Accessing a collection within a collection List Xamarin xaml

Question

I am using xamarin forms and using a collection within a collection my question is how do I bind to my lines when I use the ViewModel pattern.

I am using telerik data grid for the task, which can take any binding object as its Item Source. So my question is how do I access my sub list.

At the min I am doing ItemsSource="{Binding Boms}"

Can't I just do ItemsSource="{Binding Boms.Lines}" when I try that I just get blank results.

<telerikGrid:RadDataGrid x:Name="gridItems" IsVisible="False" SelectionMode="Single"
                         SelectionChanged="GridItems_SelectionChanged" ItemsSource="{Binding Boms}"
                         AutoGenerateColumns="False">
    <telerikGrid:RadDataGrid.Columns>
        <telerikGrid:DataGridTextColumn PropertyName="Name"  HeaderText="Name" />
        <telerikGrid:DataGridTextColumn PropertyName="Qty" HeaderText="Qty" />
        <telerikGrid:DataGridTemplateColumn x:Name="Actions" HeaderText="Scan Item">
            <telerikGrid:DataGridTemplateColumn.CellContentTemplate>
                <DataTemplate>
                    <telerikInput:RadButton 
                        Grid.Row="0" Grid.Column="1" HeightRequest="40" Text="Scan Item" x:Name="btnScanItem"
                        Margin="0, 2, 0, 0" VerticalOptions="StartAndExpand" HorizontalOptions="Center" 
                        BackgroundColor="Black" TextColor="White" />

                </DataTemplate>
            </telerikGrid:DataGridTemplateColumn.CellContentTemplate>
        </telerikGrid:DataGridTemplateColumn>
        <telerikGrid:DataGridTemplateColumn x:Name="Edit" HeaderText="Edit Item">
            <telerikGrid:DataGridTemplateColumn.CellContentTemplate>
                <DataTemplate>
                    <telerikInput:RadButton 
                        Grid.Row="0" Grid.Column="1" HeightRequest="40" Text="Edit Item" Clicked="BtnScanItem_Clicked"
                        x:Name="btnScanItem" Margin="0, 2, 0, 0" VerticalOptions="StartAndExpand"
                        HorizontalOptions="Center" 
                        BackgroundColor="Black" TextColor="White" />

                </DataTemplate>
            </telerikGrid:DataGridTemplateColumn.CellContentTemplate>
        </telerikGrid:DataGridTemplateColumn>
    </telerikGrid:RadDataGrid.Columns>

</telerikGrid:RadDataGrid>

My Code Behind

    public class StockScanDataStore : IScanDataStore<Bom>
    {
        List<Bom> bomItems;
        public StockScanDataStore()
        { 
            bomItems = new List<Bom>();
            var mockItems = new List<Bom>
            {
                new Bom { BomId =1,Name="Knee operations",Quantity=20,Operations=10 },
                new Bom { BomId =1,Name="Back operations",Quantity=20,Operations=10 }
                ,

                new Bom { BomId =1,Name="Steal Plate",Quantity=20,Operations=10,
                Lines = new List<BomDetail>()            {
                new BomDetail{ BomId=1,Name="Screw",Qty=20} ,
                new BomDetail{ BomId=2,Name="Plate",Qty=10 },
                new BomDetail{ BomId=3,Name="Screw",Qty=5 }
                }
            } };

            foreach (var item in mockItems)
            {
                bomItems.Add(item);
            }



    }

My Code Behind I set my view model as such

    ScanTransViewModel viewModel;

    public StockTransfer()
    {
      InitializeComponent();
      BindingContext = viewModel = new ScanTransViewModel();
    }

My model is:

    public class Bom
    {
        public long BomId { get; set; }
        public long BOMLineID { get; set; }
        public long StockItemID { get; set; }
        public string BomLineType { get; set; }
        public decimal? Quantity { get; set; }
        public long UnitID { get; set; }
        public decimal? MultipleOfBaseUnit { get; set; }
        public string Code { get; set; }
        public string Name { get; set; }
        public string Barcode { get; set; }
        public long ProductGroupID { get; set; }
        public string ProductGroupCode { get; set; }
        public decimal Operations { get; set; }

        public List<BomDetail> Lines { get; set; }
        public override string ToString()
        {
            return Code;
        }
    }

Answer 1

It looks like, in your code-behind, that you set the BindingContext AFTER InitializeContext(). Since I see no code that forces the view to update, I assume the problem is that the view inits as blank and then the list updates without the view following suit.

In your situation, I would try adding INotifyPropertyChanged interface to your code-behind. Then update your List like so -

        protected virtual void NotifyPropertyChanged([CallerMemberName]string propertyName = null)
        {
            if (propertyName != null)
                OnPropertyChanged(propertyName);
        }

        private List<Bom> _bomItems= new List<Bom>();
        public List<IBlePeripheral> BomItems
        {
            get { return _bomItems; }
            set
            {
                _bomItems= value;
                NotifyPropertyChanged();

                IsEmptyList = value.Count < 1;
            }
        }