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Dynamic ViewModel's bound values becomes null in WPF

I followed few online tutorials to switch between dynamic views from a ListView.
In my MainWindow, I have a ListView in the left pane with ItemsSource of list of sub ViewModels. (Each sub ViewModel implements an Interface)
Each ViewModel have its own View as a DataTemplate.
I'm calling the GenerateReport() method of the selected view from the MainWindow. But the values of selected views becomes null.
Download my source from Github.
Steps to reproduce the issue:
Run the application and type text in the Students Report's Id and Name. (The breakpoints in StudentReportViewModels's properties are properly hitting and values updated.)
Then click Generate Report button. The StudentReportViewModels's properties values becomes null.
How to fix the issue? Please help.
Source:
MainWindow.xaml
<Window.Resources>
<DataTemplate DataType="{x:Type vm:StudentsReportViewModel}">
<view:StudentsReport/>
</DataTemplate>
<DataTemplate DataType="{x:Type vm:MarksReportViewModel}">
<view:MarksReport />
</DataTemplate>
</Window.Resources>
<Window.DataContext>
<local:MainWindowViewModel/>
</Window.DataContext>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="200"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<ListView ItemsSource="{Binding Reports}" SelectedItem="{Binding SelectedReport, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}"/>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<GridSplitter Grid.Row="1" Grid.Column="1" Width="5" ResizeBehavior="PreviousAndNext" HorizontalAlignment="Stretch"/>
<Grid Grid.Column="2">
<Grid.RowDefinitions>
<RowDefinition Height="2*"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<ScrollViewer Grid.Row="0" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto">
<ContentControl Content="{Binding SelectedReport.ViewModel, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</ScrollViewer>
<Button Content="Generate Report" Grid.Row="2" Margin="5" HorizontalAlignment="Right" Command="{Binding GenerateReportCommand}"/>
</Grid>
</Grid>
MainWindowViewModel:
public class MainWindowViewModel : INotifyPropertyChanged
{
private ICommand _generateReportCommand;
private Report selectedReport;
public Report SelectedReport
{
get
{
return this.selectedReport;
}
set
{
if (value != this.selectedReport)
{
this.selectedReport = value;
NotifyPropertyChanged();
}
}
}
public List<Report> Reports { get; set; }
public ICommand GenerateReportCommand
{
get
{
if (_generateReportCommand == null)
{
_generateReportCommand = new RelayCommand(
p => GenerateReport()
);
}
return _generateReportCommand;
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public MainWindowViewModel()
{
Reports = new List<Report>
{
new Report{ Name = "Students Report", ViewModel = new StudentsReportViewModel()},
new Report{ Name = "Marks Report", ViewModel = new MarksReportViewModel()}
};
SelectedReport = Reports[0];
}
public void GenerateReport()
{
SelectedReport.ViewModel.GenerateReport();
}
}
StudentsReport.xaml
<TextBox Height="25" Width="100" Margin="5" Text="{Binding Id, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
<TextBox Height="25" Width="100" Margin="5" Text="{Binding Name, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
StudentsReportViewModel:
public class StudentsReportViewModel : INotifyPropertyChanged, IReportViewModel
{
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
private string id;
public string Id
{
get
{
return this.id;
}
set
{
if (value != this.id)
{
this.id = value;
NotifyPropertyChanged();
}
}
}
private string name;
public string Name
{
get
{
return this.name;
}
set
{
if (value != this.name)
{
this.name = value;
NotifyPropertyChanged();
}
}
}
public StudentsReportViewModel()
{
}
public void GenerateReport()
{
System.Windows.MessageBox.Show($"Id = {Id}, Name = {Name}");
}
}
Interface:
public interface IReportViewModel
{
void GenerateReport();
}
Model:
public class Report
{
public string Name { get; set; }
public IReportViewModel ViewModel { get; set; }
}

Your StudentsReport.xaml UserControl is binding to an instance of the StudentsReportViewModel created in the XAML:
<UserControl.DataContext>
<vm:StudentsReportViewModel/>
</UserControl.DataContext>
The Generate Report button however is calling into another instance of the StudentsReportViewModel that is create in the MainWindowVieModel constructor and is stored in the Report class.
Reports = new List<Report>
{
new Report{ Name = "Students Report", ViewModel = new StudentsReportViewModel()},
new Report{ Name = "Marks Report", ViewModel = new MarksReportViewModel()}
};
You need to remove one of these instances so that the UserControl's DataContext is bound to the same view model instance that you are generating the report message from.
I suggest deleting this code from StudentsReport.xaml:
<UserControl.DataContext>
<vm:StudentsReportViewModel/>
</UserControl.DataContext>

