Wpf Databinding with ViewModel as property

Wpf Databinding with ViewModel as property - c#

to keep my MainWindow.xaml.cs clean I tried to outsource everything to a ViewModel class and then bind my view to properties of my ViewModel property
However using this extra layer doesn't seem to work. My List- and Textbox just stay empty. Any way to get this method working?
MainWindow class:
public partial class MainWindow : Window, INotifyPropertyChanged
{
public ViewModel ViewModel { get; set; }
public MainWindow()
{
InitializeComponent();
ViewModel = new ViewModel();
}
}
ViewModel class:
public class ViewModel : INotifyPropertyChanged
{
private string m_oneLineOnly;
private ObservableCollection<string> m_sampleLines;
public ObservableCollection<string> SampleLines
{
get => m_sampleLines;
set
{
m_sampleLines = value;
RaisePropertyChanged(nameof(SampleLines));
}
}
public string OneLineOnly
{
get => m_oneLineOnly;
set
{
m_oneLineOnly = value;
RaisePropertyChanged(nameof(OneLineOnly));
}
}
public ViewModel()
{
SampleLines = new ObservableCollection<string>(new List<string>()
{
"Gedanken",
"Zeit",
"Sand"
});
OneLineOnly = "Hello World";
}
public event PropertyChangedEventHandler PropertyChanged = delegate { };
private void RaisePropertyChanged(string propertyName)
{
var handlers = PropertyChanged;
handlers(this, new PropertyChangedEventArgs(propertyName));
}
}
MainWindow XAML
<Window x:Class="DataContext_Test_Project.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:DataContext_Test_Project"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800"
x:Name="Window">
<Grid>
<ListBox
HorizontalAlignment="Left"
Height="100"
Margin="334,132,0,0"
VerticalAlignment="Top"
Width="100"
ItemsSource="{Binding ElementName=Window, Path=ViewModel.SampleLines}"/>
<TextBox
HorizontalAlignment="Left"
Height="23"
Margin="184,166,0,0"
TextWrapping="Wrap"
VerticalAlignment="Top"
Width="120"
DataContext="{Binding ElementName=Window, Path=ViewModel}"
Text="{Binding Path=OneLineOnly}"/>
</Grid>

You can also define the DataContext in code behind:
public partial class MainWindow : Window
{
public ViewModel ViewModel { get; set; }
public MainWindow()
{
InitializeComponent();
ViewModel = new ViewModel();
DataContext = ViewModel;
}
}
And clean your XAML:
<Grid>
<ListBox
HorizontalAlignment="Left"
Height="100"
Margin="334,132,0,0"
VerticalAlignment="Top"
Width="100"
ItemsSource="{Binding SampleLines}"/>
<TextBox
HorizontalAlignment="Left"
Height="23"
Margin="184,166,0,0"
TextWrapping="Wrap"
VerticalAlignment="Top"
Width="120"
Text="{Binding OneLineOnly}"/>
</Grid>

In order to make Bindings like
ItemsSource="{Binding ElementName=Window, Path=ViewModel.SampleLines}"
DataContext="{Binding ElementName=Window, Path=ViewModel}"
work, you have two options. Either make the ViewModel property fire a property change notification, or simply initialize it before the XAML is parsed, i.e. before InitializeComponent() is called:
Like this:
public partial class MainWindow : Window
{
public ViewModel ViewModel { get; }
public MainWindow()
{
ViewModel = new ViewModel();
InitializeComponent();
}
}
Or simpler:
public partial class MainWindow : Window
{
public ViewModel ViewModel { get; } = new ViewModel();
public MainWindow()
{
InitializeComponent();
}
}

