No data with ListBox with Grid inside - xaml

I am doing a Grid of two columns that are inside a ListBox. That after that I can DataBind the two columns to be repeated vertically.
So far the code below shows nothing on the WP7 emulator.
<ListBox Background="Yellow" ItemsSource="{Binding}" Height="100" Margin="0,0,8,0">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid Height="100">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="200" />
<ColumnDefinition Width="200" />
</Grid.ColumnDefinitions>
<TextBlock Text="Channels" HorizontalAlignment="Stretch" Foreground="Black" Grid.Column="0" />
<TextBlock Text="Antenna" HorizontalAlignment="Stretch" Foreground="Black" Grid.Column="1"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Please help me.

If your only concern is that you see ItemTemplate in action, you can supply explicit non-UI items as follows:
<ListBox Background="Yellow" Height="100" Margin="0,0,8,0" xmlns:sys="clr-namespace:System;assembly=mscorlib">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid Height="30">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="200" />
<ColumnDefinition Width="200" />
</Grid.ColumnDefinitions>
<TextBlock Text="Channels" HorizontalAlignment="Stretch" Foreground="Black" Grid.Column="0" />
<TextBlock Text="Antenna" HorizontalAlignment="Stretch" Foreground="Black" Grid.Column="1"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
<sys:String>1111111</sys:String>
<sys:String>2222222</sys:String>
<sys:String>3333333</sys:String>
</ListBox>
Notes:
I removed ItemsSource and supplied items explicitly.
Items must not derive from UIElement so that they are templated. (UIElements are simply drawn and the template is ignored.)
I added System namespace so that string objects can be specified.
I decreased ItemTemplate height so that more than one list row is visible.
Easier solution:
Give the ListBox a name and remove the binding:
<ListBox x:Name="myLB" Background="Yellow" Height="100" Margin="0,0,8,0">
Then use this line in the code (after the call InitializeComponent()):
myLB.ItemsSource = new List<string> { "First", "Second", "Third" };

If you want design-time itemssource, you can use the IsInDesignMode property like so:
if (System.ComponentModel.DesignerProperties.IsInDesignTool)
{
myListBox.ItemsSource = GenerateMockItems();
}
else
{
myListBox.ItemsSource = GetRealItems();
}
in MVVMLight ViewModels, this is shortcut-ed as
if (IsInDesignMode)
{
}
Similarly, since it looks like you're setting your ItemsSource in xaml, inside your class that is your DataContext, you could do something like
public class MyViewModel
{
public MyViewModel()
{
if (System.ComponentModel.DesignerProperties.IsInDesignTool)
{
Items = GenerateMockItems();
EditTime = GenerateRandomFutureDate();
}
else
{
//whatever you expect should happen in runtime
}
}
//what list is binding to
public ObservableCollection<Item> Items { get; set; }
//other properties.. for example
public bool HasItems { get { return Items != null && Items.Count > 0; } }
public DateTime EditDate { get; set; }
private ObservableCollection<Item> GenerateMockItems()
{
var collection = new ObservableCollection<Item>();
for (int i = 0; i < 10; i++)
{
collection.Add(new Item() { Name="sdfsdfs" , Channel=i });
}
return collection;
}
private DateTime GenerateRandomFutureDate()
{
return DateTime.Now.AddSeconds(new Random().Next(0,50000));
}
}

Related

UWP/C# ItemsControl Multiple Boxes?