Binding multiple WPF user defined combo boxes to same single Observable collection

In my code I have one observable collection that has many combo boxes inside that. Now I have to add List for each combo boxes using MVVM (Model-View-View Model) i.e., No code behind
In View.xaml:
<Window.... xmlns:VM="clr-namespace:myproject.myViewModel"
... >
<Window.DataContext><VM:myViewModel/>
</Window.DataContext>
<ItemsControl ItemsSource="{Binding myCollection}" >
<ItemsControl.ItemTemplate >
<DataTemplate>
<DockPanel>
<Grid >
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid Margin="0,20,0,0" >
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBlock Text="City" Margin="20" VerticalAlignment="Center"/>
<ComboBox KeyboardNavigation.TabIndex="0" Grid.Column="1" Margin="45,10,10,10" Height="30" Width="200" ItemsSource="{Binding City}" />
<TextBlock Text="temperature" Grid.Row="1" VerticalAlignment="Center" Margin="20" />
<ComboBox KeyboardNavigation.TabIndex="3" Grid.Column="1" Grid.Row="1" Margin="45,20,10,10" Height="30" Width="200" SelectedIndex="0" HorizontalContentAlignment="Right"
VerticalAlignment="Center" ItemsSource="{Binding Temperature}">
</ComboBox>
<TextBlock Text="State" Grid.Row="1" VerticalAlignment="Center" Margin="10" Grid.Column="2"/>
<ComboBox KeyboardNavigation.TabIndex="3" Grid.Column="3" Grid.Row="1" Margin="10" Height="30" Width="200" HorizontalContentAlignment="Center" ItemsSource="{Binding State}" >
</ComboBox>
<TextBlock Text="Open Files " VerticalAlignment="Center" Grid.Row="0" Grid.Column="2" Margin="10" />
<TextBox Grid.Column="3" Text="" Height="30" Grid.Row="0" IsReadOnly="True"
TextAlignment="Right" VerticalContentAlignment="Center" Width="200" /> <Button Grid.Column="4" Content="Browse" Height="30" VerticalAlignment="Bottom" MinWidth="41" />
</Grid>
</Window>
In **Model.cs**:
namespace myproject.Models
{
public class projectmodel : INotifyPropertyChanged
{
private ObservableCollection<projectmodel> city;
private ObservableCollection<projectmodel> temperature;
private ObservableCollection<projectmodel> state;
public ObservableCollection<projectmodel> City
{
get { return city; }
set
{
city = value;
NotifyPropertyChanged("City");
}
}
public ObservableCollection<projectmodel> Temperature
{
get { return temperature; }
set
{
temperature = value;
NotifyPropertyChanged("Temperature");
}
}
public ObservableCollection<projectmodel> State
{
get { return state; }
set
{
state = value;
NotifyPropertyChanged("State");
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
#endregion
#region Private Helpers
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
}}
In ViewModel.cs:
namespace myproject.ViewModels
{
public class projectViewModel
{
public ObservableCollection<T> myCollection
{
get; set;
}
public projectViewModel()
{
myCollection = new ObservableCollection<T>();
List<string> lstCity = new List<string>();
lstCity = new List<string> { "Coimbatore", "Chennai", "Bangalore" };
List<string> lstTemperature = new List<string>();
lstTemperature = new List<string> { "17c", "18c", "15c" };
List<string> lstState = new List<string>();
lstState = new List<string> { "Andhra", "karnataka", "TamilNadu" };
}
}myCollection.Add(new projectmodel
{
City = lstCity.ToArray(),
Temperature = lstTemperature.ToArray(),
State= lstState.ToArray()
});
}
}}
This is my code,I didn't get anything if I select my combo boxes. Please suggest me how should I write my viewmodel.cs ,and also correct me if I'm wrong anywhere else.