Remove the following line from xaml.cs file : ViewModel = new ViewModel();
Use the following code for Xaml file:
<Window x:Class="DataContext_Test_Project.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:DataContext_Test_Project"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800"
x:Name="Window" DataContext="{DynamicResource ViewModel}">
<Window.Resources>
<local:ViewModel x:Key="ViewModel"/>
</Window.Resources>
<Grid>
<ListBox
HorizontalAlignment="Left"
Height="100"
Margin="334,132,0,0"
VerticalAlignment="Top"
Width="100"
ItemsSource="{Binding Path=SampleLines}"/>
<TextBox
HorizontalAlignment="Left"
Height="23"
Margin="184,166,0,0"
TextWrapping="Wrap"
VerticalAlignment="Top"
Width="120"
Text="{Binding Path=OneLineOnly}"/>
</Grid>
</Window>

Related

Switch between views without losing data in WPF

I am working on a project that has one Main Window and two User Controls (Views).
The Main Window has a Menu on the left hand side with some buttons that activate one View or the other. On the right hand side of Main Window there's a Content Control that displays the CurrentView.
My idea was to have a Form for adding people on one View and a DataGrid displaying those people on the other. For that I made an ObservableColection that has People and bound that collection to the DataGrid on the corresponding View.
Everything is working as intended (with the Form I can add people to the collection and then those people get added to the DataGrid) except that when I add a person and then change the View to see if it got added to the DataGrid, nothing is added to the DataGrid but the headers.
If I put the same DataGrid with the same Binding in the first View (where the Form is) I can see that the people are getting added so I think the problem is that when I change Views I am losing the information about the collection.
``
This is the code I'm using to make the navigation between views available.
MainWindow
<Window x:Class="SwitchViewsDemo2.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:vm="clr-namespace:SwitchViewsDemo2.ViewModels"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Window.DataContext>
<vm:NavigationViewModel/>
</Window.DataContext>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="180"/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<StackPanel VerticalAlignment="Center">
<Button Command="{Binding GoToAddPeopleCommand}" Content="Go To Add People" />
<Button Command="{Binding GoToDisplayPeopleCommand}" Content="Go To Display People" />
</StackPanel>
<ContentControl Grid.Column="1" Content="{Binding CurrentView}" />
</Grid>
</Window>
AddPeopleView
<UserControl x:Class="SwitchViewsDemo2.Views.AddPeopleView"
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:vm="clr-namespace:SwitchViewsDemo2.ViewModels"
mc:Ignorable="d" FontSize="28"
d:DesignHeight="450" d:DesignWidth="800">
<UserControl.DataContext>
<vm:AddPeopleViewModel/>
</UserControl.DataContext>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="1*"/>
<RowDefinition Height="2*"/>
</Grid.RowDefinitions>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<TextBlock Text="Add People" />
<StackPanel VerticalAlignment="Center" HorizontalAlignment="Center">
<TextBlock Text="First Name" />
<TextBox Text="{Binding FirstName}"/>
</StackPanel>
<StackPanel VerticalAlignment="Center" HorizontalAlignment="Center" Grid.Column="1">
<TextBlock Text="Last Name" />
<TextBox Text="{Binding LastName}"/>
</StackPanel>
</Grid>
<StackPanel Grid.Row="1">
<Button Content="Add Person" Command="{Binding AddPersonCommand}"
Height="40" Width="200" VerticalAlignment="Top"/>
<DataGrid ItemsSource="{Binding People}"/>
</StackPanel>
</Grid>
</UserControl>
DisplayPeopleView
<UserControl x:Class="SwitchViewsDemo2.Views.DisplayPeopleView"
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:vm="clr-namespace:SwitchViewsDemo2.ViewModels"
mc:Ignorable="d" FontSize="28"
d:DesignHeight="450" d:DesignWidth="800">
<UserControl.DataContext>
<vm:DisplayPeopleViewModel/>
</UserControl.DataContext>
<Grid>
<StackPanel>
<TextBlock Text="Display People"/>
<DataGrid ItemsSource="{Binding People}"/>
</StackPanel>
</Grid>
</UserControl>
NavigationViewModel
using SwitchViewsDemo2.Utilities;
using System.Windows.Input;
namespace SwitchViewsDemo2.ViewModels
{
