columns that will be shown or hidden within a Datagrid. As of now they all work except for the Check All Checkbox. When selected it should as the name suggests check all of the checkboxes within the group.

None of these checkboxes are tied to a View Model, they only affect the appearance of the data on the View itself. One solution could be to implement all the checkboxes on the ViewModel and then take the Check All command and set all the flags to true. I'm just not fond of the idea because I'm adding 20 properties and various commands etc all JUST to support this one thing.

I had some ideas possibly using "IsThreeState" attribute but nothing cohesive. I'm not against rendering them in a different container either, I'm just not certain that it helps.

```
<Expander  DockPanel.Dock="Top" Header="{x:Static p:Resources.shSettings}" IsExpanded="True">
            <DockPanel> 
                <GroupBox Header="Filter Columns" DockPanel.Dock="Right">
                    <ag:AutoGrid Columns="150, 150, 150" RowCount="7" RowHeight="20">
                        <CheckBox Content="Check All" />
                        <CheckBox Content="Co. Name" x:Name="filterCoName" />
                        <CheckBox Content="Rating" x:Name="filterRating" />

                        <CheckBox Content="Severity (!)" x:Name="filterSeverity" />
                        <CheckBox Content="Stn ID" x:Name="filterStation" />
                        <CheckBox Content="MB" x:Name="filterMB" />

                        <CheckBox Content="New" x:Name="filterNew" />
                        <CheckBox Content="KV" x:Name="filterKV" />
                        <CheckBox Content="STE Rating" x:Name="filterSiteRating" />

                        <CheckBox Content="QCA" x:Name="filterQCA" />
                        <CheckBox Content="Area" x:Name="filterArea" />
                        <CheckBox x:Name="filterDuration" Content="Duration" />

                        <CheckBox Content="Plan in Place" x:Name="filterPIP"  />
                        <CheckBox Content="Type" x:Name="filterType" />
                        <CheckBox Content="Rating(%)" x:Name="filterRatingPercent" />

                        <CheckBox Content="ID" x:Name="filterId" />
                        <CheckBox Content="Pre" x:Name="filterPre" />
                        <CheckBox Content="Deviation" x:Name="filterDeviation" />

                        <CheckBox Content="Status" x:Name="filterStatus" />
                        <CheckBox Content="Post" x:Name="filterPost" />
                        <CheckBox Content="Description" x:Name="filterDescription" />
                    </ag:AutoGrid>
                </GroupBox>
            </DockPanel>
        </Expander>

```