I have had a lot of help so far with creating the correct formatting for an ItemsControl panel and appreciate this communities help so far with helping me troubleshoot coding issues.
Im currently at a rather small hurdle where im trying to figure out how to create multiple boxes within the same ItemsControl. Currently the overall view looks like this:
Im a little stumped and would just like a little guidance really as to where to put the other XAML lines.
I need it to look like this:
Here is my code currently (its all nested within a Frame):
<ItemsControl ItemsSource="{StaticResource userDataCollection}" Margin="40,40,40,725" Width="Auto" Height="310">
<!-- Changing Orientation of VirtualizingStackPanel -->
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<!-- Change header for ItemsControl -->
<ItemsControl.Template>
<ControlTemplate>
<Border Background="{StaticResource CustomAcrylicDarkBackground}">
<StackPanel>
<TextBlock Text="Accounts At A Glance" FontSize="28" Foreground="#b880fc" Padding="12"/>
<ItemsPresenter/>
</StackPanel>
</Border>
</ControlTemplate>
</ItemsControl.Template>
<!-- Template for each card-->
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid Width="240" Height="240" Background="Gray" Margin="30,0,0,0" VerticalAlignment="Center" Padding="4">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBlock Grid.Row="0" Text="{Binding Name}" HorizontalAlignment="Center" TextAlignment="Center" Width="220" FontSize="24"/>
<TextBlock Grid.Row="1" Text="{Binding PayDate}" HorizontalAlignment="Center" TextAlignment="Center" Width="220" FontSize="14" />
<TextBlock Grid.Row="2" Text="{Binding NumberOfItems}" HorizontalAlignment="Center" TextAlignment="Center" Width="220" FontSize="14"/>
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
I really apologise for this, im trying to learn as much as i can as i go. Im mainly stuggling with the XAML formatting and incorperating learning material into my project :/ Any help would be amazing
I have an alternative approach for your problem. This uses "semi" MVVM approach (browse through the net and study this pattern).
MainPageViewModel.cs
public class MainPageViewModel : INotifyPropertyChanged
{
private ObservableCollection<User> _userCollection;
public event PropertyChangedEventHandler PropertyChanged;
public ObservableCollection<User> UserCollection
{
get => _userCollection;
set
{
_userCollection = value;
NotifyProperyChanged();
}
}
private void NotifyProperyChanged([CallerMemberName]string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public void LoadData()
{
UserCollection = new ObservableCollection<User>
{
new User
{
Name = "John Doe",
PayDate = DateTime.Now,
NumberOfItems = 1
},
new User
{
Name = "John Doe 2",
PayDate = DateTime.Now,
NumberOfItems = 1
},
new User
{
Name = "John Doe 3",
PayDate = DateTime.Now,
NumberOfItems = 1
},
};
}
}
The view (got rid of some styling temporarily):
<Page
x:Class="App1.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:vm="using:App1.ViewModels"
mc:Ignorable="d"
Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
Loaded="MainPage_OnLoaded">
<Page.DataContext>
<vm:MainPageViewModel/>
</Page.DataContext>
<Grid>
<ScrollViewer>
<ItemsControl ItemsSource="{Binding UserCollection, Mode=TwoWay}" Margin="15" Width="Auto" Height="310">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<!-- Template for each card-->
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid Width="200" Height="100" Background="Gray" Margin="15,0,0,0" VerticalAlignment="Center" Padding="4">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBlock Grid.Row="0" Text="{Binding Name}" HorizontalAlignment="Center" TextAlignment="Center" Width="220" FontSize="24"/>
<TextBlock Grid.Row="1" Text="{Binding PayDate}" HorizontalAlignment="Center" TextAlignment="Center" Width="220" FontSize="14" />
<TextBlock Grid.Row="2" Text="{Binding NumberOfItems}" HorizontalAlignment="Center" TextAlignment="Center" Width="220" FontSize="14"/>
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</ScrollViewer>
</Grid>
</Page>
View's code-behind:
namespace App1
{
public sealed partial class MainPage
{
public MainPage()
{
this.InitializeComponent();
}
public MainPageViewModel VM => (MainPageViewModel) DataContext;
private void MainPage_OnLoaded(object sender, RoutedEventArgs e)
{
VM.LoadData();
}
}
}
Output:
Next steps:
Apply your styling. Study how to limit grid columns.
Improve the code
further, in MVVM you shouldn't really have implementations on the
code-behind, so study for ICommand, Microsoft.Xaml.Interactivity
Hope this helps.
It perfect now.
Im an idiot.
I essentially needed to seperate the information presented within the UserData.cs Class. I didnt understand how the information was being read but understand it now. The XAML has been left untouched as it works currently for what i need. It will be update to follow the MVVM format as mentioned by Mac. Here is the UserData.CS class located inside a data folder:
using System.Collections.ObjectModel;
namespace BudgetSheet.Data
{
public class UserData
{
public string Name { get; set; }
public string PayDate { get; set; }
public string NumberOfItems { get; set; }
}
class UserDataCollection : ObservableCollection<UserData>
{
public UserDataCollection()
{
// Placeholder, needs to be replaced with CSV or Database information
this.Add(new UserData()
{
Name = "Selected Username",
PayDate = "Friday",
NumberOfItems = "ItemAmount Placeholder"
});
// Placeholder for user 2
this.Add(new UserData()
{
Name = "Selected Username 2",
PayDate = "Friday 2",
NumberOfItems = "ItemAmount Placeholder 2"
});
// Placeholder for user 3
this.Add(new UserData()
{
Name = "Selected Username 3",
PayDate = "Friday 3",
NumberOfItems = "ItemAmount Placeholder 3"
});
}
}
}
Here is what it was before hand and why there were issues with information display:
using System.Collections.ObjectModel;
namespace BudgetSheet.Data
{
public class UserData
{
public string Name { get; set; }
public string PayDate { get; set; }
public string NumberOfItems { get; set; }
}
class UserDataCollection : ObservableCollection<UserData>
{
public UserDataCollection()
{
// Placeholder, needs to be replaced with CSV or Database information
this.Add(new UserData()
{
Name = "Selected Username",
});
// Placeholder for user selected PayDate
this.Add(new UserData()
{
PayDate = "Friday",
});
// Placeholder for user selected PayDate
this.Add(new UserData()
{
NumberOfItems = "ItemAmount Placeholder"
});
}
}
}
This solution does not provide much flexibility currently but it works for the formatting. Marking as resolved to close the ticket

