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How do I update an ObservableCollection via a worker thread?
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Closed 5 years ago.
I try to do some simple task (I guess so). I want to change GUI dynamically, from the for loop.
Let's see my XAML:
<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">
<StackPanel Name="MyPanel">
<TextBlock Text="{Binding MyValue}"></TextBlock>
<Button Click="Button_Click">OK</Button>
<ListBox Name="myList" ItemsSource="{Binding MyCollection}" >
<ListBox.ItemTemplate>
<DataTemplate>
<Grid Margin="10">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="20"/>
<ColumnDefinition Width="20"/>
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding A}" Grid.Column="0"/>
<TextBlock Text="{Binding B}" Grid.Column="1"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</StackPanel>
</Window>
As you can see, I have the Textblock that shows numbers, button that is starting the program and the listbox, that should show the collection items.
After click on the button, the first textblock (bindes MyValue) shows dynamic values, but on the list box I get the next error:
"This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread."
I saw another answers for the error, but cannot understand how to implement it in my case.
Here the C# code:
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
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 static MyModel m;
public MainWindow()
{
m = new MyModel();
InitializeComponent();
MyPanel.DataContext = m;
}
bool flag = false;
private void Button_Click(object sender, RoutedEventArgs e)
{
flag = !flag;
Task.Factory.StartNew(() =>
{
for (int i = 0; i < 5000000; i++)
{
if (flag == false) break;
m.MyValue = i.ToString();
m.MyCollection.Add(new ChartPoint { A = i, B = 2 * i });
}
});
}
}
public class MyModel : INotifyPropertyChanged
{
private string myValue;
public ObservableCollection<ChartPoint> MyCollection { get; set; }
public MyModel()
{
MyCollection = new ObservableCollection<ChartPoint>();
}
public string MyValue
{
get { return myValue; }
set
{
myValue = value;
RaisePropertyChanged("MyValue");
}
}
private void RaisePropertyChanged(string propName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propName));
}
public event PropertyChangedEventHandler PropertyChanged;
}
public class ChartPoint
{
public int A { get; set; }
public int B { get; set; }
}
}
Thanks a lot!
I have changed the Button_Click code a bit, is this you want to achieve, please suggest:
private void Button_Click(object sender, RoutedEventArgs e)
{
flag = !flag;
var list = new List <ChartPoint>();
Task.Factory.StartNew(() =>
{
for (int i = 0; i < 50000000; i++)
{
if (flag == false) break;
m.MyValue = i.ToString();
Dispatcher.BeginInvoke(new Action(() =>
{
m.MyCollection.Add(new ChartPoint
{
A = i,
B = 2 * i
});
}),
DispatcherPriority.Background);
}
});
}
Related
Im quite new to coding. So far I have a WPF application that when I press submit it creates the treeview but I wanted to add a countdown timer for each child item and have it display the time remaining next to the child item. The problem is the treeview doesn't update and I dont know how to assign a timer for each child item
using Microsoft.Azure.Cosmos.Core.Collections;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Timers;
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.Windows.Threading;
namespace Test_v2
{
public partial class MainWindow : Window
{
public int secondsCount = 100;
public MainWindow()
{
InitializeComponent();
DispatcherTimer disTmr = new DispatcherTimer();
disTmr.Tick += new EventHandler(disTmr_Tick);
disTmr.Interval = new TimeSpan(0, 0, 1);
disTmr.Start();
}
public void disTmr_Tick(object sender, EventArgs e)
{
secondsCount--;
}
List<TreeViewItem> folderList = new List<TreeViewItem>();
public void SubmitButton_Click(object sender, RoutedEventArgs e)
{
if (Folder.Text.Length == 0)
{
ErrorBlock.Text = "Please Enter Folder Name";
return;
}
if (Name.Text.Length == 0)
{
ErrorBlock.Text = "Please Enter a Name";
return;
}
TreeViewItem parent = new TreeViewItem();
for (int i = 0; i < folderList.Count; i++)
{
if (folderList[i].Header.ToString() == Folder.Text)
{
parent = folderList[i];
break;
}
}
if (folderList.Contains(parent))
{
FolderInArrayBlock.Text = "True";
TreeViewItem newChild = new TreeViewItem();
newChild.Header = Name.Text + secondsCount.ToString();
parent.Items.Add(newChild);
}
else
{
FolderInArrayBlock.Text = "false";
TreeViewItem? treeItem = null;
treeItem = new TreeViewItem();
treeItem.Header = Folder.Text;
folderList.Add(treeItem);
treeItem.Items.Add(new TreeViewItem() { Header = Name.Text + secondsCount.ToString()});
LearningItems.Items.Add(treeItem);
}
}
}
}
First of all, if you are using Wpf, you need to use MVVM approch if you want to make a sustainable and maintainable code. This means you need to seperate View funcionalities from Model funcionalities and use a ViewModel as a bridge to be able to communicate with those two things. In Wpf we should try to use Bindings and notifypropertychange to build the brige between View and ViewModel and not use control naming for later use in code behind .cs.(Code behind is the .cs file which belongs to .xaml file ex.: MainWindow.xaml.cs)
I recommend you to take a look at this page, which explains why its so important to use MVVM in your Wpf applications: MVVM pattern
I have created a sample project which demonstrate a proper approch for your task, in my opinion.
