Develop Reference

Xamarin XAML to C# Data Trigger

In reference to this question below I have XAML working, but am struggling with converting to C#
Xamarin / MAUI XAML to C#
Here is my attempt that isn't working and I'm not sure why... My goal is when LayoutState.Success it updated via VenuePageViewModel, VenueSuccessContentView should display inside the cvWrap ContentView on the Page.
public partial class VenuePageViewModel : ObservableObject
{
[ObservableProperty]
private LayoutState layoutState = LayoutState.Loading;
public VenuePageViewModel()
{
LayoutState = LayoutState.Success;
}
}
public class VenueSuccessContentView : ContentView
{
public VenueSuccessContentView()
{
Content = new Label() { Text = "hello world", TextColor = Colors.Red };
}
}
public class MainPageCS : ContentPage
{
public MainPageCS()
{
BindingContext = new VenuePageViewModel();
var venueSuccessCV = new VenueSuccessContentView();
Resources.Add(nameof(LayoutState.Success), venueSuccessCV);
var cvWrap = new ContentView();
var cv = new ContentView();
cvWrap.Content = cv;
Content = cvWrap;
var datatrigger = new DataTrigger(typeof(ContentView))
{
Binding = new Binding(source: RelativeBindingSource.TemplatedParent, path: nameof(VenuePageViewModel.LayoutState)),
Value = LayoutState.Success,
Setters = {
new Setter { Property = ContentView.ContentProperty, Value = venueSuccessCV },
}
};
cvWrap.Triggers.Add(datatrigger);
}
}
Minimal Repo: https://github.com/aherrick/DataTriggerCSharpMaui

The binding path is incorrect in DataTrigger .
Modify Binding property of DataTrigger as below .
Binding = new Binding( path: nameof(VenuePageViewModel.LayoutState))

Memory leak on CanExecuteChanged using Catel Command

I was profiling a WPF application that uses Catel as MVVM Framework and I've seen that in a ViewModel I've got 2 retention path as
Now I create such RadMenuItem in a behavior I attach to the context menu and they're defined as
protected virtual IEnumerable<RadMenuItem> GetRowMenuItems(RadContextMenu contextMenu)
{
var rowItems = new List<RadMenuItem>();
RadMenuItem saveSettings = new RadMenuItem
{
Tag = "force",
Header = CoreResources.LBL_SAVE_SETTINGS,
Command = DefaultRtViewContextMenuCommands.SaveLayoutDataCommand,
CommandParameter = AssociatedObject,
Icon = new Image { Source = new BitmapImage(new Uri("pack://application:,,,/IF.Tesoreria.Client.WPF.Core;component/Media/save.png")) }
};
rowItems.Add(saveSettings);
RadMenuItem loadSettings = new RadMenuItem
{
Tag = "force",
Header = CoreResources.LBL_LOAD_SETTINGS,
Command = DefaultRtViewContextMenuCommands.LoadLayoutDataCommand,
CommandParameter = AssociatedObject,
Icon = new Image { Source = new BitmapImage(new Uri("pack://application:,,,/IF.Tesoreria.Client.WPF.Core;component/Media/load.png")) }
};
Now The commands are defined in
public class DefaultRtViewContextMenuCommands
{
public static Command<FlexGridCommandParameter> SaveLayoutDataCommand { get; private set; }
public static Command<FlexGridCommandParameter> LoadLayoutDataCommand { get; private set; }
private static void OnLoadLayoutCommandExecute(FlexGridCommandParameter grid)
{
Argument.IsNotNull(() => grid);
var dependencyResolver = DependencyResolverManager.Default;
var openFileService = dependencyResolver.DefaultDependencyResolver.Resolve<IOpenFileService>();
openFileService.Filter = "Gridview setting file|*.flexgrid";
if (openFileService.DetermineFile())
{
// User selected a file
using (var fs = File.OpenRead(openFileService.FileName))
{
GridViewPersistenceHelper.LoadLayout(grid.Grid, fs, null);
}
}
}
private static void OnSaveLayoutCommandExecute(FlexGridCommandParameter grid)
{
Argument.IsNotNull(() => grid);
var dependencyResolver = DependencyResolverManager.Default;
var saveFileService = dependencyResolver.DefaultDependencyResolver.Resolve<ISaveFileService>();
saveFileService.Filter = "Gridview setting file|*.flexgrid";
if (saveFileService.DetermineFile())
{
// User selected a file
using (var fs = File.OpenWrite(saveFileService.FileName))
{
GridViewPersistenceHelper.SaveLayout(grid.Grid, fs);
}
}
}
static DefaultRtViewContextMenuCommands()
{
viewModelFactory = ServiceLocator.Default.ResolveType<IViewModelFactory>();
portfolioService = ServiceLocator.Default.ResolveType<IPortfoliosService>();
pkInstrumentsService = ServiceLocator.Default.ResolveType<IPkInstrumentsService>();
SaveLayoutDataCommand = new Command<FlexGridCommandParameter>(OnSaveLayoutCommandExecute,_=>true);
LoadLayoutDataCommand = new Command<FlexGridCommandParameter>(OnLoadLayoutCommandExecute,_=>true);
}
What am I doing wrong?
Thanks

radMenuItem.Command = null;
Works for me. You can decompile and see that when you do it, the menu item unregisters himself from the Command’s CanExecuteChanged

