Xamarin.Forms (PRISM) - Bind checkbox, to a command in viewmodel, outside listview itemsource

Question

Sooo, im building a Prism, xamarin.forms app.

I have a object by the name of "Herd", with basic attributes.

Im displaying a list of these objects, and want to activate a command that sends the herd that is checked in a checkbox to the viewmodel.

<ListView
                x:Name="UpdateHerdList"
                ItemsSource="{Binding HerdsThatsNeedsToBeUpdated}"
                RowHeight="60"
                >
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <CustomRenderer:TransparentViewCell>
                            <Grid
                               >
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="1*"/>
                                    <ColumnDefinition Width="50"/>
                                </Grid.ColumnDefinitions>
                                <Label 
                                    TextColor="Black"
                                    FontSize="15"
                                    VerticalTextAlignment="Center"
                                    HorizontalTextAlignment="Start"
                                    Grid.Column="0"
                                    Text="{Binding HeaderName}"
                                    />
                                    <CheckBox 
                                        Grid.Column="1"
                                        HorizontalOptions="Center" 
                                        ScaleX="1.75" 
                                        ScaleY="1.75"
                                        Color="Black"
                                        IsChecked="True"
                                        >
                                        <CheckBox.Behaviors>
                                            <b:EventToCommandBehavior
                                                EventName="PropertyChanged"
                                                Command="{Binding UpdateThisHerdCommand}"
                                                CommandParameter="{Binding Herd}"
                                                />
                                        </CheckBox.Behaviors>
                                    </CheckBox>
                                </Grid>
                        </CustomRenderer:TransparentViewCell>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>

But i cant seem to find the right way to bind to the viewmodel inside the itemsource of the listview.

Can someone please help guiding me to the right binding.

Thanks in advance!

Answer 1

About binding one command to checkbox, I do one sample that you can see the following code. If you change checkbox checked, will pass current listview item.

 <ListView
            x:Name="UpdateHerdList"
            ItemsSource="{Binding HerdsThatsNeedsToBeUpdated}"
            RowHeight="60">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <Grid>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="1*" />
                                <ColumnDefinition Width="50" />
                              
                            </Grid.ColumnDefinitions>
                            <Label
                                Grid.Column="0"
                                FontSize="15"
                                HorizontalTextAlignment="Start"
                                Text="{Binding HeaderName}"
                                TextColor="Black"
                                VerticalTextAlignment="Center" />
                            <CheckBox
                                Grid.Column="1"
                                HorizontalOptions="Center"
                                IsChecked="True"
                                ScaleX="1.75"
                                ScaleY="1.75"
                                Color="Black">

                                <CheckBox.Behaviors>
                                    <b:EventToCommandBehavior
                                        Command="{Binding BindingContext.UpdateThisHerdCommand, Source={x:Reference UpdateHerdList}}"
                                        CommandParameter="{Binding .}"
                                        EventName="CheckedChanged" />
                                </CheckBox.Behaviors>
                            </CheckBox>
                          
                        </Grid>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

public partial class Page34 : ContentPage
{
    public ObservableCollection<Herd> HerdsThatsNeedsToBeUpdated { get; set; }
    public ICommand UpdateThisHerdCommand { get; set; }
    public Page34()
    {
        InitializeComponent();

        HerdsThatsNeedsToBeUpdated = new ObservableCollection<Herd>()
        {
            new Herd(){HeaderName="test 1"},
            new Herd(){HeaderName="test 2"},
            new Herd(){HeaderName="test 3"},
            new Herd(){HeaderName="test 4"},
            new Herd(){HeaderName="test 5"},
            new Herd(){HeaderName="test 6"}

        };

        UpdateThisHerdCommand = new Command<Herd>(checkboxcommand);

        this.BindingContext = this;
    }

    private void checkboxcommand(Herd herd)
    {
        Console.WriteLine("the selected item is {0}",herd.HeaderName);
    }
}

public class Herd
{
    public string HeaderName { get; set; }
}