public class NavigationViewModel : Utilities.ViewModelBase
{
private object _currentView;
public object CurrentView
{
get { return _currentView; }
set { _currentView = value; OnPropertyChanged(); }
}
public ICommand GoToAddPeopleCommand { get; set; }
public ICommand GoToDisplayPeopleCommand { get; set; }
private void AddPeople(object obj) => CurrentView = new AddPeopleViewModel();
private void DisplayPeople(object obj) => CurrentView = new DisplayPeopleViewModel();
public NavigationViewModel()
{
GoToAddPeopleCommand = new RelayCommand(AddPeople);
GoToDisplayPeopleCommand = new RelayCommand(DisplayPeople);
// Startup View
CurrentView = new AddPeopleViewModel();
}
}
}
ViewModelBase
using SwitchViewsDemo2.Models;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Runtime.CompilerServices;
namespace SwitchViewsDemo2.Utilities
{
public class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler? PropertyChanged;
public void OnPropertyChanged([CallerMemberName] string propName = null) =>
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));
private ObservableCollection<PersonModel> _people = new();
public ObservableCollection<PersonModel> People
{
get { return _people; }
set { _people = value; }
}
}
}
RelayCommand
using System;
using System.Windows.Input;
namespace SwitchViewsDemo2.Utilities
{
public class RelayCommand : ICommand
{
private readonly Action<object> _execute;
private readonly Func<object, bool> _canExecute;
public event EventHandler? CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public RelayCommand(Action<object> execute, Func<object, bool> canExecute = null)
{
_execute = execute;
_canExecute = canExecute;
}
public bool CanExecute(object? parameter) => _canExecute == null || _canExecute(parameter);
public void Execute(object? parameter) => _execute(parameter);
}
}
DataTemplate(Resource Dictionary)
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vm="clr-namespace:SwitchViewsDemo2.ViewModels"
xmlns:view="clr-namespace:SwitchViewsDemo2.Views">
<DataTemplate DataType="{x:Type vm:AddPeopleViewModel}">
<view:AddPeopleView/>
</DataTemplate>
<DataTemplate DataType="{x:Type vm:DisplayPeopleViewModel}">
<view:DisplayPeopleView/>
</DataTemplate>
</ResourceDictionary>
App.xaml
<Application x:Class="SwitchViewsDemo2.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:SwitchViewsDemo2"
StartupUri="MainWindow.xaml">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="Utilities/DataTemplate.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
</Application>
Edit:
This is how I add the data to the People object
using SwitchViewsDemo2.Models;
using SwitchViewsDemo2.Utilities;
namespace SwitchViewsDemo2.ViewModels
{
public class AddPeopleViewModel : ViewModelBase
{
private string _firstName;
public string FirstName
{
get { return _firstName; }
set { _firstName = value; OnPropertyChanged(); }
}
private string _lastName;
public string LastName
{
get { return _lastName; }
set { _lastName = value; OnPropertyChanged(); }
}
public ButtonCommand AddPersonCommand { get; set; }
public void AddPerson()
{
PersonModel p = new PersonModel()
{
FirstName = FirstName,
LastName = LastName
};
FirstName = string.Empty;
LastName = string.Empty;
People.Add(p);
}
public AddPeopleViewModel()
{
AddPersonCommand = new ButtonCommand(AddPerson);
}
}
}
ButtonCommand:
using System;
using System.Windows.Input;
namespace SwitchViewsDemo2.Utilities
{
public class ButtonCommand : ICommand
{
public event EventHandler? CanExecuteChanged;
private Action _execute;
public ButtonCommand(Action execute)
{
_execute = execute;
}
public bool CanExecute(object? parameter)
{
return true;
}
public void Execute(object? parameter)
{
_execute.Invoke();
}
}
}

Remove this:
<UserControl.DataContext>
<vm:AddPeopleViewModel/>
</UserControl.DataContext>
...and this:
<UserControl.DataContext>
<vm:DisplayPeopleViewModel/>
</UserControl.DataContext>
from the XAML markup of the views.
You are creating the AddPeopleViewModel and DisplayPeopleViewModel instances in the NavigationViewModel. You should not create additional instances of the view models in the views.
It's also unclear why're expecting adding an object to a collection in one view model should affect another one.
There should be only one collection of People. Now you have two in two different view models.

