I am new to WPF and tring to learn a WPF composite application.
I have got user control which is a module which 1 label and 1 button on it.
Now I am trying to use the Command property on button which looks like
<Button Name="button1" Command="{Binding Path = GetCustomerNameCommand}">GetCustomer</Button>
In the presenter I have got
public class HelloWorldPresenter : PresenterBase<IHelloWorldView>
{
private readonly IWpfService _wpfService;
public HelloWorldViewModel CustomerViewModel { get; set; }
public ICommand GetCustomerNameCommand { get; set; }
public HelloWorldPresenter(IHelloWorldView view, IWpfService wpfService)
: base(view)
{
_wpfService = wpfService;
GetCustomerNameCommand = new DelegateCommand<string>(GetCustomerName);
View.Presenter = this;
PopulateViewModel(string.Empty);
}
private void GetCustomerName(string obj)
{
throw new NotImplementedException();
}
private void PopulateViewModel(string test)
{
CustomerViewModel = new HelloWorldViewModel { Name = _wpfService.GetCustomer() };
}
}
The thing is GetCustomerName() method is not getting executed when i click the Button
I found it, i was adding the same view 2 times which was creating the problem...
Related
I have an application that look like this
The whole window is defined in the MainWindow.xaml, the green part is the content control
<ContentControl Grid.Row="1"
Grid.Column="1"
Margin="5"
Content="{Binding CurrentView}"/>
The MainViewModel looks like this:
public RelayCommand HomeViewCommand { get; set; }
public RelayCommand DetailsViewCommand { get; set; }
public HomeViewModel HomeVm { get; set; }
public DetailsViewModel DetailsVm { get; set; }
private object _currentView;
public object CurrentView
{
get { return _currentView; }
set
{
_currentView = value;
OnPropertyChanged();
}
}
public MainViewModel()
{
HomeVm = new HomeViewModel();
DetailsVm = new DetailsViewModel();
CurrentView = HomeVm;
HomeViewCommand = new RelayCommand(o =>
{
CurrentView = HomeVm;
});
}
Current and default content of the MainView is the HomeView, I already implemented the event trigger on pressing the item in the list in the HomeView. I want to know, what should I write in the HomeView method (which is triggering on the click on the item) in order to change the MainView content part to another View (DetailsView in my case). Code in my HomeViewModel:
private void RaisePropertyChanged(string propertyName)
{
var handler = PropertyChanged;
if (handler != null)
{
//something here to change the currentView of the MainViewModel
}
}
Got an answer from the guy from discord server.https://discord.gg/AvnpSMDY
You could pass the MainViewModel into the constructor of another view model and assign it to a private readonly field like _mainViewModel. This way you can change the current view either by changing the CurrentView property:
_mainViewModel.CurrentView = _mainViewModel.DetailsVm;
or executing commands:
_mainViewModel.DetailsViewCommand.Execute(null);
I have a WPF application and I want the Start button control only enabled if they have to have specified a value in the text box for 'Download Path'.
My ViewModel contains a property for my model "ConfigurationSettings" and an ICommand implementation (CommandImp) for the button:
public class MainWindowViewModel : BaseNotifyPropertyChanged
{
private ConfigurationSettings _configurationSettings { get; set; }
public ConfigurationSettings ConfigurationSettings
{
get
{
return _configurationSettings;
}
set
{
if (_configurationSettings != value)
{
_configurationSettings = value;
RaisePropertyChanged("ConfigurationSettings");
}
}
}
public CommandImp StartCommand { get; set; } // this is an implementation of ICommand
public MainWindowViewModel()
{
StartCommand = new CommandImp(OnStart, CanStart);
_configurationSettings = new ConfigurationSettings();
_configurationSettings.PropertyChanged += delegate (object o,
PropertyChangedEventArgs args)
{
StartCommand.RaiseCanExecuteChanged(); // break point here is never reached
};
}
private bool CanStart()
{
if (!String.IsNullOrEmpty(ConfigurationSettings.DownloadPath))
{
return true;
}
return false;
}
}
In my XAML I have a Start button and the with Command = "{Binding StartCommand}".
