Develop Reference

WPF C# get Object properties without adding extra variables into the viewmodel

I'm curently trying to implemnt a Combobox binding to a list and some labels showing the details of a selected object. The binding to the Combobox works without any problems but I don't want to add extra variables into my ViewModel just to display the name and speed of my car objects.
Is there any way to Map the object variables of the selected combobox item on to the labels without adding additional variables into my ViewModel?
That's the code I'm currently working with
MainWondow.xaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace StackOF
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
private ViewModel viewModel;
public MainWindow()
{
viewModel = new ViewModel();
DataContext = viewModel;
InitializeComponent();
}
}
}
ViewModel.cs
using _02_WPFCarInfo.AutoKlassen;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;
namespace StackOF
{
public class ViewModel : INotifyPropertyChanged
{
private ObservableCollection<AutoModel> _autoModels;
private AutoModel selectedModel;
public ObservableCollection<AutoModel> AutoModels
{
get { return _autoModels; }
set
{
_autoModels = value;
OnPropertyChanged();
}
}
public AutoModel SelectedModel
{
get { return selectedModel; }
set
{
selectedModel = value;
OnPropertyChanged();
}
}
public ViewModel()
{
_autoModels = generateCars();
}
private ObservableCollection<AutoModel> generateCars()
{
AutoModel model1 = new AutoModel();
AutoModel model2 = new AutoModel();
AutoModel model3 = new AutoModel();
model1.name = "Mercedes C12 Pro";
model1.speed = "125 km\\h";
model2.name = "Audi A12";
model2.speed = "236 km\\h";
model3.name = "Audi S20 Pro";
model3.speed = "300 km\\h";
ObservableCollection<AutoModel> cars = new ObservableCollection<AutoModel>();
cars.Add(model1);
cars.Add(model2);
cars.Add(model3);
return cars;
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
}
MainWindow.xaml
<Window x:Class="StackOF.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:StackOF"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Grid>
<ComboBox SelectedItem="{Binding SelectedModel}" DisplayMemberPath="name" ItemsSource="{Binding AutoModels}" HorizontalAlignment="Center" Margin="0,164,0,0" VerticalAlignment="Top" Width="212"/>
<Label Content="Name:" HorizontalAlignment="Left" Margin="294,231,0,0" VerticalAlignment="Top"/>
<Label Content="Speed:" HorizontalAlignment="Left" Margin="294,262,0,0" VerticalAlignment="Top"/>
<TextBlock HorizontalAlignment="Center" Margin="0,241,0,0" TextWrapping="Wrap" Text="---" VerticalAlignment="Top" RenderTransformOrigin="0.287,-1.303"/>
<TextBlock HorizontalAlignment="Center" Margin="0,267,0,0" TextWrapping="Wrap" Text="---" VerticalAlignment="Top" RenderTransformOrigin="0.287,-1.303"/>
</Grid>
</Window>
AutoModel.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace _02_WPFCarInfo.AutoKlassen
{
public class AutoModel
{
public String name { get; set; }
public String speed { get; set; }
public AutoModel()
{
this.speed = String.Empty;
this.name = String.Empty;
}
public AutoModel(String name, String speed)
{
this.speed = speed;
this.name = name;
}
}
}
I thought about something like :
<TextBlock HorizontalAlignment="Center" Margin="0,241,0,0" TextWrapping="Wrap" Text="{Binding SelectedModel.name}" VerticalAlignment="Top" RenderTransformOrigin="0.287,-1.303"/>
<TextBlock HorizontalAlignment="Center" Margin="0,267,0,0" TextWrapping="Wrap" Text="{Binding SelectedModel.speed}" VerticalAlignment="Top" RenderTransformOrigin="0.287,-1.303"/>
But obviously it is not possible to select the variables of "SelectedModel" that way.

