How do I get the text bound to txtMessage from the second view model? When I had only one view model, the text was working fine. It does not work anymore when I moved the actual download code to second view model. Am I missing something? Any help appreciated.
Xaml:
<DockPanel DockPanel.Dock="Top">
<TextBlock x:Name="txtMessage" DockPanel.Dock="Top" Margin="5" Text="{Binding viewModel1.Message}" />
<StackPanel DockPanel.Dock="Top" Orientation="Horizontal" Margin="5,5">
<ProgressBar Width="300" Visibility="{Binding IsDownloading, Converter={converter:VisibilityConverter}}" IsIndeterminate="True" />
<Button Content="Cancel" />
</StackPanel>
</DockPanel>
<Button Content="Download" Width="120" Margin="0,0,5,0" Name="btnSubmit" Click="btnSubmit_Click" />
CodeBehind:
public partial class DownloadWindow: Window
{
DownloadWindowViewModel viewModel = new DownloadWindowViewModel();
public DownloadWindow()
{
InitializeComponent();
this.DataContext = viewModel;
}
private void btnSubmit_Click(object sender, RoutedEventArgs e)
{
viewModel.IsDownloading = true;
viewModel.Download();
}
}
viewModel:
public class DownloadWindowViewModel: INotifyPropertyChanged
{
Thread downloadThread;
public DownloadViewModel viewModel1;
public DownloadWindowViewModel()
{
viewModel1 = new DownloadViewModel();
}
private bool _isDownloading; = false;
public bool IsDownloading
{
get
{
return _isDownloading;
}
set
{
_isDownloading; = value;
OnPropertyChanged("IsDownloading");
}
}
public void Download()
{
viewModel1.Download();
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
viewModel1:
public class DownloadViewModel: INotifyPropertyChanged
{
Thread _thread;
public void Download()
{
ThreadStart threadStart = delegate()
{
StartDownload();
};
_thread = new Thread(threadStart);
_thread.IsBackground = true;
_thread.Start();
}
private void StartDownload()
{
for (int i = 10; i < 1500; i++)
{
Thread.Sleep(5000);
Message = "Downloading " + i.ToString();
}
}
private string _message = "";
public string Message
{
get
{
return _message;
}
set
{
if (_message != value)
{
_message = value;
OnPropertyChanged("Message");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Your viewModel1 has to be a property, and it's a field at the moment. Change it to:
public DownloadViewModel viewModel1 { get; set; }
Explanation why such restriction exists, can be found here (primarily due to notification/verifications mechanisms simply not working for fields):
Why does WPF support binding to properties of an object, but not fields?
Related
I have the following textbox
<TextBox Grid.Column="1"
Grid.Row="1"
Name="groupAddressBox"
Width ="80"
Text="{Binding Path=GroupAddress, Converter={StaticResource groupAddressConverter}}"/>
When I change the text manually, it's all good.
But when I try to do this via a button
private void Test_Click(object sender, RoutedEventArgs e)
{
groupAddressBox.Text = "0/0/1";
}
Although the text changes, the source is not updated, and when I click on ok, it recognizes the value that was there before the change.
I cannot upgrade the source straight away, so I prefer to do this this way.
Is there something that can help me force the source upgrade via this way?
Based on your question, I tried to create a Simple Example of MVVM Pattern with very basic functionality. Please do necessary change to XAML and CS file as I took the highlighted code only.
