NullReferenceException loading RenderWindowControl for vtk in WPF - c#

I am trying to load a RenderWindowControl from vtk libraries on my WPF proyect using ActiViz.NET and Visual Studio 2013. The library works fine since I did a new project just to practice on itbut when I tried to integrate it into my work, I got a null RenderWindowControl this time. This is my code:
MainWindow.xaml:
<Window x:Class="myProject.Views.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:VtkTab="clr-namespace:myProject.Views.UITabs.VtkTab"
x:Name="Mainwindow"
MinHeight="600"
MinWidth="800"
Title="{Binding Title}"
Height="720"
Width="1280"
Icon="{StaticResource ApplicationIcon}"
Loaded="OnLoaded"
DataContext="{Binding Main, Source={StaticResource ViewModelLocator}}"
Style="{StaticResource WindowStyle}"
mc:Ignorable="d">
<DockPanel>
<TabControl>
....
....
<VtkTab:VtkTabView />
....
....
</TabControl>
</DockPanel>
</Window>
VtkTabView.xaml:
<UserControl x:Class="myProject.Views.UITabs.VtkTab.VtkTabView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vtk="clr-namespace:Kitware.VTK;assembly=Kitware.VTK"
Loaded="WindowLoaded"
Height="480" Width="640">
<WindowsFormsHost Name="Wfh">
<vtk:RenderWindowControl x:Name="RenderControl" />
</WindowsFormsHost>
</UserControl>
VtkTabView.xaml.cs:
public partial class UITabView
{
protected static Random _random = new Random();
vtkActor actor = vtkActor.New();
public VtkTabView()
{
InitializeComponent();
var sphere = vtkSphereSource.New();
sphere.SetThetaResolution(8);
sphere.SetPhiResolution(16);
var shrink = vtkShrinkPolyData.New();
shrink.SetInputConnection(sphere.GetOutputPort());
shrink.SetShrinkFactor(0.9);
var move = vtkTransform.New();
move.Translate(_random.NextDouble(), _random.NextDouble(), _random.NextDouble());
var moveFilter = vtkTransformPolyDataFilter.New();
moveFilter.SetTransform(move);
moveFilter.SetInputConnection(shrink.GetOutputPort());
var mapper = vtkPolyDataMapper.New();
mapper.SetInputConnection(moveFilter.GetOutputPort());
// The actor links the data pipeline to the rendering subsystem
actor.SetMapper(mapper);
actor.GetProperty().SetColor(1, 0, 0);
}
private void WindowLoaded(object sender, RoutedEventArgs e)
{
var renderer = RenderControl.RenderWindow.GetRenderers().GetFirstRenderer();
renderer.AddActor(actor);
}
}
RenderControl.RenderWindow is null on WindowLoaded (VtkTabView.xaml.cs) and I do not know why. Might it be because I load UITabView from a second xamp and I lose the content of RenderControl?, it is the only difference I see compare to the example I did.

Access the RenderWindow on Load event of the RenderWindowControl.
e.g.
public VtkTabView()
{
InitializeComponent();
// initialize your sphrere and actor
RenderControl.Load += MyRenderWindowControlOnLoad;
}
private void MyRenderWindowControlOnLoad(object sender_in, EventArgs eventArgs_in){
//access the RenderWindow here
}

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Can't Access Button from drag n drop UI programatically

I created a new WPF app in Visual Studio and I placed a button using the drag and drop editor but I can't access the button in my .cs file using
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but I get an error
System.NullReferenceException: 'Object reference not set to an instance of an object.'
MainButton was null while running the application.
The drag and drop editor generated this xaml file
<Window x:Class="WpfApp1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
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Here's the .cs file
using System.Windows;
using System.Windows.Media;
namespace WpfApp1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
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}
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else
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MainButton.Content = "Set output to blue";
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}
}
I can access other things in the UI just fine like radio buttons and text blocks but not the button. Why could this be happening?
During the initialization phase, some variables are going to be null since it hasn't been reached in the call order. RadioButton_Checked is called through event before the button is constructed since it contains the Checked property.
A quick and easy fix is as follows: Check for null in your event calls.
private void RadioButton_Checked (object sender, RoutedEventArgs e)
{
if(MainButton != null)
MainButton.Content = "Set output to red";
}
private void RadioButton_Checked_1 (object sender, RoutedEventArgs e)
{
if (MainButton != null)
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Of course, there are better ways to handle this. You could set checked on a separate event, Initialized, which will handle it much cleaner.

Change color from another class is not working

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xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
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MyView.xaml file
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xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:ViewModel="clr-namespace:WpfApp1.ViewModel"
xmlns:View="clr-namespace:WpfApp1.View">
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{
get { return new MyCommand(ChangeColor); }
}
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MessageBox.Show("Color before: " + MainCanvas.Background.ToString());
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MessageBox.Show("Color after: " + MainCanvas.Background.ToString());
}
}
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Xaml:
<Canvas Name="MainCanvas" Height="300" Width="502" Background="{Binding BackGroundColor}">
<Button Name="ChangeColorButton" Command="{Binding CommandChangeColor}" Content="new color" Height="25" Width="55" Margin="225,268,225,10"/>
</Canvas>
MyClass.cs
public SolidColorBrush BackGroundColor {get;set;}
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{
MessageBox.Show("Color before: " + MainCanvas.Background.ToString());
Random rnd = new Random();
int i = rnd.Next(_listOfColors.Count - 1);
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MessageBox.Show("Color after: " + MainCanvas.Background.ToString());
}
You will probably also want to implement INotifyPropertyChanged.

Get ListViewItem text by index WP RT

How do I get a ListViewItem text by this item index? I tried this
txt = historico.Items[i].ToString();
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"Windows.UI.Xaml.Controls.ListViewItem"
In the MainPage.xaml:
<Page
x:Class="PushNotification_Sampl.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
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And in MainPage.xaml.cs, I have added the click event for the button:
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This works well in Windows Phone 8.1 app. Successfully tested. Hope this helps.
txt = (historico.Items[i] as ListViewItem).Content.ToString();
or
txt = (historico.Items[i] as ListViewItem).Text;
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WPF : Move control c# code to change position from location to another

how can move (change position) label from position to another using wpf **
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xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
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{
public MainWindow()
{
InitializeComponent();
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{
var storyboard = new Storyboard();
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and the code behind doesn't do much:
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Old code:
...
StackPanel sp = new StackPanel();
sp.Add(new CheckBox());
somewhere.Add(sp);
...
--> I see a checkbox
New code:
...
somewhere.Add(new CustomStackPanel());
...
--> No checkbox

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