Implementing Xamarin Forms context actions

I am trying to implement context actions on my list in Xamarin Forms but can't get it to work.
I am not using XAML, but instead creating my layout in code.
I am trying to follow the steps in https://developer.xamarin.com/guides/xamarin-forms/user-interface/listview/interactivity/#Context_Actions and I want to push a new page when "Edit" is clicked.
I cleaned up my code and removed my feeble attempts to make things work.
So this is my custom list cell:
public class PickerListCell : TextCell
{
public PickerListCell ()
{
var moreAction = new MenuItem { Text = App.Translate ("Edit") };
moreAction.SetBinding (MenuItem.CommandParameterProperty, new Binding ("."));
moreAction.Clicked += async (sender, e) => {
var mi = ((MenuItem)sender);
var option = (PickerListPage.OptionListItem)mi.CommandParameter;
var recId = new Guid (option.Value);
// This is where I want to call a method declared in my page to be able to push a page to the Navigation stack
};
ContextActions.Add (moreAction);
}
}
And here is my model:
public class OptionListItem
{
public string Caption { get; set; }
public string Value { get; set; }
}
And this is the page:
public class PickerPage : ContentPage
{
ListView listView { get; set; }
public PickerPage (OptionListItem [] items)
{
listView = new ListView () ;
Content = new StackLayout {
Children = { listView }
};
var cell = new DataTemplate (typeof (PickerListCell));
cell.SetBinding (PickerListCell.TextProperty, "Caption");
cell.SetBinding (PickerListCell.CommandParameterProperty, "Value");
listView.ItemTemplate = cell;
listView.ItemsSource = items;
}
// This is the method I want to activate when the context action is called
void OnEditAction (object sender, EventArgs e)
{
var cell = (sender as Xamarin.Forms.MenuItem).BindingContext as PickerListCell;
await Navigation.PushAsync (new RecordEditPage (recId), true);
}
}
As you can see by my comments in the code, I have indicated where I believe things are missing.
Please assist guys!
Thanks!

Probably is too late for you, but can help others. The way i've found to do this is passing the instance of page on creation the ViewCell.
public class PickerListCell : TextCell
{
public PickerListCell (PickerPage myPage)
{
var moreAction = new MenuItem { Text = App.Translate ("Edit") };
moreAction.SetBinding (MenuItem.CommandParameterProperty, new Binding ("."));
moreAction.Clicked += async (sender, e) => {
var mi = ((MenuItem)sender);
var option = (PickerListPage.OptionListItem)mi.CommandParameter;
var recId = new Guid (option.Value);
myPage.OnEditAction();
};
ContextActions.Add (moreAction);
}
}
So, in your page:
public class PickerPage : ContentPage
{
ListView listView { get; set; }
public PickerPage (OptionListItem [] items)
{
listView = new ListView () ;
Content = new StackLayout {
Children = { listView }
};
var cell = new DataTemplate(() => {return new PickerListCell(this); });
cell.SetBinding (PickerListCell.TextProperty, "Caption");
cell.SetBinding (PickerListCell.CommandParameterProperty, "Value");
listView.ItemTemplate = cell;
listView.ItemsSource = items;
}
void OnEditAction (object sender, EventArgs e)
{
var cell = (sender as Xamarin.Forms.MenuItem).BindingContext as PickerListCell;
await Navigation.PushAsync (new RecordEditPage (recId), true);
}
}

Ok, so with the help of some posts, specifically this one https://forums.xamarin.com/discussion/27881/best-practive-mvvm-navigation-when-command-is-not-available, I came to the following solution, though I'm not perfectly satisfied with the way it looks.
My custom cell now announces when a command is being executed using MessagingCenter:
public class PickerListCell : TextCell
{
public PickerListCell ()
{
var moreAction = new MenuItem { Text = App.Translate ("Edit") };
moreAction.SetBinding (MenuItem.CommandParameterProperty, new Binding ("."));
moreAction.Clicked += async (sender, e) => {
var mi = ((MenuItem)sender);
var option = (PickerListPage.OptionListItem)mi.CommandParameter;
var recId = new Guid (option.Value);
// HERE I send a request to open a new page. This looks a
// bit crappy with a magic string. It will be replaced with a constant or enum
MessagingCenter.Send<OptionListItem, Guid> (this, "PushPage", recId);
};
ContextActions.Add (moreAction);
}
}
And in my PickerPage constructor I added this subscription to the Messaging service:
MessagingCenter.Subscribe<OptionListItem, Guid> (this, "PushPage", (sender, recId) => {
Navigation.PushAsync (new RecordEditPage (recId), true);
});
All this works just find, but I'm not sure if this is the way it was intended to. I feel like the binding should be able to solve this without the Messaging Service, but I can't find out how to bind to a method on the page, only to a model, and I don't want to pollute my model with methods that have dependencies on XF.