My ConfigurationSettings class just has a string for the DownloadPath which is bound to a textbox in the XAML:
public class ConfigurationSettings : BaseNotifyPropertyChanged
{
private string _downloadPath { get; set; }
public string DownloadPath
{
get { return _downloadPath; }
set
{
if (_downloadPath != value)
{
_downloadPath = value;
RaisePropertyChanged("DownloadPath"); // break point here IS reached
}
}
}
}
When the user enters a DownloadPath, I expect it to be triggering the PropertyChanged Event, and running my delegate method defined in the ViewModel constructor.
If I move the Command Button inside the ConfigurationSettings class I can do away with event subscription and just use StartCommand.RaiseCanExecuteChanged() right beneath RaisePropertyChanged("DownloadPath");. But I don't want the ICommand as part of my Model.
How can I trigger CanStart() when one of the properties of ConfigurationSettings changes?
UPDATE:
Here is the XAML for the text box binding:
<TextBlock Text="{Binding ConfigurationSettings.DownloadPath, Mode=TwoWay, UpdateSourceTrigger=LostFocus}" TextWrapping="WrapWithOverflow" />
And the button:
<Button Content="Start" Command="{Binding StartCommand}"></Button>
I should note that the bindings are working correctly. When I update the textblock, I can see in the ViewModel that ConfigurationSettings.DownloadPath is correctly being updated.
BaseNotifyPropertyChanged is an implementation of INotifyPropertyChanged like so:
public class BaseNotifyPropertyChanged : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void RaisePropertyChanged(string property)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(property));
}
}
I don't seem to be having any issues with the property changed event. I can put a break point in here and it is hit when I update the DownloadPath text box. It's when I subscribe to this PropertyChanged event in my ViewModel constructor, my delegate method isn't firing.
Hate to answer my own question but the people commenting made me think about restructuring my question - which led me to the answer before needing to make another update.
The solution was to move my event subscription inside the 'set' function for ConfigurationSettings:
private ConfigurationSettings _configurationSettings { get; set; }
public ConfigurationSettings ConfigurationSettings
{
get
{
return _configurationSettings;
}
set
{
if (_configurationSettings != value)
{
_configurationSettings = value;
_configurationSettings = new Model.ConfigurationSettings();
_configurationSettings.PropertyChanged += (o, args) =>
{
StartCommand.RaiseCanExecuteChanged();
};
RaisePropertyChanged("ConfigurationSettings");
}
}
}
The problem was where I was setting my Data Context which I did not originally suspect was at all the problem. I load the view model from an XML file on disk. And when the application is closed, I overwrite that file with the latest ViewModel.
In the constructor I was reading and setting the DataContext:
public MainWindowView()
{
InitializeComponent();
string appPath = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().CodeBase);
DataSourcePath = new Uri(System.IO.Path.Combine(appPath, DataFileName));
if (File.Exists(DataSourcePath.LocalPath))
{
XmlReader reader = XmlReader.Create(DataSourcePath.LocalPath);
DataContext = (MainWindowViewModel)serialize.Deserialize(reader);
reader.Close();
}
else
{
WriteDataViewModelToDisk(); // new empty view model written to disk
}
}
If this was the first time I ran the code, with no pre-existing file, my delegate event handler actually worked. The issue was when this code loaded a pre-existing XML file, it overwrote the ConfigurationSettings property in my view model - thus destroying the event subscription.
To simplify situation. I have MainWindow with two user controls, all of them have corresponding Viewmodels. Everything works fine, properties bind and so on, beside one functionality.
I want to refresh data on second user control after event happened in the first one. Unfortunetly in this scenario, PropertyChanged event (derived from INotifyPropertyChanged, defined in ViewModelBase) is null.
However, if I raise an event from second user control, property on view gets updated as expected!
public class MainWindowViewModel : ViewModelBase
{
public FirstUserControl FirstUserControl {get; set;}
public SecondUserControl SecondUserControl {get; set;}
public MainWindowViewModel ()
{
FirstUserControl =new FirstUserControl();
FirstUserControl.RaiseClicked+=OnRaiseClicked;
SecondUserControl = new SecondUserControl();
SecondUserControl .RaiseClicked+=OnRaiseClicked;
}
private void OnRaiseClicked(object sender, EventArgs e)
{
SecondUserControl.RefreshView();
}
}
public class FirstUserControl : ViewModelBase
{
public ICommand Raise { get; private set; }
public EventHandler RaiseClicked {get;set;}
public FirstUserControl ()
{
Raise = new RelayCommand( p=> RaiseClicked(this, null));
}
}
public class SecondUserControl: ViewModelBase
{
public ICommand Raise { get; private set; }
public EventHandler RaiseClicked {get;set;}
public string Title
{
get
{
return MyLogic.GetCurrentTitle(); // debuggers enter here only while event on second user control raised
}
}
public void RefreshView()
{
OnPropertyChanged("Title"); // debugger enter here in cases
}
}
I suppose there is something with threads going on, but I'm not that familiar with WPF to work out it by my own. Can someone help how to quickly and easy make event from first UC refresh data on the second?