You have to declare all your collections inside your projectmodel to be of type ObservableCollection<string> instead of sting[]. When ever you bind to a collection use ObservableCollection<T>.
Your view models must also all implement INotifyPropertyChanged
Changes:
ProjectModel:
namespace Myproject.Models
{
public class ProjectModel : INotifyPropertyChanged
{
private ObservableCollection<string> city;
private ObservableCollection<string> temperature;
private ObservableCollection<string> state;
public ObservableCollection<string> City
{
get { return city; }
set
{
city = value;
NotifyPropertyChanged("City");
}
}
public ObservableCollection<string> Temperature
{
get { return temperature; }
set
{
temperature = value;
NotifyPropertyChanged("Temperature");
}
}
public ObservableCollection<string> State
{
get { return state; }
set
{
state = value;
NotifyPropertyChanged("State");
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
#endregion
#region Private Helpers
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
}
}
ProjectViewModel:
namespace MyProject.ViewModels
{
public class ProjectViewModel : INotifyPropertyChanged
{
private ObservableCollection<Projectmodel> myCollection;
public ObservableCollection<Projectmodel> MyCollection
{
get => this.myCollection;
set
{
if (Equals(value, this.myCollection)) return;
this.myCollection = value;
OnPropertyChanged();
}
}
public ProjectViewModel()
{
MyCollection = new ObservableCollection<Projectmodel>()
{
new ProjectModel()
{
City = new ObservableCollection<string>()
{
"Coimbatore", "Chennai", "Bangalore"
},
Temperature = new ObservableCollection<string>()
{
"17c", "18c", "15c"
},
State = new ObservableCollection<string>()
{
"Andhra", "karnataka", "TamilNadu"
}
}
};
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Edit:
I updated the code to meet the common naming conventions using PascalCase. It is recommended to follow them: C# Conventions

Save Changes of View in Viewmodel?

I'm trying to display a model and I want to save it when the user clicks a button.
(Bind ModelView OneWay to Model and if the save button was pressed I update the source manually.)
Is that possible?
Here I created a small example with my problem. (not MVVM!)
MainWindow.xaml
<Grid>
<Grid.DataContext>
<ViewModel:MainViewModel/>
</Grid.DataContext>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<local:PersonListView Grid.Column="0" DataContext="{Binding ViewModel_PersonList}"/>
<local:PersonView Grid.Column="1" DataContext="{Binding ViewModel_Person}"/>
</Grid>
PersonListView.xaml
<ListView ItemsSource="{Binding PersonList}" SelectedItem="{Binding SelectedPerson}">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding LastName}"/>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
PersonView.xaml
<Grid DataContext="{Binding}">
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="auto"/>
<RowDefinition Height="auto"/>
<RowDefinition Height="auto"/>
<RowDefinition/>
<RowDefinition Height="auto"/>
</Grid.RowDefinitions>
<TextBlock Text="First Name:" Grid.Column="0" Grid.Row="0" Margin="5"/>
<TextBlock Text="Last Name:" Grid.Column="0" Grid.Row="1" Margin="5"/>
<TextBlock Text="Age:" Grid.Column="0" Grid.Row="2" Margin="5"/>