How to bind to IsExpanded property - to persist the TreeView's expanded state?

In the ViewModel I have defined a bool ShouldExpand property, bound to it in from the TreeView's itemcontainerstyle - it does not work.
This answer (WinRT XAML Toolkit TreeView Save state) would've answered my question, but it does not work...
Is there a WORKING code snippet?
public class AgendaItemTreeView : ViewModelBase
{
private string _title;
private Visibility _documentGridVisibility = Visibility.Collapsed;
private bool _shouldExpand;
// Binding property - to display in a TreeView
public string Title
{
get { return _title; }
set { Set(ref _title, value); }
}
// To expand/collapse documents GridView
public Visibility DocumentGridVisibility
{
get { return _documentGridVisibility; }
set { Set(ref _documentGridVisibility, value); }
}
// Property to expand/collapse a node in a TreeView - does not work!
public bool ShouldExpand
{
get { return _shouldExpand; }
set { Set(ref _shouldExpand, value); }
}
// Nested agenda items
public ObservableCollection<AgendaItemTreeView> AgendaItems { get; set; } = new ObservableCollection<AgendaItemTreeView>();
// Documents of current agenda item
public ObservableCollection<DocumentViewModel> Documents { get; set; } = new ObservableCollection<DocumentViewModel>();
public DocumentViewModel SelectedItem { get; set; }
public AgendaItemTreeView(AgendaItem agendaItem, string selectedTitle = "")
{
// Constructor populating the nested AgendaItem & Documents
}
}
XAML:
<UserControl
<UserControl.Resources>
<!--<Style x:Key="TreeViewItemContainerStyle" TargetType="controls:TreeViewItem">
<Setter Property="IsExpanded" Value="{Binding ShouldExpand, Mode=TwoWay}"/>
</Style>-->
<!-- Folder type Node, that can contain other 'folders' and 'files' -->
<DataTemplate x:Key="TreeViewItemTemplate" x:DataType="vm:AgendaItemTreeView">
<data:DataTemplateExtensions.Hierarchy>
<data:HierarchicalDataTemplate ItemsSource="{Binding AgendaItems}" />
<!-- When the next line used together with the Style TreeViewItemContainerStyle - the TreeView still does not expand the top level tree. The app C
<!--<data:HierarchicalDataTemplate ItemsSource="{Binding AgendaItems}" ItemContainerStyle="{StaticResource TreeViewItemContainerStyle}"/>-->
</data:DataTemplateExtensions.Hierarchy>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<ToggleButton x:Name="titleToggleBtn" Tapped="{x:Bind ExpandDocumentsCommand}">
<StackPanel Orientation="Horizontal">
<SymbolIcon Symbol="{x:Bind DocumentsIcon}" Margin="5,0"/>
<TextBlock Text="{Binding Title}"/>
</StackPanel>
</ToggleButton>
<GridView Grid.Row="1" x:Name="DocumentsGrid" ItemsSource="{Binding Documents}" ItemTemplate="{StaticResource ZoomedInTemplate}" Visibility="{Binding DocumentGridVisibility}" SelectedItem="{Binding SelectedItem}"/>
</Grid>
</DataTemplate>
<!-- Nested 'file' type Node data template -->
<DataTemplate x:Key="ZoomedInTemplate" x:DataType="vm:DocumentViewModel">
<Border BorderBrush="Black" Padding="5" BorderThickness="1" Width="100">
<Grid Tapped="{x:Bind TappedCommand}">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition />
</Grid.RowDefinitions>
<Image Source="{Binding Thumbnail}" Width="60" Height="80" />
<TextBlock Grid.Row="1" Text="{x:Bind Title, Mode=OneWay}" VerticalAlignment="Center" Tapped="{x:Bind TappedCommand}"/>
</Grid>
</Border>
</DataTemplate>
</UserControl.Resources>
<Grid d:DataContext="{d:DesignData /SampleData/AgendaItemTreeViewSampleData.xaml}">
<controls:TreeView x:Name="myTreeView"
ItemsSource="{x:Bind TreeItems}"
ItemTemplate="{StaticResource TreeViewItemTemplate}" />
</Grid>
</UserControl>