MainWindow.xaml
<Window x:Class="TreeViewWithCountDown.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:TreeViewWithCountDown"
xmlns:localviewmodels="clr-namespace:TreeViewWithCountDown.ViewModels"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Grid>
<TreeView ItemsSource="{Binding Path=Items, Mode=OneWay}">
<!--We use TreeView Resources because we bind Items as ItemSource and Items is a List of StorageItems, which can be either FolderItem or FileItem.
TreeView can display the two types differently if we specify in the Resources-->
<TreeView.Resources>
<!--Here we specify how to display a FolderItem-->
<HierarchicalDataTemplate DataType="{x:Type localviewmodels:FolderItem}"
ItemsSource="{Binding Path=Items}">
<TextBlock Text="{Binding Path=Name}"
Margin="0 0 35 0"/>
</HierarchicalDataTemplate>
<!--Here we specify how to display a FileItem-->
<DataTemplate DataType="{x:Type localviewmodels:FileItem}">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" SharedSizeGroup="FileNames"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding Path=Name}"
Margin="0 0 35 0"
Grid.Column="0"/>
<TextBlock Text="{Binding Path=CountdownTime}"
Margin="0 0 15 0"
Grid.Column="1">
</TextBlock>
</Grid>
</DataTemplate>
</TreeView.Resources>
</TreeView>
</Grid>
MainWindow.xaml.cs
using System.Windows;
namespace TreeViewWithCountDown
{
public partial class MainWindow : Window
{
private ViewModel _viewModel= new ViewModel();
public MainWindow()
{
InitializeComponent();
//Really important to define where to look for the binding properties
DataContext = _viewModel;
}
}
}
ViewModel.cs
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Timers;
using TreeViewWithCountDown.ViewModels;
namespace TreeViewWithCountDown
{
public class ViewModel : INotifyPropertyChanged
{
private List<StorageItem> _items = new List<StorageItem>();
public List<StorageItem> Items
{
get => _items;
set
{
if (_items != value)
{
_items = value;
OnPropertyChanged();
}
}
}
public ViewModel()
{
//Filling up our Items property which will be given to the View for display
Random random = new Random();
FileItem item0 = new FileItem("file0", random.Next(0,100));
FolderItem item1 = new FolderItem("folder1");
item1.Items.Add(item0);
FileItem item2 = new FileItem("file2", random.Next(0, 100));
FileItem item3 = new FileItem("file3", random.Next(0, 100));
Timer timer = new Timer(3000);
timer.Elapsed += Time_Elapsed;
timer.Start();
Items.Add(item1);
Items.Add(item2);
Items.Add(item3);
}
private void Time_Elapsed(object sender, ElapsedEventArgs e)
{
foreach (StorageItem item in Items)
{
if (item is FileItem fileItem)
{
fileItem.CountdownTime--;
}
else
{
//Reducing counters of Files in Folders
ReduceFileCountInFolders(item);
}
}
}
//A file can be nested in multiple folders so we can solve this with a recursive method
private void ReduceFileCountInFolders(StorageItem item)
{
if (item is FileItem fileItem)
{
fileItem.CountdownTime--;
}
else if (item is FolderItem folderItem)
{
if (folderItem.Items != null && folderItem.Items.Count > 0)
{
foreach (StorageItem storageItem in folderItem.Items)
{
ReduceFileCountInFolders(storageItem);
}
}
}
}
protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
try
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
catch (Exception ex)
{
throw new Exception($"PropertyChanged event handler FAILED : {ex.Message}");
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
}
StorageItem.cs
using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;
namespace TreeViewWithCountDown.ViewModels
{
public class StorageItem : INotifyPropertyChanged
{
private string _name;
public string Name
{
get => _name;
set
{
if (_name != value)
{
_name = value;
OnPropertyChanged();
}
}
}
public StorageItem(string name)
{
Name = name;
}
protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
try
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
catch (Exception ex)
{
throw new Exception($"PropertyChanged event handler FAILED : {ex.Message}");
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