<TextBox Text="{Binding Path=Person.FirstName, UpdateSourceTrigger=Explicit}" Grid.Column="1" Grid.Row="0" Margin="5"/>
<TextBox Text="{Binding Path=Person.LastName, UpdateSourceTrigger=Explicit}" Grid.Column="1" Grid.Row="1" Margin="5"/>
<TextBox Text="{Binding Path=Person.Age, UpdateSourceTrigger=Explicit}" Grid.Column="1" Grid.Row="2" Margin="5"/>
<Button Content="Save" Command="{Binding SaveCommand}" Grid.Column="1" Grid.Row="4"/>
</Grid>
Person.cs
public class Person : INotifyPropertyChanged
{
private string firstName;
public string FirstName
{
get { return firstName; }
set
{
firstName = value;
OnPropertyChanged("FirstName");
}
}
private string lastName;
public string LastName
{
get { return lastName; }
set
{
lastName = value;
OnPropertyChanged("LastName");
}
}
private int age;
public int Age
{
get { return age; }
set
{
age = value;
OnPropertyChanged("Age");
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
MainViewModel.cs
public class MainViewModel : ViewModelBase
{
/// <summary>
/// Initializes a new instance of the MainViewModel class.
/// </summary>
public MainViewModel()
{
ViewModel_PersonList.PersonList.Add(new Model.Person()
{
LastName = "Test",
FirstName = "John",
Age = 20
});
ViewModel_PersonList.PersonList.Add(new Model.Person()
{
LastName = "Example",
FirstName = "Luke",
Age = 25
});
ViewModel_PersonList.SelectedPerson = ViewModel_PersonList.PersonList[1];
ViewModel_Person.Person = ViewModel_PersonList.SelectedPerson;
}
ViewModel.PersonViewModel _ViewModel_Person = new ViewModel.PersonViewModel();
public ViewModel.PersonViewModel ViewModel_Person
{
get
{
return _ViewModel_Person;
}
set
{
_ViewModel_Person = value;
RaisePropertyChanged("ViewModel_Person");
}
}
ViewModel.PersonListViewModel _ViewModel_PersonList = new ViewModel.PersonListViewModel();
public ViewModel.PersonListViewModel ViewModel_PersonList
{
get
{
return _ViewModel_PersonList;
}
set
{
_ViewModel_PersonList = value;
RaisePropertyChanged("ViewModel_PersonList");
}
}
}
PersonListViewModel.css
public class PersonListViewModel : ViewModelBase
{
ObservableCollection<Model.Person> _PersonList = new ObservableCollection<Model.Person>();
public ObservableCollection<Model.Person> PersonList
{
get
{
return _PersonList;
}
set
{
_PersonList = value;
RaisePropertyChanged("PersonList");
}
}
Model.Person _SelectedPerson = new Model.Person();
public Model.Person SelectedPerson
{
get
{
return _SelectedPerson;
}
set
{
MessengerInstance.Send<Model.Person>(value);
_SelectedPerson = value;
RaisePropertyChanged("SelectedPerson");
}
}
}
PersonViewModel.cs
public class PersonViewModel : ViewModelBase
{
public PersonViewModel()
{
MessengerInstance.Register<Model.Person>(this, per => Person = per);
}
Model.Person _Person = new Model.Person();
public Model.Person Person
{
get
{
return _Person;
}
set
{
_Person = value;
RaisePropertyChanged("Person");
}
}
private RelayCommand<Model.Person> _SaveCommand;
public ICommand SaveCommand
{
get
{
if (_SaveCommand == null)
_SaveCommand = new RelayCommand<Model.Person>(SaveCommand_Execute, SaveCommand_CanExecute);
return _SaveCommand;
}
}
private bool SaveCommand_CanExecute(Model.Person newPerson)
{
return true;
}
private void SaveCommand_Execute(Model.Person newPerson)
{
// Do my saving!
}
}
Thank you!