Trying to understand how to bind this static list to a combobox that located on different window.
public partial class MainWindow : Window
{
public static List<Classes.Entity> EntityList { get; set; }
public MainWindow()
{
EntityList = new List<Classes.Entity>();
InitializeComponent();
}
...
the object:
public class Entity
{
public string entityName { get; set; }
...
XAML (In a diffrent window, call "NewRelationship.xaml.cs"
<ComboBox x:Name="cb_from" ItemsSource="{Binding Path=EntityList}" DisplayMemberPath="entityName" SelectedValue="{Binding Path=Entity}" />
Of course I fill the list later in the code...
if I moving the list to the newRelationship window and add "this.datacontext = this;" its working,
How do I make this work when the list is in the mainWindow? Thanks...
A better approach would be to keep the EntityList in a separate object that both windows could reference:
class ViewModel
{
private List<Classes.Entity> _entityList = new List<Classes.Entity>();
public IEnumerable<Classes.Entity> EntityList
{
get { return _entityList; }
}
}
partial class MainWindow
{
public MainWindow()
{
InitializeComponent();
this.DataContext = new ViewModel();
}
}
When the second window is created, you can pass an instance of the ViewModel class to it, and set it as the DataContext.
I have an issue with something that should be very simple databinding scenario. I want to bind a list of items. I want to create a user control put it in a ItemsControl's template and bind the ItemsControl to some data. I am perfectly happy with one time databinding so I was kind of hoping to avoid learning about dependency properties and all the databinding stuff for this simple scenario.
Here is the XAML for the user control:
<TextBlock>Just Something</TextBlock>
And the code behind:
namespace TestWindowsPhoneApplication
{
public partial class TestControl : UserControl
{
public TestData SomeProperty { get; set; }
public String SomeStringProperty { get; set; }
public TestControl()
{
InitializeComponent();
}
}
}
MainPage.xaml:
<ItemsControl Name="itemsList" ItemsSource="{Binding}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<t:TestControl SomeStringProperty="{Binding Path=SomeString}"></t:TestControl>
<!--<TextBlock Text="{Binding Path=SomeString}"></TextBlock>-->
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Here is MainPage.xaml.cs:
namespace TestWindowsPhoneApplication
{
public class TestData
{
public string SomeString { get; set; }
}
public partial class MainPage : PhoneApplicationPage
{
// Constructor
public MainPage()
{
InitializeComponent();
itemsList.DataContext = new TestData[] { new TestData { SomeString = "Test1" }, new TestData { SomeString = "Test2" } };
}
}
}
When I run the project I get an error "the parameter is incorrect". I also tried binding directly to the item with SomeProperty={Binding} since that is what I actually want to do but this causes the same error. If I try doing the same thing with the TextBlock control (the commented line) everything works fine.
How can I implement this simple scenario?
To make a property on your custom control "bindable" you have to make it a dependency property. Check out my answer here for a nice simple example of doing just this on a custom control: passing a gridview selected item value to a different ViewModel of different Usercontrol
public string SomeString
{
get { return (string)GetValue(SomeStringProperty); }
set { SetValue(SomeStringProperty, value); }
}
public static readonly DependencyProperty SomeStringProperty =
DependencyProperty.Register("SomeString", typeof(string), typeof(TestControl),
new PropertyMetadata(string.Empty, new PropertyChangedCallback(OnSomeStringChanged)));
private static void OnSomeStringChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
((TestControl)d).OnSomeStringChanged(e);
}
protected virtual void OnSomeStringChanged(DependencyPropertyChangedEventArgs e)
{
//here you can do whatever you'd like with the updated value of SomeString
string updatedSomeStringValue = e.NewValue;
}