Helper Classes
public abstract class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propName));
}
}
}
public class CommandHandler : ICommand
{
public event EventHandler CanExecuteChanged { add { } remove { } }
private Action<object> action;
private bool canExecute;
public CommandHandler(Action<object> action, bool canExecute)
{
this.action = action;
this.canExecute = canExecute;
}
public bool CanExecute(object parameter)
{
return canExecute;
}
public void Execute(object parameter)
{
action(parameter);
}
}
ViewModel
public class ViewModel : ViewModelBase
{
private string groupAddress;
public string GroupAddress
{
get
{
return groupAddress;
}
set
{
if(value != groupAddress)
{
groupAddress = value;
OnPropertyChanged("GroupAddress");
}
}
}
public ViewModel()
{
}
private ICommand clickCommand;
public ICommand ClickCommand
{
get
{
return clickCommand ?? (clickCommand = new CommandHandler(() => MyAction(), true));
}
}
public void MyAction()
{
GroupAddress = "New Group Address";
}
}
Window Xaml
<TextBox Grid.Column="1" Grid.Row="1" Width ="80"
Text="{Binding GroupAddress, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
<Button Content="Push" Style="{StaticResource TransparentButtonStyle}"
Margin="5" Command="{Binding ClickCommand}"/>
Window Xaml cs
ViewModel vm = new ViewModel();
this.DataContext = vm;
I am trying to move from WinForms to WPF, and am stuck on binding.
I have a label:
<Label Name="labelState" Content="{Binding state}" HorizontalAlignment="Right" Margin="10,10,10,10" FontSize="12" />
In the cs of the same userControl (named FormInput), I have :
public string state { get; set; }
public FormInput()
{
state = "ok";
InitializeComponent();
}
Why doesn't this work?
Thank you.
When you are binding something in WPF you need to use INotifyPropertyChanged
Implement a class follows,
class TestObject : INotifyPropertyChanged
{
private string _state;
public string State
{
get
{
return _state;
}
set
{
if (_state == value) return;
_state = value;
OnPropertyChanged("State");
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
}
and in your FormInput
public FormInput()
{
InitializeComponent();
TestObject t = new TestObject();
labelState.DataContext = t;
t.State = "ok";
}
and XAML as follows,
<Label Name="labelState" Content="{Binding State}" HorizontalAlignment="Right" >
My ListBox doesn't react to my ObservableCollection.
This is the ListBox I am talking about.
<ListBox x:Name="CreateFieldsList"
HorizontalAlignment="Left"
Height="218"
VerticalAlignment="Top"
Width="244"
Margin="0,86,0,0"
BorderBrush="#FFB9B9B9">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid Margin="4"
Width="215"
Height="32.96"
Background="White">
<TextBlock Text="{Binding Name}"
FontWeight="Normal"
FontSize="18.667"
Padding="8,3,0,0" />
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
In my MainWindow, I prepare the data binding like this
private ObservableCollection<FieldListItem> _fieldItems;
public MainWindow()
{
InitializeComponent();
_fieldItems = new ObservableCollection<FieldListItem>();
CreateFieldsList.ItemSource = _fieldItems;
}
A FieldListItem is following
public class FieldListItem : ViewItem
{
private Field _field;
public string Name
{
get { return _field.Name; }
}
public string Value
{
get { return _field.Value; }
}
public FieldListItem(Field f)
{
_field = f;
}
}
and finally the ViewItem
public class ViewItem : INotifyPropertyChanged
{
private event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged([CallerMemberName] string caller = "")
{
if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(caller));
}
//The interface forces me to implement this. Why?
event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged
{
add { }
remove { }
}
}
I don't know why this isn't working. Could you please help?
The INotifyPropertyChanged interface needs you to implement an event. Your event implementation does not work because registrations and deregistrations are ignored because the add and remove blocks are empty.
Implement the event without add and remove:
public class ViewItem : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged([CallerMemberName] string caller = "")
{
var copy = PropertyChanged;
if (copy != null)
copy(this, new PropertyChangedEventArgs(caller));
}
}
I need Model to notify ViewModel if any property is changed, because I need to collect the changed model instances in a collection for further processing, also to enable and disable command buttons in the viewmodel.
So I've used ModelBase abstract class and added HasChanges property which I can test against in the viewmodel and catch the changed models.But it is not working and I don't know what i'm missing.
public abstract class ModelBase : INotifyPropertyChanged
{
protected ModelBase()
{
}
private bool _hasChanges;
public bool HasChanges
{
get
{
return _hasChanges;
}
set
{
if (_hasChanges != value)
{
_hasChanges = value;
RaisePropertyChanged("HasChanges");
}
}
}
protected void RaisePropertyChanged(string propertyName)
{
HasChanges = true;
this.OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
{
var handler = this.PropertyChanged;
if (handler != null)
{
handler(this, e);
}
}
}
The Model is wrapped inside the ViewModel and bound to the View which is a DataGrid:
private Model_selectedModel;
public Mode SelectedModel
{
get
{
return _selectedModel;
}
set
{
if (_selectedModel != value)
{
_selectedModel = value;
NotifyPropertyChanged("SelectedModel");
}
}
}
Thanks for valuable help.