You can make the Mode=TwoWay and use UpdateSourceTrigger=Explicit. Refer below code.
<StackPanel>
<TextBox Name="tb_1" Text="HelloWorld!"/>
<TextBox Name="tb_2" Text="{Binding Path=Text, ElementName=tb_1, Mode=TwoWay,UpdateSourceTrigger=Explicit}"/>
<Button Content="Update Source" Click="Button_Click"/>
</StackPanel>

Getting Values displayed in one method call XAML WPF

As the title says, im trying to display the hardcoded values I typed in my XAML file through databindings but in 1 method call instead of binding the textboxes in every specific property.
Model:
public class Person
{
public string Namn { get; set; }
public DateTime Födelsedatum { get; set; }
public int Betyg { get; set; }
public int AntalBarn { get; set; }
public int Favoritsiffra { get; set; }
public string Kommentar { get; set; }
}
View:
<Window x:Class="PiedPiper.View.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Inlämningsuppgift WPF" Height="400" Width="400">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Label Content="Personuppgifter" FontSize="35" Grid.Column="0" Grid.Row="0"></Label>
<Separator Grid.Column="0" Grid.Row="1" Grid.ColumnSpan="2" Margin="10,2,-50,2"/>
<Label Content="Namn:" Grid.Column="0" Grid.Row="2" Margin="5,5,210,0"></Label>
<TextBox Name="NamnTextBox" Grid.Row="2" Grid.Column="0" Grid.ColumnSpan="2" Margin="118,5,-50,0"/>
<Label Content="Födelsedatum:" Grid.Column="0" Grid.Row="3" Margin="5,5,210,0"></Label>
<TextBox Name="FödelsedatumTextBox" Grid.Row="3" Grid.Column="0" Grid.ColumnSpan="2" Margin="118,5,-50,0"></TextBox>
<Label Content="Betyg" Grid.Column="0" Grid.Row="4" Margin="5,5,210,0"></Label>
<ComboBox Name="BetygComboBox" Grid.Row="4" Grid.Column="0" Grid.ColumnSpan="2" Margin="218,5,-50,0"></ComboBox>
<Label Content="Antal barn (0-20):" Grid.Column="0" Grid.Row="5" Margin="5,5,210,0"></Label>
<Slider Grid.Row="5" Grid.Column="0" Grid.ColumnSpan="2" Margin="125,5,25,0"></Slider>
<TextBox Name="AntalBarnTextBox" Grid.Row="5" Grid.Column="0" Grid.ColumnSpan="2" Margin="300,5,-50,0"></TextBox>
<Label Content="Favoritsiffra (0-99):" Grid.Column="0" Grid.Row="6" Margin="5,5,210,0"></Label>
<TextBox Name="FavoritsiffraTextBox" Grid.Row="6" Grid.Column="0" Grid.ColumnSpan="2" Margin="225,5,-50,0"></TextBox>
<CheckBox Content="Visa kommentar" Grid.Row="7" Grid.Column="0" Margin="5,5,210,0"></CheckBox>
<TextBox Name="KommentarTextBox" Grid.Row="7" Grid.Column="0" Grid.ColumnSpan="2" Margin="125,5,-50,-50" Grid.RowSpan="2"></TextBox>
<Button Content="Spara" Grid.Row="8" Grid.Column="0" Margin="125,55,-50,-80" Grid.ColumnSpan="2"></Button>
<Separator Grid.Row="9" Grid.Column="0" Grid.ColumnSpan="2" Margin="10,85,-50,-80"></Separator>
<Label Content="Andre Kordasti" Grid.Row="10" Grid.Column="0" Margin="10,85,-50,-80"></Label>
<Button Content="Avsluta" Grid.Row="10" Grid.Column="0" Margin="225,85,-50,-80" Grid.ColumnSpan="2"></Button>
</Grid>
ViewModel:
public class PersonViewModel : INotifyPropertyChanged
{
public PersonViewModel(Person person)
{
Namn = person.Namn;
Födelsedatum = person.Födelsedatum;
Betyg = person.Betyg;
AntalBarn = person.AntalBarn;
Favoritsiffra = person.Favoritsiffra;
Kommentar = person.Kommentar;
GetPerson();
}
private void GetPerson()
{
Namn = "KurtSune";
Födelsedatum = new DateTime(1980, 09, 06);
Betyg = 3;
AntalBarn = 7;
Favoritsiffra = 10;
Kommentar = "Kommentar...";
var mainWindow = new MainWindow();
mainWindow.NamnTextBox.Text = Namn;
mainWindow.FödelsedatumTextBox.Text = Convert.ToString(Födelsedatum);
mainWindow.BetygComboBox.SelectedValue = Betyg;
mainWindow.AntalBarnTextBox.Text = Convert.ToString(AntalBarn);
mainWindow.FavoritsiffraTextBox.Text = Convert.ToString(Favoritsiffra);
mainWindow.KommentarTextBox.Text = Kommentar;
}
public ICommand SaveCommand { get; set; }
public ICommand AbortCommand { get; set; }
public bool CanSave
{
get
{
if (Namn == null)
{
return false;
}
return !String.IsNullOrWhiteSpace(Namn);
}
}
private string _namn;
public string Namn
{
get { return _namn; }
set { _namn = value; OnPropertyChanged("Namn"); }
}
private DateTime _födelsedatum;
public DateTime Födelsedatum
{
get { return _födelsedatum; }
set { _födelsedatum = value; OnPropertyChanged("Födelsedatum"); }
}
private int _betyg;
public int Betyg
{
get { return _betyg; }
set { _betyg = value; OnPropertyChanged("Betyg"); }
}
private int _antalBarn;
public int AntalBarn
{
get { return _antalBarn; }
set { _antalBarn = value; OnPropertyChanged("AntalBarn"); }
}
private int _favoritSiffra;
public int Favoritsiffra
{
get { return _favoritSiffra; }
set { _favoritSiffra = value; OnPropertyChanged("Födelsedatum"); }
}
private string _kommentar;
public string Kommentar
{
get { return _kommentar; }
set { _kommentar = value; OnPropertyChanged("Kommentar"); }
}
private void OnPropertyChanged(string propertyName)
{
var handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
}
And to add my App.xaml.cs file:
public partial class App : Application
{
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
var person = new Person();
var personViewModel = new PersonViewModel(person);
var mainWindow = new MainWindow();
mainWindow.DataContext = personViewModel;
mainWindow.Show();
}
}
So I dont get the following values to be displayed... Please help, Iam new to this.