ContentControl not refreshing View when new ViewModel is created

I am trying to make an app using using MVVMLight that has a sidebar with buttons, each button shows a new usercontrol hosted in a ContentControl. When the user clicks the buttons in the sidebar (Show View1 / Show View2) it shows the views correctly.
My problems arise when the user has already shown a View (it could be View1 or View2 ), say View1 and click (Show View1) ** again ** View1 controls remain with the same values and I would like to show the same view with all controls as if it had restarted. (I know that I could reset all controls within the user control (View1) but my application requires having a new instance of the view every time the button is clicked).
Somehow, in the same scenario when the user is in View 1, switch to view 2 and return to view 1, a new instance is created and shown as I would like. I would like to get the same result without the need to switch to view 2 and return.
Here is a minimal reproducible example of the issue:
ViewModelLocator.cs
using CommonServiceLocator;
using GalaSoft.MvvmLight.Ioc;
namespace SidebarApp.ViewModel
{
public class ViewModelLocator
{
/// <summary>
/// Initializes a new instance of the ViewModelLocator class.
/// </summary>
public ViewModelLocator()
{
ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);
// Register viewmodels
SimpleIoc.Default.Register<MainViewModel>();
SimpleIoc.Default.Register<View1ViewModel>();
SimpleIoc.Default.Register<View2ViewModel>();
}
public MainViewModel Main { get { return ServiceLocator.Current.GetInstance<MainViewModel>(); } }
public View1ViewModel View1Vm { get { return ServiceLocator.Current.GetInstance<View1ViewModel>(); } }
public View2ViewModel View2Vm { get { return ServiceLocator.Current.GetInstance<View2ViewModel>(); } }
public static void Cleanup()
{
// TODO Clear the ViewModels
}
}
}
MainViewModel.cs
using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;
using System.Windows.Input;
namespace SidebarApp.ViewModel
{
public class MainViewModel : ViewModelBase
{
// Commands
public ICommand ShowView1Command { get; private set; }
public ICommand ShowView2Command { get; private set; }
/// <summary>
/// Property that will cointain the current viewmodel to show
/// ViewModelBase inplements ObservableObject class which imlements INotifyPropertyChanged
/// </summary>
public ViewModelBase CurrentViewModel { get; set; }
/// <summary>
/// Initializes a new instance of the MainViewModel class.
/// </summary>
public MainViewModel()
{
this.ShowView1Command = new RelayCommand(ShowView1);
this.ShowView2Command = new RelayCommand(ShowView2);
}
private void ShowView1()
{
// I tried this but it doesn't work
//CurrentViewModel = null or View2ViewModel;
CurrentViewModel = new View1ViewModel();
}
private void ShowView2()
{
CurrentViewModel = new View2ViewModel();
}
}
}
MainWindow.xaml
<Window x:Class="SidebarApp.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:SidebarApp"
mc:Ignorable="d"
DataContext="{Binding Main, Source={StaticResource Locator}}"
Title="MainWindow" Height="348.965" Width="560.683">
<Window.Resources>
<DataTemplate DataType="{x:Type local:View1ViewModel}">
<local:View1View />
</DataTemplate>
<DataTemplate DataType="{x:Type local:View2ViewModel}">
<local:View2View />
</DataTemplate>
</Window.Resources>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.3*"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<StackPanel>
<Button Command="{Binding ShowView1Command}">Show View1</Button>
<Button Command="{Binding ShowView2Command}">Show View2</Button>
</StackPanel>
<ContentControl Grid.Column="1" Content="{Binding Path=CurrentViewModel}"></ContentControl>
</Grid>
</Window>
View1View.xaml
<UserControl x:Class="SidebarApp.View1View"
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:local="clr-namespace:SidebarApp"
mc:Ignorable="d"
DataContext="{Binding View1Vm, Source={StaticResource Locator}}"
d:DesignHeight="450" d:DesignWidth="800">
<Grid Background="LightPink">
<StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
<TextBlock HorizontalAlignment="Center" Text="Welcome to View 1" FontSize="20"/>
<TextBox HorizontalAlignment="Stretch" Text="Original text value"/>
<CheckBox Content="Some boolean value"/>
</StackPanel>
</Grid>
</UserControl>
View1ViewModel.cs
using GalaSoft.MvvmLight;
namespace SidebarApp
{
public class View1ViewModel : ViewModelBase
{
public View1ViewModel()
{
}
}
}
View2View.xaml
<UserControl x:Class="SidebarApp.View2View"
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:local="clr-namespace:SidebarApp"
mc:Ignorable="d"
DataContext="{Binding View2Vm, Source={StaticResource Locator}}"
d:DesignHeight="450" d:DesignWidth="800">
<Grid Background="LightCyan">
<StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
<TextBlock HorizontalAlignment="Center" Text="Welcome to View 2" FontSize="20"/>
<TextBox HorizontalAlignment="Stretch" Text="Some text in view2"/>
<Button Content="Button"/>
</StackPanel>
</Grid>
</UserControl>
View2ViewModel.cs
using GalaSoft.MvvmLight;
namespace SidebarApp
{
public class View2ViewModel : ViewModelBase
{
public View2ViewModel()
{
}
}
}
App.xaml
<Application x:Class="SidebarApp.App" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:SidebarApp" StartupUri="MainWindow.xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" d1p1:Ignorable="d" xmlns:d1p1="http://schemas.openxmlformats.org/markup-compatibility/2006">
<Application.Resources>
<ResourceDictionary>
<vm:ViewModelLocator x:Key="Locator" d:IsDataSource="True" xmlns:vm="clr-namespace:SidebarApp.ViewModel" />
</ResourceDictionary>
</Application.Resources>
</Application>
For example I enter to the view1 and change the value of the textbox ("Original text value") to another value and I click again in Show View1 the text and everything in the usercontrol stays the same but when I switch to view2 and go back to view1 a new usercontrol is shown with his original values.

