从DataGridTextColumn.HeaderTemplate复选框设置DataGridTextColumn IsReadonly属性

Question

I have WPF DataGrid, where I am displaying some data. I need to provide an option for the user to edit the data, if he/she checks the checkbox in the header. Here is the WPF part I have done.

<DataGrid.Columns>
    <DataGridTextColumn Header="MaxLength" Binding="{Binding MaxLength}">
        <DataGridTextColumn.HeaderTemplate>
            <DataTemplate>
                <CheckBox x:Name="AAOverride" Content="Increase Max Length" />
            </DataTemplate>
        </DataGridTextColumn.HeaderTemplate>
    </DataGridTextColumn>
</DataGrid.Columns>

I would like to enable / disable the MaxLength Column, based on user selection. I am following MVVM, so codebehind option I don't have :(

Answer 1

Just to a RelativeSource binding to get to your root view-model. Something like this, I suppose (also needs an IValueConverter to negate the bool for "increase max length" -> "read only"):

<DataGrid.Columns>
    <DataGridTextColumn Header="MaxLength" Binding="{Binding MaxLength}"
        IsReadOnly="{Binding 
            RelativeSource={RelativeSource AncestorType=DataGrid},
            Path=DataContext.IsMaxLengthEnabled,
            Converter={StaticResource NegateBool}}">
        <DataGridTextColumn.HeaderTemplate>
            <DataTemplate>
                <CheckBox x:Name="AAOverride" Content="Increase Max Length" 
                    IsChecked="{Binding RelativeSource={RelativeSource AncestorType=DataGrid},
                                Path=DataContext.IsMaxLengthEnabled,
                                Mode=TwoWay}"
                 />
            </DataTemplate>
        </DataGridTextColumn.HeaderTemplate>
    </DataGridTextColumn>
</DataGrid.Columns>