Here is a simplified example where,
I made a DataTemplate where controls are bound to the Person properties. Benefits are obvious because as you will see whichever end is modified, the other will know/show these changes.
(added a button and a MessageBox to further demonstrate this)
Code:
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows;
namespace WpfApplication1
{
public partial class MainWindow
{
public MainWindow()
{
InitializeComponent();
var person = new Person {Name = "name1", Address = "address1"};
person.PropertyChanged += person_PropertyChanged;
DataContext = person;
}
private void person_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
MessageBox.Show("data changed");
}
private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
{
var dataContext = (Person) DataContext;
dataContext.Name = "newName";
dataContext.Address = "newAddress";
}
}
internal class Person : INotifyPropertyChanged
{
private string _address;
private string _name;
public string Name
{
get { return _name; }
set
{
_name = value;
OnPropertyChanged();
}
}
public string Address
{
get { return _address; }
set
{
_address = value;
OnPropertyChanged();
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
XAML:
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:wpfApplication1="clr-namespace:WpfApplication1"
Title="MainWindow"
Width="525"
Height="350">
<Window.Resources>
<DataTemplate x:Key="PersonTemplate" DataType="wpfApplication1:Person">
<StackPanel>
<TextBlock Text="Name" />
<TextBox Text="{Binding Name, UpdateSourceTrigger=PropertyChanged}" />
<TextBlock Text="Address" />
<TextBox Text="{Binding Address, UpdateSourceTrigger=PropertyChanged}" />
</StackPanel>
</DataTemplate>
</Window.Resources>
<Grid>
<StackPanel>
<Button Click="ButtonBase_OnClick" Content="Modify" />
<ContentControl Content="{Binding}" ContentTemplate="{StaticResource PersonTemplate}" />
</StackPanel>
</Grid>
</Window>
Now as you can see there are no hard-coded values in XAML, the object I have passed to DataContext has sample values instead.

Failing To Bind Dynamically Generated Buttons & Textboxes in WPF

I was working on dynamic generation of labels, buttons and Textbox in my WPF application. Well I was successful in dynamically creating them but I am facing one major issue in it.
Xaml:
<ListBox x:Name="myViewChannelList" HorizontalAlignment="Stretch" Height="Auto" ItemsSource="{Binding}" Margin="0" VerticalAlignment="Stretch" Width="Auto">
<ListBox.ItemTemplate>
<DataTemplate >
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="170" />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Label Grid.Column="0" Content="{Binding Path=ChanelName}" Margin="50,20,0,0"></Label>
<Grid Grid.Column="1">
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<TextBox Grid.Column="0" Text="{Binding Path=VoltageText}" Height="25" Width="50" HorizontalAlignment="Center" VerticalAlignment="Center" Margin="0,0,0,0" />
<Button Grid.Column="1" Content="Set" Height="25" Command="{Binding ElementName=myViewChannelList, Path=DataContext.SetCommand}" Width="50" HorizontalAlignment="Center" VerticalAlignment="Center" Margin="0,0,0,0" ></Button>
</Grid>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Model Class:
private string _ChanelName = "";
public String ChanelName
{
get
{
return _ChanelName;
}
set
{
if (value != _ChanelName)
{
_ChanelName = value;
OnPropertyChanged("ChanelName");
}
}
}
// Constructor
public VoltageModel(string ChanelName)
{
this.ChanelName = ChanelName;
}
public override string ToString()
{
return _ChanelName;
}
ViewModel Class:
class ChannelList : ObservableCollection<VoltageModel>, INotifyPropertyChanged
{
private string _VoltageText;
public string VoltageText
{
get { return _VoltageText; }
set
{
_VoltageText = value;
OnPropertyChanged("VoltageText");
}
}
// Method gets called when Set Button Is Clicked
public void SetCommandExecuted()
{
string val = VoltageText;
}
//Notify Property Changed members are present
}
Xaml.cs Class:
ChannelList myChanels = new ChannelList();
public VoltageView() // Constructor
{
InitializeComponent();
myChanels.Add(new VoltageModel("VDD__Main"));
myChanels.Add(new VoltageModel("VDD__IO__AUD"));
myChanels.Add(new VoltageModel("VDD__CODEC__AUD"));
myViewChannelList.DataContext = myChanels;
}
This gives me 3 Labels(Content as above), 3 textboxes and 3 buttons when I run the application.
Now when I enter the value inside the textbox it shows null on button click when I put a breakpoint in SetCommandExecuted(). Most importantly any of the 4 button I click generates the event. I want the first textbox and first button to be in sync(bind), 2nd textbx and 2nd button to be in sync and so on. Basically each control must be in sync with the other control in a row. It should not effect the other rows. Is it possible???