}
FileItem.cs
namespace TreeViewWithCountDown.ViewModels
{
public class FileItem : StorageItem
{
private int _countdownTime;
public int CountdownTime
{
get => _countdownTime;
set
{
if (_countdownTime != value && value > 0)
{
_countdownTime = value;
OnPropertyChanged();
}
}
}
public FileItem(string name, int num) : base(name)
{
CountdownTime = num;
}
}
}
FolderItem.cs
using System.Collections.Generic;
namespace TreeViewWithCountDown.ViewModels
{
public class FolderItem : StorageItem
{
private List<StorageItem> _items = new List<StorageItem>();
public List<StorageItem> Items
{
get => _items;
set
{
if (_items != value)
{
_items = value;
OnPropertyChanged();
}
}
}
public FolderItem(string name) : base(name)
{
}
}
}
The final look: View
Hope this will help, if anything seems complicated, feel free to ask!
Very new to WPF coding using MVVM. Tried making a simple calculator in WPF using MVVM. But unable to trigger the Icommand in the below code.If possible help me in this. Grateful if anybody can help me out.
View Code:
<Window x:Class="MVVMCalculator.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:MVVMCalculator"
mc:Ignorable="d"
Title="Calculator" Height="350" Width="300">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="85"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBox Text="{Binding Display, Mode=OneWay}" IsReadOnly="True" TextWrapping="Wrap"
Grid.Row="0" Background="#E2E2E2" Margin="0,10,0,0" VerticalAlignment="Top"
Height="75" Width="250" HorizontalAlignment="Center" FontSize="22" FontWeight="Bold"
TextAlignment="Right">
<TextBox.Effect>
<DropShadowEffect/>
</TextBox.Effect>
</TextBox>
<ItemsControl Grid.Row="1" ItemsSource="{Binding Buttns}" Margin="15,15,15,10">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<UniformGrid Columns="5" Rows="4" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Button Content="{Binding Txt, Mode=TwoWay}" Command="{Binding Enter_number}"
FontSize="18" FontWeight="Bold" Height="50" Width="50" Background="#eef2f3"
BorderBrush="Black" BorderThickness="1.0" Name="number">
<Button.Effect>
<DropShadowEffect/>
</Button.Effect>
</Button>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
</Window>
ViewModel Code:
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;
namespace MVVMCalculator
{
class ViewModel : INotifyPropertyChanged
{
Buttons btn = new Buttons();
private decimal operand1;
private decimal operand2;
private string operation;
private decimal result;
private string display;
private bool newDisplayRequired = false;
ObservableCollection<Buttons> buttns;
public ObservableCollection<Buttons> Buttns
{
get { return buttns; }
set { buttns = value; }
}
public decimal Result
{
get { return result; }
}
public decimal Operand1
{
get { return operand1; }
set { operand1 = value; }
}
public decimal Operand2
{
get { return operand2; }
set { operand2 = value; }
}
public string Operation
{
get { return operation; }
set { operation = value; }
}
public string Display
{
get { return display; }
set { display = value;
OnPropertyChanged("Display");
}
}
public ViewModel()
{
buttns = new ObservableCollection<Buttons>
{
new Buttons("1"), new Buttons("2"), new Buttons("3"),
new Buttons("C"), new Buttons("Back"), new Buttons("4"),
new Buttons("5"), new Buttons("6"), new Buttons("CE"),
new Buttons("%"), new Buttons("7"), new Buttons("8"),
new Buttons("9"), new Buttons("/"), new Buttons("*"),
new Buttons("0"), new Buttons("."), new Buttons("+"),
new Buttons("-"), new Buttons("=")
};
display = "0";
operand1 = 0;
operand2 = 0;
operation = "";
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
private ICommand enter_number;
public ICommand Enter_number
{
get
{
if(enter_number==null)
{
enter_number = new DelegateCommand<string>(MyAction, _canExecute);
}
return enter_number;
}
}
private static bool _canExecute(string button)
{
return true;
}
public void MyAction(string btn)
{
switch(btn)
{
case "C":
display = "0";
operand1 = 0;
operand2 = 0;
//operation = "";
break;
case ".":
if (!display.Contains("."))
