There is a list with Checkboxes, how to click on the button to mark / unmark all Checkboxes?

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1 answer 1

It seems nothing complicated - bindings, commands ...

Suppose I have such a VM, representing one list item:

class ItemVm : Vm { string name; public string Name { get => name; set => Set(ref name, value, nameof(Name)); } bool isChecked; public bool IsChecked { get => isChecked; set => Set(ref isChecked, value, nameof(IsChecked)); } }

And the main VM contains a collection of such elements and commands to mark or unmark all the elements:

 class MainVM : Vm { public List<ItemVm> Items { get; } public ICommand CheckAllCommand { get; } public ICommand UncheckAllCommand { get; } public MainVM() { Items = new List<ItemVm> { new ItemVm { Name = "Молоко" }, new ItemVm { Name = "Творог" }, new ItemVm { Name = "Сметана" }, new ItemVm { Name = "Кефир" }, new ItemVm { Name = "Сыр" } }; CheckAllCommand = new DelegateCommand( _ => Items.ForEach(item => item.IsChecked = true)); UncheckAllCommand = new DelegateCommand( _ => Items.ForEach(item => item.IsChecked = false)); } }

Markup:

 <Grid Margin="5"> <Grid.RowDefinitions> <RowDefinition/> <RowDefinition Height="Auto"/> </Grid.RowDefinitions> <ItemsControl ItemsSource="{Binding Items}"> <ItemsControl.ItemTemplate> <DataTemplate> <CheckBox Content="{Binding Name}" IsChecked="{Binding IsChecked}"/> </DataTemplate> </ItemsControl.ItemTemplate> </ItemsControl> <UniformGrid Grid.Row="1" Rows="1" Margin="0,5,0,0"> <Button Content="Check all" Margin="0,0,2.5,0" Command="{Binding CheckAllCommand}"/> <Button Content="Uncheck all" Margin="2.5,0,0,0" Command="{Binding UncheckAllCommand}"/> </UniformGrid> </Grid>

checkAll.gif

If you want to use one CkeckBox instead of two buttons, you can get by with one command that takes a parameter:

 CheckAllCommand = new DelegateCommand( o => Items.ForEach(item => item.IsChecked = (bool)o));

then you just need to pass a parameter to the command - the current state of the flag:

 <CheckBox Content="Check all" Command="{Binding CheckAllCommand}" CommandParameter="{Binding IsChecked, RelativeSource={RelativeSource Self}}"/>

But I did not do this option, because You didn’t describe whether this general checkbox needs to somehow react to setting / clearing checkboxes in the list manually one by one.