Here is the solution to your question. As general practice you want to avoid all logic, building your data, etc. in the code behind. All the business logic should be in the view model which will make it easier to unit test.
Here is the view
.xaml
<StackPanel>
<ListBox HorizontalAlignment="Stretch"
Height="Auto"
ItemsSource="{Binding VoltageCollection}"
VerticalAlignment="Stretch"
Width="Auto">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<Label Width="100"
Content="{Binding ChannelName}" />
<TextBox Width="100"
Text="{Binding VoltageText}" />
<Button Margin="10,0,0,0"
Content="Set"
Command="{Binding VoltageCommand}"
CommandParameter="{Binding VoltageText}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</StackPanel>
Here is the code behind
.xaml.cs
private ChannelListViewModel m_voltageViewModel;
public MainWindow()
{
InitializeComponent();
m_voltageViewModel = new ChannelListViewModel();
m_voltageViewModel.Initialize();
DataContext = m_voltageViewModel;
}
Here is the Model: VoltageModel
public class VoltageModel : INotifyPropertyChanged
{
public string ChannelName { get; set; }
private string m_voltageText;
public string VoltageText
{
get { return m_voltageText; }
set
{
m_voltageText = value;
OnPropertyChanged("VoltageText");
}
}
public ICommand VoltageCommand { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Here is the ViewModel: ChannelListViewModel
public class ChannelListViewModel
{
private ICommand m_voltageCommand;
public ChannelListViewModel()
{
m_voltageCommand = new DelegateCommand(x => SetCommandExecute(x));
}
public void Initialize()
{
VoltageCollection = new ObservableCollection<VoltageModel> { new VoltageModel() { ChannelName = "VDD__Main", VoltageText = String.Empty, VoltageCommand = m_voltageCommand },
new VoltageModel() { ChannelName = "VDD__IO__AUD", VoltageText = String.Empty, VoltageCommand = m_voltageCommand },
new VoltageModel() { ChannelName = "VDD__CODEC__AUD", VoltageText = String.Empty, VoltageCommand = m_voltageCommand }};
}
public ObservableCollection<VoltageModel> VoltageCollection { get; set; }
public void SetCommandExecute(object voltageText)
{
Debug.WriteLine(voltageText);
}
}
Finally simple DelegateCommand class DelegateCommand
public class DelegateCommand : ICommand
{
Action<object> m_executeDelegate;
public DelegateCommand(Action<object> executeDelegate)
{
m_executeDelegate = executeDelegate;
}
public void Execute(object parameter)
{
m_executeDelegate(parameter);
}
public bool CanExecute(object parameter) { return true; }
public event EventHandler CanExecuteChanged;
}

i didn't get much into what was wrong since i recognized 2 things that were generally very wrong ,and they might be the problem for unexpected behavior on your part .
the first : your DataTemplate places your control one on top of the other .
fix :
<DataTemplate >
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Label Grid.Column="0" Content="{Binding Path=ChanelName}" />
<TextBox Grid.Column="1" Text="{Binding Path=VoltageText}" />
<Button Grid.Column="2" Command="{Binding ElementName=myViewChannelList, Path=DataContext.SetCommand}" />
</Grid>
</DataTemplate>
the second : your Properties are set after PropertyChanged event was risen so they would not be updated until the next time you input a value.
fix :
private T _property;
public T Property
{
get { return _property; }
set
{
_property = value;
OnPropertyChanged("Property");
}
}
make these fixes and edit your post if you still have issues post a comment under my answer.