This might feel like something of a workaround, but it works. Hopefully it will prove useful. (Obviously make same changes to View2View view/view model).
ViewModelLocator.cs
public View1ViewModel View1Vm { get { return new View1ViewModel(); } }
MainViewViewModel.cs
private void ShowView1()
{
CurrentViewModel = new ViewModelLocator().View1Vm;
}
View1View.xaml
<UserControl x:Class="SidebarApp.View1View"
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:local="clr-namespace:SidebarApp"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800">
<Grid Background="LightPink">
<StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
<TextBlock HorizontalAlignment="Center" Text="Welcome to View 1" FontSize="20"/>
<TextBox HorizontalAlignment="Stretch" Text="{Binding Path=View1Text, Mode=TwoWay}"/>
<CheckBox Content="Some boolean value" IsChecked="{Binding Path=CheckBoxChecked, Mode=TwoWay}"/>
</StackPanel>
</Grid>
</UserControl>
View1ViewModel.cs
public class View1ViewModel : ViewModelBase
{
private string _view1Text;
private bool _checkBoxedChecked;
public string View1Text
{
get
{
return _view1Text;
}
set
{
_view1Text = value;
RaisePropertyChanged("View1Text");
}
}
public bool CheckBoxChecked
{
get
{
return _checkBoxedChecked;
}
set
{
_checkBoxedChecked = value;
RaisePropertyChanged("CheckBoxChecked");
}
}
public View1ViewModel()
{
View1Text = "Original text value";
}
}