How to Bind IsSelected Property in DataTemplate of ListViewItem

Well, I want to make the ListViewItem in UWP ,that'll be changing his view on selecting. So I need to change the Visibility property of some elements of ListViewItem on selecting.
I found some way to do this with making custom Style of ListViewItem and Binding IsSelected property like this:
<Style x:Key="VehicleListViewItemStyle" TargetType="ListViewItem" >
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ListViewItem">
<Grid Background="Gray" Margin="1">
<Border Margin="2" Padding="10" Background="Gray" >
<StackPanel>
<ContentPresenter x:Name="Presenter1" />
<StackPanel Orientation="Horizontal" Background="Transparent" Margin="-10,0,-9,-9" VerticalAlignment="Center" x:Name="infoPanel"
Visibility="{Binding IsSelected, RelativeSource={RelativeSource Mode=TemplatedParent}, Converter={StaticResource BooleanToVisibilityConverter}}">
<TextBlock Text="{Binding DeviceID}/> </StackPanel>
</StackPanel>
</Border>
<Border BorderThickness="1" BorderBrush="Orange" Visibility="{Binding IsSelected, RelativeSource={RelativeSource Mode=TemplatedParent}, Converter={StaticResource BooleanToVisibilityConverter}}"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Its working good, but with this way I cant bind the DeviceID text.
Another one way is creating DataTemplate like this:
<DataTemplate x:Key="monitoringListViewItem" x:Name="item">
<Grid Background="Gray" Margin="1" Width="300" >
<StackPanel>
<ContentPresenter x:Name="Presenter"/>
<StackPanel Orientation="Horizontal">
<Image Source="/Assets/14th_crane_stop.png" Height="50" Width="50" Stretch="Uniform"/>
<StackPanel Orientation="Vertical" Margin="25,0,0,0 "
Visibility="{Binding IsSelected, RelativeSource={RelativeSource Mode=TemplatedParent}, Converter={StaticResource BooleanToVisibilityConverter}}"
>
<TextBlock Text="{Binding DeviceID}" Style="{StaticResource VehicleTextStyle}"/>
<TextBlock Text="{Binding Mark}" Style="{StaticResource VehicleTextStyle}"/>
</StackPanel>
</StackPanel>
</StackPanel >
</Grid>
</DataTemplate>
Now I can bind the text correctly, but cant bind the IsSelected property. I've tried to do this with different Modes, but it still doesn't work because I cant use the TemplatedParent key inside the DataTemplate.
So I need some answers:
-can I bind the text in first way and how can I do that?
-how can I bind the IsSelected property in the second way?
I don't recommend changing the ListViewItem template since you lose all the bells and whistles it provides (selection appearance, ability to be checked, etc).
Using Mode=TemplatedParent in the second snippet won't work because the templated parent from that context is a ListViewItemPresenter, not the ListViewItem (which is the presenter's parent).
It looks like what you're trying to do is to show additional information in the list item when it is selected.
Single selection
C# classes
public class NotifyPropertyChangedBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged([CallerMemberName] string propertyName = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
protected bool SetProperty<T>(ref T property, T value, [CallerMemberName] string propertyName = "")
{
if (EqualityComparer<T>.Default.Equals(property, value))
{
return false;
}
property = value;
OnPropertyChanged(propertyName);
return true;
}
}
public class Item : NotifyPropertyChangedBase
{
private string text;
public string Text
{
get { return text; }
set { SetProperty(ref text, value); }
}
private bool isSelected;
