Tabs not showing when adding them through method - wpf

Question

I have a datagrid. I want to add Tab when row double click event is rised. When AddTab method is called Tab is added to ObservableCollection, but it doesn't show up on TabControl. Why it doesn't show up? Because there is a wrong DataContext when method called?
<DataGrid helpers:RowDoubleClickHandler.MethodName="AddTab" AutoGenerateColumns="False"
IsSynchronizedWithCurrentItem="True" CanUserResizeRows="True" x:Name="dataGrid1"
ItemsSource="{Binding DataGridEntries3}" HorizontalContentAlignment="Stretch"
VerticalContentAlignment="Stretch" IsReadOnly="True">
AddTab method in ViewModel
public void AddTab()
{
Tabs.Add(new TabEntry
{
Description = "Tab3",
DataGridEntries = new ObservableCollection<DataGridEntry>()
{
new DataGridEntry()
{
}
}
});
XAML with TabControl
<Window x:Class="ProjectZero.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vm="clr-namespace:ProjectZero"
Title="MainWindow" Height="350" Width="525" DataContext="{Binding RelativeSource={RelativeSource Self}}">
<Window.Resources>
<vm:MainViewModel x:Key="ViewModel"/>
</Window.Resources>
<Grid>
<ToolBar Height="40" VerticalAlignment="Top">
<Menu>
<MenuItem Header="Menu" Margin="6" Foreground="White" FontSize="14" FontFamily="Times New Roman">
<MenuItem Header="Add Invoice" Command="{Binding AddInvoice}"/>
<MenuItem Header="Invoices List" Command="{Binding AddInvoiceList}" FontFamily="Tahoma" />
</MenuItem>
<Menu.Background>
<SolidColorBrush />
</Menu.Background>
</Menu>
<ToolBar.Background>
<LinearGradientBrush EndPoint="1,0.5" StartPoint="0,0.5">
<GradientStop Color="Black" Offset="0" />
<GradientStop Color="#FF173ADE" Offset="0.431" />
<GradientStop Color="#FF0B1D6F" Offset="0.646" />
</LinearGradientBrush>
</ToolBar.Background>
</ToolBar>
<TabControl x:Name="tabControl1" SelectedItem="{Binding SelectedItem}" ItemsSource="{Binding Tabs}" ItemTemplate="{DynamicResource DataTemplateType1}" TabStripPlacement="Top" HorizontalAlignment="Stretch" Margin="10,46,0,0" VerticalAlignment="Stretch" Width="Auto">
</TabControl>
ViewModel for Tabs
public class MainViewModel : BaseViewModel
{
public RelayCommand RelayCommand { get; set; }
public MainViewModel()
{
this.RelayCommand = new RelayCommand(this);
Tabs.CollectionChanged += (o, e) =>
{
if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add)
{
foreach (BaseViewModel item in e.NewItems)
if (item.MyType == "TabEntry")
DataGridEntries3.Add(item as TabEntry);
}
};
var t = (from i in Tabs where i.MyType == "TabEntry" select (TabEntry)i);
DataGridEntries3 = new ObservableCollection<TabEntry>(t);
}
private ObservableCollection<BaseViewModel> _tabs;
public ObservableCollection<BaseViewModel> Tabs
{
get { return _tabs != null ? _tabs : _tabs = new ObservableCollection<BaseViewModel>(); }
set { _tabs = value; OnPropertyChanged("Tabs"); }
}
BaseViewModel _SelectedItem;
public BaseViewModel SelectedItem
{
get { return _SelectedItem; }
set { _SelectedItem = value; OnPropertyChanged("SelectedItem"); }
}
private ObservableCollection<TabEntry> _DataGridEntries3;
public ObservableCollection<TabEntry> DataGridEntries3
{
get { return _DataGridEntries3 != null ? _DataGridEntries3 : _DataGridEntries3 = new ObservableCollection<TabEntry>(); }
set { _DataGridEntries3 = value; OnPropertyChanged("DataGridEntries3"); }
}
ICommand _AddInvoice = null;
ICommand _AddInvoiceList = null;
public ICommand AddInvoice
{
get
{
return _AddInvoice != null ? _AddInvoice : _AddInvoice.SetCommand(param =>
{
Tabs.Add(new TabEntry
{
Description = "Tab3",
DataGridEntries = new ObservableCollection<DataGridEntry>()
{
new DataGridEntry()
{
}
}
});
});
}
}
public ICommand AddInvoiceList
{
get
{
return _AddInvoiceList != null ? _AddInvoiceList : _AddInvoiceList.SetCommand(param =>
{
var tab_dc = Tabs.FirstOrDefault(it => it.GetType() == typeof(MainViewModel));
if (tab_dc != null)
{
Tabs.Add(tab_dc);
}
else
{
var new_tab = new MainViewModel();
Tabs.Add(new_tab);
}
});
}
}
}
Also here is RowDoubleClick Event Handler
public sealed class RowDoubleClickHandler : FrameworkElement
{
public RowDoubleClickHandler(DataGrid dataGrid)
{
MouseButtonEventHandler handler = (sender, args) =>
{
var row = sender as DataGridRow;
if (row != null && row.IsSelected)
{
var methodName = GetMethodName(dataGrid);
var dataContextType = dataGrid.DataContext.GetType();
var method = dataContextType.GetMethod(methodName);
if (method == null)
{
throw new MissingMethodException(methodName);
}
method.Invoke(dataGrid.DataContext, null);
}
};
dataGrid.LoadingRow += (s, e) =>
{
e.Row.MouseDoubleClick += handler;
};
dataGrid.UnloadingRow += (s, e) =>
{
e.Row.MouseDoubleClick -= handler;
};
}
public static string GetMethodName(DataGrid dataGrid)
{
return (string)dataGrid.GetValue(MethodNameProperty);
}
public static void SetMethodName(DataGrid dataGrid, string value)
{
dataGrid.SetValue(MethodNameProperty, value);
}
public static readonly DependencyProperty MethodNameProperty = DependencyProperty.RegisterAttached(
"MethodName",
typeof(string),
typeof(RowDoubleClickHandler),
new PropertyMetadata((o, e) =>
{
var dataGrid = o as DataGrid;
if (dataGrid != null)
{
new RowDoubleClickHandler(dataGrid);
}
}));
}

Answer 1

A few tips, since you asked in your comment:
This:
private ObservableCollection<BaseViewModel> _tabs;
public ObservableCollection<BaseViewModel> Tabs
{
get { return _tabs != null ? _tabs : _tabs = new ObservableCollection<BaseViewModel>(); }
set { _tabs = value; OnPropertyChanged("Tabs"); }
}
Could be rewritten a lot cleaner as:
public ObservableCollection<BaseViewModel> Tabs { get; private set; }
With this added to your constructor:
Tabs = new ObservableCollection<BaseViewModel>();
This is a consistent theme in your code. Basically, don't make modifications in your property getters/setters unless you really really need to. And in your case, all it is doing is complicating things.
It is especially confusing when you have a getter that then will add a tab to your collection of tabs when first invoked. That is very difficult to follow programmatically. Just do your initialization in your constructor like everyone else does :)