I tested your class and it's okay. I think the point is a typo here:
private Model_selectedModel;
public Mode SelectedModel
{
get
{
return _selectedModel;
}
set
{
if (_selectedModel != value)
{
_selectedModel = value;
NotifyPropertyChanged("SelectedModel");
}
}
}
There should be RaisePropertyChanged instead of NotifyPropertyChanged.
Below it's my test:
XAML
<Window x:Class="TestUpdatePropertyChanged.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:this="clr-namespace:TestUpdatePropertyChanged"
Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
<this:TestViewModel />
</Window.DataContext>
<Grid>
<TextBox Width="100" Height="25" Text="{Binding Path=TestString, UpdateSourceTrigger=PropertyChanged}" />
<Button Width="100" Height="30" VerticalAlignment="Top" Content="Click" Click="Button_Click" />
</Grid>
</Window>
Code-behind
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void Button_Click(object sender, RoutedEventArgs e)
{
var testData = this.DataContext as TestViewModel;
testData.TestString = "Yay, it's change!";
if (testData.HasChanges == true)
{
MessageBox.Show("It's Change!");
}
}
}
public class TestViewModel : ModelBase
{
private string _testString = "test";
public string TestString
{
get { return _testString; }
set
{
if (_testString != value)
{
_testString = value;
RaisePropertyChanged("TestString");
}
}
}
}
public abstract class ModelBase : INotifyPropertyChanged
{
protected ModelBase()
{
}
private bool _hasChanges;
public bool HasChanges
{
get
{
return _hasChanges;
}
set
{
if (_hasChanges != value)
{
_hasChanges = value;
RaisePropertyChanged("HasChanges");
}
}
}
protected void RaisePropertyChanged(string propertyName)
{
HasChanges = true;
this.OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
{
var handler = this.PropertyChanged;
if (handler != null)
{
handler(this, e);
}
}
}
I'm trying to bind a string property to show in my status bar if my database is connected. Here's the code:
C#
public class TimeBase : INotifyPropertyChanged
{
private DXTickDB db;
string[] args = new string[] { };
public event PropertyChangedEventHandler PropertyChanged;
private bool isTBconnected;
public string connectionStatus { get; set; }
public bool tb_isconnected
{
get { return isTBconnected; }
set
{
if (value != isTBconnected)
{
isTBconnected = value;
if(isTBconnected == false)
{
connectionStatus = "TimeBase is not connected";
}
else
{
connectionStatus = "TimeBase is connected";
}
OnPropertyChanged("connectionStatus");
}
}
}
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
#region TimeBase Connection
public void ConnectToTimeBase()
{
if (args.Length == 0)
args = new string[] { "not available for security reasons" };
db = TickDBFactory.createFromUrl(args[0]);
try
{
db.open(true);
tb_isconnected = true;
}
catch
{
tb_isconnected = false;
}
}
#endregion
This is the Xaml for the status bar in my main window:
<StatusBar Height="23" DockPanel.Dock="Bottom" Background="Green">
<StatusBarItem>
<StackPanel Orientation="Horizontal">
<TextBlock
Foreground="{StaticResource Foreground}"
Text="{Binding Path=connectionStatus}">
</TextBlock>
</StackPanel>
</StatusBarItem>
</StatusBar>
I'm trying to bind it to the string property connectionStatus but no text appears even though when I debug it I can see connectionStatus updated. Any suggestions to what's wrong here?
DataContext property should contain your model like so:
TimeBase timeBaseInstance;
public MainWindow()
{
timeBaseInstance = new TimeBase();
//Set the dataContext so bindings can iteract with your data
DataContext = timeBaseInstance;
InitializeComponent();
}