{
Display = display + ".";
}
break;
case "Back":
if (display.Length > 1)
Display = display.Substring(0, display.Length - 1);
else Display = "0";
break;
default:
if (display == "0" || newDisplayRequired)
Display = btn;
else
Display = display + btn;
break;
}
}
}
}
Buttons Class:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace MVVMCalculator
{
class Buttons:INotifyPropertyChanged
{
private string txt;
public string Txt
{
get { return txt; }
set { txt = value; }
}
public Buttons(string a)
{
txt = a;
}
public Buttons()
{
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
}
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 MVVMCalculator
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
this.DataContext = new ViewModel();
}
}
}
Since the Enter_number property is defined in the ViewModel class you need to use a {RelativeSource} to be able to bind to it:
<Button Content="{Binding Txt, Mode=TwoWay}"
Command="{Binding DataContext.Enter_number, RelativeSource={RelativeSource AncestorType=ItemsControl}}"
FontSize="18" FontWeight="Bold" Height="50" Width="50" Background="#eef2f3"
BorderBrush="Black" BorderThickness="1.0" Name="number">
<Button.Effect>
<DropShadowEffect/>
</Button.Effect>
</Button>
The default DataContext of the Button is the current Buttons object in the ItemsSource collection of the ItemsControl and that's why your binding fails.
In my windows phone application, I have list that have all contacts like below:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Navigation;
using Microsoft.Phone.Controls;
using Microsoft.Phone.Shell;
using GetContacts.Resources;
using Microsoft.Phone.UserData;
using Microsoft.Phone.Tasks;
using Windows.Phone.PersonalInformation;
using System.IO.IsolatedStorage;
namespace GetContacts
{
public partial class MainPage : PhoneApplicationPage
{
List<CustomContact> listOfContact = new List<CustomContact>();
public MainPage()
{
InitializeComponent();
// Sample code to localize the ApplicationBar
//BuildLocalizedApplicationBar();
}
private void ButtonContacts_Click(object sender, RoutedEventArgs e)
{
Contacts cons = new Contacts();
cons.SearchCompleted += new EventHandler<ContactsSearchEventArgs>(Contacts_SearchCompleted);
cons.SearchAsync(String.Empty, FilterKind.None, "Contacts Test #1");
}
void Contacts_SearchCompleted(object sender, ContactsSearchEventArgs e)
{
listOfContact.Clear();
try
{
foreach (var c in e.Results)
{
CustomContact contact = new CustomContact();
contact.Name = c.DisplayName;
int count = c.PhoneNumbers.Count();
for (int i = 0; i < count; i++)
{
if (count > 0 && c.PhoneNumbers.ElementAt(i).PhoneNumber != null && !string.IsNullOrEmpty(c.PhoneNumbers.ElementAt(i).PhoneNumber) )
{
contact.Number[i]= c.PhoneNumbers.ElementAt(i).PhoneNumber.ToString();//.ToString();
}
else
{
contact.Number[i] = "";
}
}
listOfContact.Add(contact);
}
for (int i = 0; i < listOfContact.Count(); i++)
{
if(listOfContact1.Count != listOfContact.Count)
{
listOfContact1.Add(listOfContact.ElementAt(i));
}
}
ContactResultsData.ItemsSource = listOfContact;
}
catch (System.Exception)
{
//No results
}
if (ContactResultsData.Items.Any())
{
ContactResultsLabel.Text = "results";
}
else
{
ContactResultsLabel.Text = "no results";
}
}
private void hyplnk_Next_Click(object sender, RoutedEventArgs e)
{
PhoneApplicationService.Current.State["Contact"] = listOfContact;
NavigationService.Navigate(new Uri("/createGroups.xaml?Contact=" + listOfContact, UriKind.Relative));
}
}
}
below is the CustomContact class:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Navigation;
using Microsoft.Phone.Controls;