public bool IsSelected
{
get { return isSelected; }
set { SetProperty(ref isSelected, value); }
}
}
public class MainPageViewModel : NotifyPropertyChangedBase
{
public List<Item> Items { get; set; }
private Item selectedItem;
public Item SelectedItem
{
get { return selectedItem; }
set
{
if (selectedItem != value)
{
if (selectedItem != null)
{
selectedItem.IsSelected = false;
}
SetProperty(ref selectedItem, value);
if (selectedItem != null)
{
selectedItem.IsSelected = true;
}
}
}
}
public MainPageViewModel()
{
Items = new List<Item>()
{
new Item() { Text = "Apple" },
new Item() { Text = "Banana" },
};
}
}
MainPage.xaml
<ListView ItemsSource="{Binding Items}" SelectedItem="{Binding SelectedItem, Mode=TwoWay}">
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
</Style>
</ListView.ItemContainerStyle>
<ListView.ItemTemplate>
<DataTemplate x:DataType="local:Item">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding Text}"/>
<!-- x:Bind doesn't require visibility converter if min SDK is targeting Anniversary update -->
<TextBlock Text="I'm selected!" Grid.Column="1" Visibility="{x:Bind IsSelected, Mode=OneWay}"/>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
MainPage.xaml.cs
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
DataContext = new MainPageViewModel();
}
}
Multiple selection
Same as single selection but with the following changes:
MainPageViewModel
public class MainPageViewModel : NotifyPropertyChangedBase
{
public List<Item> Items { get; set; }
public MainPageViewModel()
{
Items = new List<Item>()
{
new Item() { Text = "Apple" },
new Item() { Text = "Banana" },
};
}
public void SelectionChanged(object sender, SelectionChangedEventArgs e)
{
foreach (Item item in e.RemovedItems)
{
item.IsSelected = false;
}
foreach (Item item in e.AddedItems)
{
item.IsSelected = true;
}
}
}
MainPage.xaml
<ListView ItemsSource="{Binding Items}" SelectionChanged="{x:Bind ViewModel.SelectionChanged}" SelectionMode="Extended">
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
</Style>
</ListView.ItemContainerStyle>
<ListView.ItemTemplate>
<DataTemplate x:DataType="local:Item">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding Text}"/>
<TextBlock Text="I'm selected!" Grid.Column="1" Visibility="{x:Bind IsSelected, Mode=OneWay}"/>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
MainPage.xaml.cs
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
DataContext = new MainPageViewModel();
}
public MainPageViewModel ViewModel => (MainPageViewModel)DataContext;
}
To answer the actual question in the topic: Yes you can bind ListViewItem.IsSelected quite easily. Make sure your DataTemplate content is wrapped in a ListViewItem.
<ListView.ItemTemplate>
<DataTemplate x:DataType="local:MyItemViewModel">
<ListViewItem IsSelected="{Binding IsSelected, Mode=TwoWay}">
<Grid>
// template content
</Grid>
</ListViewItem>
</DataTemplate>
</ListView.ItemTemplate>
Note that there are numerous Q&As here for WPF saying this does not work. It does work with UWP (at least as of SDK 10.0.19041). The WPF answers suggest binding it in the ItemsPanelTemplate or in a ResourceDictionary. For some reason this does not work in UWP.
I did the following and it worked fine
<ListView.ItemTemplate>
<DataTemplate x:DataType="local:PersonalProfile">
<ListViewItem x:Name="root">
<Grid >
<!-- .... -->
<CheckBox IsChecked="{Binding ElementName=root, Path=IsSelected, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
</Grid>
</ListViewItem>
</DataTemplate>
</ListView.ItemTemplate>