Ok nvm it DOES work. It only does not work if you have a textblock with opening and closing tag with text inbetween
This works:
<TextBlock HorizontalAlignment="Center" Margin="0,241,0,0" TextWrapping="Wrap" Text="{Binding SelectedModel.name}" VerticalAlignment="Top" RenderTransformOrigin="0.287,-1.303"/>
but this doesn't
<TextBlock HorizontalAlignment="Center" Margin="0,241,0,0" TextWrapping="Wrap" Text="{Binding SelectedModel.name}" VerticalAlignment="Top" RenderTransformOrigin="0.287,-1.303">---</TextBlock>

Get rid of Visual Studio Namespace error message

this is unfortunately a very beginner question:
I am doing the very simple WPF tutorials and I am stuck on a namespace problem.
I want to do a simple hierarchical treeview binding on a custom object according to the tutorial. I put the object into a custom namespace "MyNameSpace" and declared this in XAML ( xmlns:MyTree="clr-namespace:MyNameSpace"). I believe I don't need to specify the assembly as I am just in my project without any further reference (new and clean project).
The problem I have now, is that the compiler gives me an error at
<HierarchicalDataTemplate DataType="{x:Type MyTree:MenuItemNew}"
with the message
The name "MenuItemNew" does not exist in the namespace "clr-namespace:MyNameSpace"
But it does exist! AND it even compiles and starts the program correctly. However, I cannot see the layout anymore because of "Invalid Markup".
So how can I tell XAML to accept my namespace? Or what would be a best way to solve this?
Here is the XAML:
<Window x:Class="TreeViewTestC.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:MyTree="clr-namespace:MyNameSpace"
Title="MainWindow" Height="350" Width="525">
<Grid Margin="10">
<TreeView Name="trvMenu">
<TreeView.ItemTemplate>
<HierarchicalDataTemplate DataType="{x:Type MyTree:MenuItemNew}" ItemsSource="{Binding Items}">
<TextBlock Text="{Binding Title}" />
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
</Grid>
</Window>
and here is my MainWindow Code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.IO;
using System.Collections.ObjectModel;
using MyNameSpace;
namespace TreeViewTestC
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
MenuItemNew root = new MenuItemNew() { Title = "Menu1" };
MenuItemNew childItem1 = new MenuItemNew() { Title = "Child item #1" };
childItem1.Items.Add(new MenuItemNew() { Title = "Child item #1.1" });
childItem1.Items.Add(new MenuItemNew() { Title = "Child item #1.2" });
root.Items.Add(childItem1);
root.Items.Add(new MenuItemNew() { Title = "Child item #2" });
trvMenu.Items.Add(root);
}
}
}
namespace MyNameSpace
{
public class MenuItemNew
{
public MenuItemNew()
{
this.Items = new ObservableCollection<MenuItemNew>();
}
public string Title { get; set; }
public ObservableCollection<MenuItemNew> Items { get; set; }
}
}

It seems to me that your main application namespace is TreeViewTestC and not MyNameSpace. Therefore, you may well need to tell the compiler that your MyNameSpace is actually in the TreeViewTestC assembly, despite you only having a single project. Try using this instead:
xmlns:MyTree="clr-namespace:MyNameSpace;assembly=TreeViewTestC"

Ok, I found the solution. The project was on a network drive. Moving it to a local folder solves the issues...
Man, what a mess. This has cost me so much time and I need the network drive..
More info:
The name "XYZ" does not exist in the namespace "clr-namespace:ABC"
Thanks a lot for your help

Editable combobox overwrites my context menu - Fails

I have been trying to use the code in the reply to Question
"Editable combobox overwrites my context menu" asked on asked Aug 30 '12 at 14:24
But it always errors with a nullreferenceerror on
(VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(combobox, 0), 2) as TextBox).ContextMenu = combobox.ContextMenu;
In order to minimize any environment problems I have added the code as a new project
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<ComboBox IsEditable="True" ContextMenuService.ShowOnDisabled="True"
Name="combobox" Loaded="combobox_Loaded">
<ComboBox.ContextMenu>
<ContextMenu>
<MenuItem Header="test"></MenuItem>
</ContextMenu>
</ComboBox.ContextMenu>
<ComboBoxItem Content="Item1"></ComboBoxItem>
<ComboBoxItem Content="Item2"></ComboBoxItem>
</ComboBox>
</Grid>
</Window>
code
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace WpfApplication1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void combobox_Loaded(object sender, RoutedEventArgs e)
{
(VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(combobox, 0), 2) as TextBox).ContextMenu = combobox.ContextMenu;
}
}
}

This is working:
private void combobox_Loaded(object sender, RoutedEventArgs e)
{
(VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(combobox, 0), 2), 0) as TextBox).ContextMenu = combobox.ContextMenu;
}
You have to go another level.
Because the TextBox is inside a border.
You can use Snoop application to inspect the xaml tree.