using Microsoft.Phone.Shell;
using GetContacts.Resources;
using Microsoft.Phone.UserData;
using System.IO;
using System.Xml.Serialization;
namespace GetContacts
{
public class CustomContact
{
public string[] number = new string[5];
public string Name { get; set; }
public string[] Number
{
get { return number; }
set { number = value; }
}
public CustomContact()
{
}
public CustomContact( Contact contact)
{
Name = contact.DisplayName;
int count = contact.PhoneNumbers.Count();
for (int i = 0; i < count; i++)
{
if (count > 0 && contact.PhoneNumbers.ElementAt(i).PhoneNumber != null && !string.IsNullOrEmpty(contact.PhoneNumbers.ElementAt(i).PhoneNumber))
{
Number[i] = contact.PhoneNumbers.ElementAt(i).PhoneNumber.ToString();
}
else
{
Number[i] = "";
}
}
}
}
}
below is XAML page
<Grid x:Name="ContentPanel" Margin="12,0,12,0">
<StackPanel Height="Auto" Width="Auto" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Margin="0,0,0,10">
<TextBlock x:Name="ContactResultsLabel" Text="results are loading..." Style="{StaticResource PhoneTextLargeStyle}" TextWrapping="Wrap" />
<ListBox x:Name="ContactResultsData" ItemsSource="{Binding listOfContacts}" Height="293" Margin="24,0,0,0" >
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock x:Name="ContactResultsName" Text="{Binding Name}" FontSize="50" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</StackPanel>
</Grid>
<Grid Grid.Row="1">
<Button x:Name="ButtonContacts"
Content="Get All Contacts"
FontSize="15"
Width="200"
Height="70"
Background="AliceBlue"
Foreground="Blue"
HorizontalAlignment="Left"
Click="ButtonContacts_Click" Margin="27,30,0,322"></Button>
</Grid>
And in the hyplnk_Next_Click event, I navigate list to the next page but when I come back to the previous page the items of list are lost and the list is empty. what should I do to maintain the list of elements after navigation. Kindly suggest me.
Waiting for your reply.
Thanks.
You already save the transientState (the CustomContancts list), although your hyperlinkbutton handler is not the place to do it. I presume you're not loading it after you navigate back to the page with the contacts.
You should read and understand the Application Execution Model. It is crucial in Windows Phone development.
The place to save and load your page's state are the page's overriden methods OnNavigatedFrom OnNavigatedTo.
Here's an example
protected override void OnNavigatedTo(NavigationEventArgs e)
{
base.OnNavigatedTo(e);
if (PhoneApplicationService.Current.State.Contains["Contact"])
{
listOfContact =
PhoneApplicationService.Current.State["Contact"] as List<CustomContact>();
}
}
protected override void OnNavigatedFrom(NavigationEventArgs e)
{
base.OnNavigatedFrom(e);
PhoneApplicationService.Current.State["Contact"] = listOfContact;
}
OnNavigatedFrom is called whenever you navigate away from a page and OnNavigatedTo is called when you navigate to a page.
I am making a wpf application that has 2 datagrids and I want them to scroll together.
I know that the DataGridView class has a scroll event that you can use make the necessary changes to the other grid, but DataGrids don't have a Scroll event. I MUST use a DataGrid.
This example is good but is not WPF and it's using DataGridView instead of DataGrid. Using one scroll bar to control two DataGridView
What is the best way to have it so that one data grid's scroll bar also will move the data grid's scroll bar in WPF and DataGrids?
You can do this by getting the underlying ScrollViewer of both DataGrid's and setting up the event accordingly. Below is a quick example I made that appears to work as you've described.