TwoWay Data Binding with MVVM Light on Windows Phone 8.1

I'm trying to create a custom Button with ListPickerFlyout using MVVM. The result that i wanna reach is something like that:
custom Button with ListPickerFlyout
My problem is how to bind the SelectedItem from ListPickerFlyout to the content TextBlock.
I'm using MVVM Light Windows Phone 8.1 (Store Appp).
My Xaml code:
<Button Background="White"
HorizontalAlignment="Stretch"
HorizontalContentAlignment="Stretch">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="40" />
</Grid.ColumnDefinitions>
<!-- Content TextBlock -->
<TextBlock Text="{Binding MyVM.SelectedItem, Mode=TwoWay}"
Style="{StaticResource DefaultTextBlock}"
FontSize="22"
HorizontalAlignment="Left"
VerticalAlignment="Center"
Margin="10, 0, 0, 0"/>
<Image Height="20" Grid.Column="1"
VerticalAlignment="Center" HorizontalAlignment="Center"
Source="../Assets/icons/arrow_down.png"/>
</Grid>
<Button.Flyout>
<ListPickerFlyout PickerFlyoutBase.Title="$Items$"
ItemsSource="{Binding MyVM.listItems}"
SelectedItem="{Binding MyVM.SelectedItem, Mode=TwoWay}" >
<ListPickerFlyout.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding}"
Style="{StaticResource DefaultTextBlock}"
FontSize="22"/>
</StackPanel>
</DataTemplate>
</ListPickerFlyout.ItemTemplate>
</ListPickerFlyout>
</Button.Flyout>
And in MyVM i have
public string SelectedItem { get; set; }
Edit:
Solved the problem, i forgot to add RaisePropertyChanged("SelectedItem");.
So, in my MVVM class:
private string _selectedItem;
public string SelectedItem
{
get { return _selectedItem; }
set
{
if (_selectedItem != value)
{
_selectedItem = value;
RaisePropertyChanged("SelectedItem");
}
}
}
Just need to add the RaisePropertyChanged("SelectedItem"); in MVVM class.
The complete code:
private string _selectedItem;
public string SelectedItem
{
get { return _selectedItem; }
set
{
if (_selectedItem != value)
{
_selectedItem = value;
RaisePropertyChanged("SelectedItem");
}
}
}