WPF update textblock from different window

I have a window called RolledPaper.xaml with a textblock called SequenceValue.
SequenceValue is defined in another window called CounterSettings.xaml by typing in a textbox called SequenceRequested. I would like to have SequenceValue be always in sinch with SequenceRequested.
I tryed and failed using the same datacontext for both windows.
here it is the code for RolledPaper.xaml:
<Window x:Class="Numbering3.View.RolledPaper"
WindowStyle="None"
ResizeMode="NoResize"
BorderBrush="LightGray"
BorderThickness="5"
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:Numbering3.View"
xmlns:vm="clr-namespace:Numbering3.ViewModel"
xmlns:cv="clr-namespace:Numbering3.Helper"
xmlns:vo="clr-namespace:Numbering3.ViewModel"
xmlns:sys="clr-namespace:System;assembly=mscorlib"
mc:Ignorable="d"
Title="RolledPaper" Height="750" Width="1218"
Background="{DynamicResource WindowBrush}"
DataContextChanged="Rolledpaper_DataContextChanged">
<Window.DataContext>
<vm:ViewModelRolledPaper/>
</Window.DataContext>
<TextBlock x:Name="SequenceValue" Grid.Column="3" HorizontalAlignment="Left" Height="19" Margin="72,310,0,0" TextWrapping="Wrap"
Background="White" VerticalAlignment="Top" Width="98" Text="{Binding _SequenceValueToShow.SequenceValuetoShow, Mode=TwoWay, FallbackValue=NNN, TargetNullValue=NNN, UpdateSourceTrigger=PropertyChanged}"/>
</Grid>
code behind:
public partial class RolledPaper : Window
{
public RolledPaper()
{
WindowStartupLocation = System.Windows.WindowStartupLocation.CenterScreen;
SaveKeeper.fromMain = false;
InitializeComponent();
this.MouseLeftButtonDown += delegate { this.DragMove(); };
DataContextChanged += new DependencyPropertyChangedEventHandler(Rolledpaper_DataContextChanged);
}
the CounterSetting window:
<Window x:Class="Numbering3.View.CounterSettings"
...
...
<Window.DataContext>
<ViewModelCounterSettings/>
</Window.DataContext>
<Grid Margin="0,-19,-0.4,0">
<TextBox x:Name="SequenceRequested" PreviewTextInput="SequenceValidationTextBox" MaxLength="10" HorizontalAlignment="Left" Height="23" Margin="154,324,0,0" TextWrapping="Wrap"
Text="{Binding Path=_SequenceValueToShow.SequenceValueToKeep, FallbackValue='NNN', TargetNullValue ='NNN', Mode=TwoWay, UpdateSourceTrigger=PropertyChanged }" VerticalAlignment="Top" Width="120" TextChanged="SequenceRequested_TextChanged" />
</Grid>
its code behind:
public partial class CounterSettings : Window
{
public CounterSettings()
{
InitializeComponent();
this.MouseLeftButtonDown += delegate { this.DragMove(); };
DataContextChanged += new DependencyPropertyChangedEventHandler(CounterSettings_DataContextChanged);
}
And the SequeneValue class:
public class SequenceValue : INotifyPropertyChanged
{
public string SequenceValueToKeep
{
get
{
return _sequenceValueToKeep=_sequenceProcessor.GetSequence();
}
set
{
if (_sequenceValueToKeep != value)
{
__sequenceValueToKeep = value;
RaisePropertyChanged("SequenceValueToKeep");
}
}
}
private void RaisePropertyChanged(string prop)
{
if (PropertyChanged != null)
{ PropertyChanged(this, new PropertyChangedEventArgs(prop)); }
}
public event PropertyChangedEventHandler PropertyChanged;
}
}
I need to put a value in the textbox of countersetting =>string Sequencevalue.SequenceValueToKeep is updated => textblock in RolledPaper window shows Sequencevalue.SequenceValueToKeep .
Thank you.