xaml:
<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" Loaded="Window_Loaded">
<Grid>
<DataGrid AutoGenerateColumns="True" Height="200" HorizontalAlignment="Left" Margin="52,69,0,0" Name="dataGrid1" VerticalAlignment="Top" Width="200" ItemsSource="{Binding Collection}" />
<DataGrid AutoGenerateColumns="True" Height="200" HorizontalAlignment="Left" Margin="270,69,0,0" Name="dataGrid2" VerticalAlignment="Top" Width="200" ItemsSource="{Binding Collection}" />
</Grid>
</Window>
code behind:
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;
using System.Collections.ObjectModel;
namespace WpfApplication1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
ObservableCollection<Person> _collection = new ObservableCollection<Person>();
ScrollViewer scrollView = null;
ScrollViewer scrollView2 = null;
public MainWindow()
{
for (int i = 0; i < 50; i++)
{
var p = new Person() { Name = string.Format("{0}", i), Age = i };
_collection.Add(p);
}
this.DataContext = this;
InitializeComponent();
}
void scrollView_ScrollChanged(object sender, ScrollChangedEventArgs e)
{
var newOffset = e.VerticalOffset;
if ((null != scrollView) && (null != scrollView2))
{
scrollView.ScrollToVerticalOffset(newOffset);
scrollView2.ScrollToVerticalOffset(newOffset);
}
}
public ObservableCollection<Person> Collection
{
get
{
return _collection;
}
}
private ScrollViewer getScrollbar(DependencyObject dep)
{
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(dep); i++)
{
var child = VisualTreeHelper.GetChild(dep, i);
if ((null != child) && child is ScrollViewer)
{
return (ScrollViewer)child;
}
else
{
ScrollViewer sub = getScrollbar(child);
if (sub != null)
{
return sub;
}
}
}
return null;
}
private void Window_Loaded(object sender, RoutedEventArgs e)
{
scrollView = getScrollbar(dataGrid1);
scrollView2 = getScrollbar(dataGrid2);
if (null != scrollView)
{
scrollView.ScrollChanged += new ScrollChangedEventHandler(scrollView_ScrollChanged);
}
if (null != scrollView2)
{
scrollView2.ScrollChanged += new ScrollChangedEventHandler(scrollView_ScrollChanged);
}
}
}
public class Person
{
public string Name { get; set; }
public int Age { get; set; }
}
}
What is happening is that I'm iterating through the VisualTree of both DataGrids upon Window load using getScrollbar. I then set up the scroll changed event for both DataGrids and then scroll to the vertical offset that was just changed inside the scroll changed event handler.
I'm populating a listBox, Each list item has a button.
I've got it populating text in to the list, but I'd like each button to have the correct event handler and the house number to be passed to it.
Here's the XAML code:
<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" Loaded="Window_Loaded" Background="#FFCBCBCB">
<Grid>
<Label Content="Welcome to the house manager" Height="28" HorizontalAlignment="Left" Margin="20,12,0,0" Name="label1" VerticalAlignment="Top" />
<ListBox Height="253" HorizontalAlignment="Left" Margin="10,46,0,0" VerticalAlignment="Top" Width="481" x:Name="houseList">
<ListBox.ItemTemplate>
<DataTemplate DataType="house">
<Button Click="choose_house(HOUSE NUMBER HERE)" Background="#FFBEBEBE" BorderThickness="0" Focusable="True" Width="459" BorderBrush="White" Padding="0">
<StackPanel Orientation="Vertical" Width="400" VerticalAlignment="Stretch">
<TextBlock Margin="0,5,0,0" Text="{Binding street}" HorizontalAlignment="Left" />
<TextBlock Margin="0,5,0,0" Text="{Binding postCode}" HorizontalAlignment="Left" />
</StackPanel>
</Button>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
</Window>
Here's the code which populates the list at the moment:
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 WpfApplication1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void Window_Loaded(object sender, RoutedEventArgs e)
{
List<house> houseAddresses = new List<house>();
// Create a new house
for (var i = 1; i <= 10; i++)
{
house newHouse = new house();
newHouse.street = i + " Scale Hall Lane";
newHouse.postCode = "PR4 3TL";
newHouse.houseNumber = i;
houseAddresses.Add(newHouse);
}
// Go through each house and add them to the list
foreach (house houses in houseAddresses)
{
houseList.Items.Add(houses);
}
}
private void choose_house(object sender, RoutedEventArgs e)
{
MessageBox.Show("Clicked");
}
}
}
Here's my house class:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace WpfApplication1
{
class house
{
public string street { get; set; }
public string postCode { get; set; }
public int houseNumber { get; set; }
}
}
I've put Click="choose_house(HOUSE NUMBER HERE)" in the code on the button where the code would have the correct event handler.
Either cast your sender as a Button and get it's DataContext, or use a Command and bind the CommandParameter to the HouseNumber
private void choose_house(object sender, RoutedEventArgs e)
{
var ctrl = sender as Button;
var h = ctrl.DataContext as house; // Please capitalize your classes! :)
MessageBox.Show(h.houseNumber);
}
or
<Button Command="{Binding Path=DataContext.ChooseHouseCommand,
RelativeSource={RelativeSource AncestorType={x:Type ListBox}}}"
CommandParameter="{Binding houseNumber}" ... />
What you can do on the click handler is:
private void choose_house(object sender, RoutedEventArgs e)
{
var button = sender as Button;
if (button != null)
{
var yourObject = button.DataContext as house;
if (yourObject != null)
{
//do stuff with your button
}
}
}