Update XAML Binding after a property changes

I am using MVVM light on a Windows 8.1 Store app. I have a view model that has several properties on it that have no setters (their value is derived from a different property). Here is part of my ViewModel:
public float TotalAmount
{
get
{
if (!LineItems.Any())
return 0.0f;
return SubTotal + TotalFees - TotalDiscounts;
}
}
public float SubTotal
{
get
{
return !LineItems.Any() ? 0.0f : LineItems.Select(i => i.Price.Amount).Sum();
}
}
public float TotalFees
{
get
{
return !Fees.Any() ? 0.0f : Fees.Select(f => f.Amount).Sum();
}
}
public float TotalDiscounts
{
get
{
return !Discounts.Any() ? 0.0f : Discounts.Select(d => d.Amount).Sum();
}
}
public ObservableCollection<Discount> Discounts { get; set; }
public ObservableCollection<Fee> Fees { get; set; }
public Customer Customer { get; set; }
public ObservableCollection<OrderLineItem> LineItems { get; set; }
In the XAML, I bind to each of these properties, and want to update them when an Item is added to LineItems.
Here is the relevant part of the XAML:
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="3*" />
<ColumnDefinition Width="1*" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<TextBlock Text="SubTotal:" Style="{StaticResource OrderDetailsLabel}" />
<TextBlock Grid.Column="1" Style="{StaticResource OrderDetailsValue}"
Text="{Binding SubTotal, Converter={StaticResource MoneyConverter}, Mode=TwoWay}" />
<TextBlock Grid.Row="1" Text="Fees:" Style="{StaticResource OrderDetailsLabel}" />
<TextBlock Grid.Row="1" Style="{StaticResource OrderDetailsValue}" Grid.Column="1"
Text="{Binding TotalFees, Converter={StaticResource MoneyConverter}, Mode=TwoWay}" />
<TextBlock Grid.Row="2" Text="Discounts:" Style="{StaticResource OrderDetailsLabel}" />
<TextBlock Grid.Row="2" Style="{StaticResource OrderDetailsValue}" Grid.Column="1"
Text="{Binding TotalDiscounts, Converter={StaticResource MoneyConverter}, Mode=TwoWay}" />
<TextBlock Grid.Row="3" Text="Order Total:" Style="{StaticResource OrderDetailsLabel}" />
<TextBlock Grid.Row="3" Style="{StaticResource OrderDetailsValue}" Grid.Column="1"
Text="{Binding TotalAmount, Converter={StaticResource MoneyConverter}, Mode=TwoWay}" />
</Grid>
My Binding to the LineItems is working as expected, but the fields that are populated by doing math on the line items are not.
Line Item Binding functioning as expected:
<ListView ItemsSource="{Binding LineItems, Mode=TwoWay}"
SelectionMode="Single"
HorizontalAlignment="Stretch">
<ListView.ItemContainerStyle>
....
How can I get SubTotal, Total, etc. to update when LineItems changes?
Pretty simple:
Register the ObservableCollection<T>.CollectionChanged event for each of those collection. Since your desired properties are based on some calculation of the collection.
On event fire Raise the OnPropertyChanged on those properties.
Example how to raise the OnPropertyChanged/inotifypropertychanged
MSDN: inotifypropertychanged Example
Something like this in your constructor:
LineItems.CollectionChanged += (s, e) =>
{
RaisePropertyChanged("SubTotal");
RaisePropertyChanged("TotalFees");
RaisePropertyChanged("TotalDiscounts");
}
assuming your ViewModel implements INotifyPropertyChanged, and has a 'RaisePropertyChanged' method that raises the PropertyChanged event (e.g. You're using MVVM-Light's ViewModelBase as your baseclass).
I ended up solving this by raising the OnPropertyChanged event on in the handler for my AddLineItems message:
public NewOrderViewModel()
{
//Subscribe to messages
MessengerInstance.Register<OrderItemAdded>(this, o => AddOrderItem(o.LineItem));
MessengerInstance.Register<SelectedCustomer>(this, c => Customer = c.Customer);
Discounts = new ObservableCollection<Discount>();
Fees = new ObservableCollection<Fee>();
LineItems = new ObservableCollection<OrderLineItem>();
}
private void AddOrderItem(OrderLineItem lineItem)
{
//add Line Item to collection
LineItems.Add(lineItem);
//Raise events for properties derived from collection
RaisePropertyChanged("TotalAmount");
RaisePropertyChanged("SubTotal");
}