Using an object in code, which is instantiated in xaml

I am trying to experiment making simple GUI application.
In it I have made a simple class called consle. I am using a button click to trigger an event Button_Click_1. This should in turn call the function wrStr which changes the value of variable change internally. This changed value should reflect in the GUI because the variable change is also bound in the XAML code.
The problem is, I do not know how to access the consle type object instantiated in XAML code. If I get the name of the object instantiated in XAML I could just say <NameOfObject>.wrStr() inside the Button_Click_1 function.
The XAML code is given below:
<Window x:Class="TryBinding.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:TryBinding"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Button Content="Set44" HorizontalAlignment="Left" Margin="244,37,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click_1"/>
<TextBlock HorizontalAlignment="Left" Margin="339,76,0,0" TextWrapping="Wrap" Text="{Binding Source=consle, Path=change, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Top"/>
</Grid>
The cs code is as follows:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace TryBinding
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void Button_Click_1(object sender, RoutedEventArgs e)
{
}
}
public class consle
{
public string mainstr {get; set;}
public int change { get; set; }
public consle()
{
}
public void wrStr()
{
change = 44;
}
}
}

How do I bind to a List<T> using DataContext?

I'm self-learning C#, OOP, and WPF so the potential for stuff ups is staggering.
So given that, can someone please explain why after clicking the button in my tiny test example the Name property appears in the TextBox but the ListBox shows nothing?
XAML:
<Window x:Class="BindingTest.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="BindingTest" Height="250" Width="300">
<Grid Name="mainGrid">
<Grid.RowDefinitions>
<RowDefinition Height="50" />
<RowDefinition Height="50" />
<RowDefinition Height="100" />
</Grid.RowDefinitions>
<Button
Grid.Row="0"
Name="MakeIntListButton"
Click="MakeIntListButton_Click">Make and Display Integer List</Button>
<TextBox Grid.Row="1" Text ="{Binding Path=Name}"
/>
<ListBox
Grid.Row="2"
ItemsSource="{Binding Path=MyIntegers}"
/>
</Grid>
C#:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace BindingTest
{
/// <summary>
/// Interaction logic for Window1.xaml
/// </summary>
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
}
private void MakeIntListButton_Click(object sender, RoutedEventArgs e)
{
AClass InstanceOfAClass = new AClass();
InstanceOfAClass.MyIntegers.Add(6);
InstanceOfAClass.MyIntegers.Add(7);
InstanceOfAClass.MyIntegers.Add(42);
InstanceOfAClass.Name = "Fred";
mainGrid.DataContext =InstanceOfAClass ;
}
}
public class AClass
{
public string Name {get;set;}
public List<int> MyIntegers = new List<int>();
}
}

Part of me wonders whether it's something to do with the fact that "MyIntegers" is a public field rather than a property. Can you refactor you class to look like this and try it?
public class AClass
{
private List<int> _ints = new List<int>();
public string Name { get; set; }
public List<int> MyIntegers
{
get { return _ints; }
}
}

I ran your sample and when I clicked on the button the TextBox was populated with the Name as expected.
The only problem I encountered was that the ListView was not getting populated with the list of integers. That's to do with the fact that XAML is not very comfortable with generics if you modify it to bind to an array instead it works. WPF supports consumption of XAML fine, it's using generics within XAML that's not supported. As Matt Hamilton points out in his answer MyIntegers just needs to be made a propety by adding a get acessor.
Add C# Property:
public int[] MyInts { get { return MyIntegers.ToArray(); } }
XAML:
<ListBox Grid.Row="2" ItemsSource="{Binding Path=MyInts}" />

Look into using the System.Collections.ObjectModel.ObservableCollection for list binding instead of a plain List.