How to code a UWP MVVM ComboBox within an ItemTemplate? - mvvm

Question

I'm trying to figure out how to display a category for a selected item in a ComboBox which is itself within a GridView.ItemsTemplate. Nothing that I have tried so far has worked. I've tried using SelectedValue and SelectedValuePath.
I can display the Item's Category in a textbox from within the GridView.ItemsTemplate, but not the collection in a ComboBox.
// FiledNotesPageViewModel ViewModel
public class FiledNotesPageViewModel : ViewModelBase
{
public ObservableCollection<MemoryItem> NoteItems { get; set; } = new ObservableCollection<MemoryItem>();
}
// Public Properties
public int FiledNotesId
{
get
{
return _filedNotesId;
}
set
{
_filedNotesId = value;
OnPropertyChanged("FiledNotesId");
}
}
public string Name
{
get
{
return _name;
}
set
{
_name = value;
OnPropertyChanged("Name");
}
}
public string Note
{
get
{
return _note;
}
set
{
_note = value;
OnPropertyChanged("Note");
}
}
public string Category
{
get
{
return _category;
}
set
{
_category = value;
OnPropertyChanged("Category");
}
}
// MemoryItem Model
public int FiledNotesId { get; set; }
public string Note { get; set; }
public string Name { get; set; }
public string Category { get; set; }
FiledNotesPage View
<GridView x:Name="FiledNotesGrid"
RelativePanel.Below="FilterNoteGrid"
ItemsSource="{x:Bind ViewModel.NoteItems}">
<GridView.ItemsPanel>
<ItemsPanelTemplate>
<ItemsWrapGrid Orientation="Horizontal"
Margin="5"/>
</ItemsPanelTemplate>
</GridView.ItemsPanel>
<GridView.ItemTemplate>
<DataTemplate x:DataType="data:MemoryItem">
<StackPanel Orientation="Vertical"
BorderBrush="{ThemeResource AppBarBorderThemeBrush}"
BorderThickness="2,2,2,4"
Margin="20"
Background="#FFF7F713" >
<TextBox x:Name="NoteNameTextBox"
Text="{x:Bind Name, Mode=TwoWay}"/>
<TextBox x:Name="NoteTextBox"
TextWrapping="Wrap"
AcceptsReturn="True"
Text="{x:Bind Note, Mode=TwoWay}"/>
<StackPanel Orientation="Horizontal">
<TextBlock Margin="5,0">Category:</TextBlock>
<ComboBox x:Name="NoteCategoryComboBox"
SelectedItem="{Binding FiledNotesId, Mode=TwoWay}"
MinWidth="125">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Category}" />
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
</StackPanel>
</StackPanel>
</DataTemplate>
</GridView.ItemTemplate>
</GridView>

Answer 1

Your combobox doesn't have an ItemsSource
You need to do something like this...
In your CS File create an ObservableCollection property to bind to.
public ObservableCollection<int> FieldNoteIds {get; set;}
In your view, bind to your collection
<ComboBox ItemsSource="{Binding FieldNoteIds}">
Right now you're providing a template for how to display each item that is populated into the combobox but you're not giving it anything to populate.
MSDN Tutorial on ComboBoxes and Binding
https://code.msdn.microsoft.com/windowsdesktop/Best-ComboBox-Tutorial-5cc27f82#content