Solutio 1:
You can use one Static ViewModel to get the to to know each other.
in App.xaml
<Application.Resources>
...
<MainViewModel x:Key="mainViewModel" />
</Application.Resources>
and then in CounterSetting.xaml
<Window otherProperties=...
DataContext="{Binding ViewModelCounterSettings, Source={StaticResource mainViewModel}}"/>
and in RolledPaper.xaml
<Window otherProperties=...
DataContext="{Binding ViewModelRolledPaper, Source={StaticResource mainViewModel}}"/>
The MainViewModel does inits your two ViewModel and makes them accessible as properties and also gives the the same instance of SequenceValue
Solution 2:
Create an object of SequenceValue as an static resource, like
<Application.Resources>
...
<SequenceValue x:Key="sequenceValue"/>
</Application.Resources>
and set it as the DataContext of your TextBox and TextBlock
<TextBox DataContext="{StaticResource sequenceValue}"
Text="{Binding SequenceValueToKeep, FallbackValue='NNN', TargetNullValue='NNN', Mode=TwoWay, UpdateSourceTrigger=PropertyChanged }"
... />
<TextBlock DataContext="{StaticResource sequenceValue}"
Text="{Binding SequenceValuetoShow, FallbackValue=NNN, TargetNullValue=NNN, UpdateSourceTrigger=PropertyChanged}"

Data binding to the output of a method

I'm trying to display the output of a method in a WPF TextBox. I'm just trying a simple attempt, to print a single string 3 in a TextBox.
I'm trying to do it the following way, using an ObjectDataProvider:
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication1"
xmlns:system="clr-namespace:System;assembly=mscorlib"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<ObjectDataProvider x:Key="dataprovider" ObjectType="{x:Type system:String}" MethodName="GetValue">
</ObjectDataProvider>
</Window.Resources>
<Grid>
<TextBox Text="{Binding Source={StaticResource dataprovider}, Mode=OneWay}" HorizontalAlignment="Left" Height="23" Margin="201,168,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
</Grid>
</Window>
And here's my code behind:
namespace WpfApplication1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
public string GetValue()
{
return "3";
}
}
}
I'm getting no output. the TextBox is just blank. Where am I going wrong?

Instead of ObjectDataProvider create a property like this:
public string GetMethod
{
get
{
return GetValue();
}
}
And:
public MainWindow()
{
InitializeComponent();
DataContext = this;
}
Then in the XAML remove ObjectDataProvider and just:
<TextBox Text="{Binding GetMethod, Mode=OneWay}" HorizontalAlignment="Left"
Height="23" Margin="201,168,0,0" TextWrapping="Wrap"
VerticalAlignment="Top" Width="120"/>

Why doesn't TextBlock bind?

When I run this simple wpf app, I get a blank window. Any ideas what I'm doing wrong?
//MainWindow.xaml.cs
public string SimpleText {get;set;}
public MainWindow()
{
InitializeComponent();
SimpleText = "this is a test";
}
//MainWindow.xaml
<StackPanel>
<TextBlock Text="{Binding SimpleText}" Width="200"/>
</StackPanel>

DataContext is a way to go but you can also use RelativeSource markup extension to get window's property:
<TextBlock Text="{Binding SimpleText, RelativeSource={RelativeSource
Mode=FindAncestor, AncestorType=Window}}" Width="200"/>

You must set the DataContext:
public MainWindow()
{
InitializeComponent();
SimpleText = "this is a test";
this.DataContext = this;
}
As an alternative, you can set DataContext on the side XAML like this:
XAML
<Window x:Class="TextBlockDontBind.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:this="clr-namespace:TextBlockDontBind"
Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
<this:TestData />
</Window.DataContext>
<StackPanel>
<TextBlock Text="{Binding SimpleText}" Width="200"/>
</StackPanel>
</Window>
Code-behind
public class TestData
{
private string _simpleText = "this is a test";
public string SimpleText
{
get
{
return _simpleText;
}
set
{
_simpleText = value;
}
}
}
But in this case to update a property, for a Class must implement the INotifyPropertyChanged interface.

Develop Reference

C# (C-Sharp) is a programming language developed by Microsoft that runs on the .NET Framework.

Wpf Databinding with ViewModel as property - c#

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WPF update textblock from different window

Data binding to the output of a method

Why doesn't TextBlock bind?

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