Passing a list that includes a nested list of datetimes on command execution not working in wpf

I have a rather strange requirement for a Wpf Project I'm working on. I want to be able to build a XamDataGrid with a series of DateTime fields when the user saves the data from another grid. Currently I see the second XamDataGrid with it's fields, but upon execution of the command that saves the data, although I can see in the debugger that my second list (which is bound to the second XamDataGrid) is generated, nothing displays on this second XamDataGrid.
I'll post most of my code so that somebody might help me:
The xaml (for the second datagrid as the first one is working fine):
<igDP:XamDataGrid.FieldLayouts>
<igDP:FieldLayout>
<igDP:Field Label="ID" Name="id" Width="50"></igDP:Field>
<igDP:Field Label="Descripcion" Name="descripcion" Width="400"></igDP:Field>
<igDP:UnboundField Label="Fechas de Pago" Name="cadaPago" Width="400">
</igDP:UnboundField>
<igDP:Field Label="Colores" Name="Colores" Visibility="Collapsed" />
</igDP:FieldLayout>
</igDP:XamDataGrid.FieldLayouts>
</igDP:XamDataGrid>
`
The code in my viewmodel for the second grid:
public List<ClaseFechasPago> ListaFechasPago
{
get { return listaFechasPago; }
set { listaFechasPago = value; notifyChanges("ListaFechasPago"); }
}
public void PintarFechas(List<ClaseFechasPago> f)
{
ListaFechasPago.Clear();
foreach (ClaseFechasPago fecha in f)
{
fecha.cadaPago = new List<DateTime>();
for (int i = 0; i < fecha.numPagos; i++)
{
fecha.cadaPago.Add(new DateTime());
}
ListaFechasPago.Add(fecha);
}
}
public vmCursos_y_Diplomados()
{
Comando = new cmdCursos_y_Diplomados();
Comando.ViewModel = this;
ListaCursosyDiplomados = new List<ClaseCursosyDiplomados>();
ListaFechasPago = new List<ClaseFechasPago>();
this.cargarDatos();
this.PintarFechas(ListaFechasPago);
}
Now on the command I'm doing the following
public void Execute(object parameter)
{
List<CatEntidadesEducacionContinua> cursos = new List<CatEntidadesEducacionContinua>();
List<ClaseFechasPago> fechas = new List<ClaseFechasPago>();
foreach (ClaseCursosyDiplomados C in ViewModel.ListaCursosyDiplomados.Where(t=>t.Colores==1).ToList())
{
cursos.Add(new CatEntidadesEducacionContinua
{
IdEntidadEducacionContinua = C.id, Coordinador=C.coordinador, Descripcion=C.descripcion, FechaUltimoCambio = DateTime.Now,
FechaInicio = C.fechaInicio, FechaTermino=C.fechaTermino, Precio=C.precio, NumeroDePagos=C.numeroDePagos, FechasPagos=C.fechasPagos, Inhabilitado=C.inhabilitado,
});
if (C.numeroDePagos > 1)
{
ClaseFechasPago f = new ClaseFechasPago();
f.numPagos = C.numeroDePagos;
f.descripcion = C.descripcion;
f.id = C.id;
fechas.Add(f);
}
}
System.Windows.MessageBox.Show(new Entidades.MetodoCursos_y_Diplomados().SetEntidadEContinua(cursos), "Entidades de Educación Continua", System.Windows.MessageBoxButton.OK, System.Windows.MessageBoxImage.Information);
//System.Windows.MessageBox.Show(new Entidades.MetodoFechasPago().pintarFechasPago
ViewModel.cargarDatos();
ViewModel.PintarFechas(fechas);
}
But as I said it's not working, the execution results in the following screenshot, where the second grid is not populated:
Oh and I also forgot earlier to show the code for my custom class, out of which the list bound to the XamDataGrid is made of:
public class ClaseFechasPago : Utils.PropertyChange
{
private List<DateTime> _cadaPago;
public List<DateTime> cadaPago
{
get { return _cadaPago; }
set
{
_cadaPago = value;
if (EntroPrimeraVez)
{
Colores = 1;
}
}
}
private int? _numPagos;
public int? numPagos
{
get { return _numPagos; }
set
{
_numPagos = value;
if (EntroPrimeraVez)
{
Colores = 1;
}
}
}
private int _id;
public int id
{
get { return _id; }
set
{
_id = value;
}
}
private string _descripcion;
public string descripcion
{
get { return _descripcion; }
set { _descripcion = value; }
}
private int _Colores;
private bool _EntroPrimeraVez;
public bool EntroPrimeraVez
{
get { return _EntroPrimeraVez; }
set { _EntroPrimeraVez = value; notifyChanges("EntroPrimeraVez"); }
}
public int Colores
{
get { return _Colores; }
set { _Colores = value; notifyChanges("Colores"); }
}
}

It turned out the only thing I needed to do was passing the List explicitly as a list, like so:
ListaFechasPago = ListaFechasPago.ToList()
However, I seemed to have a mistake of concept in the way I was building the date fields. I ended up building as many registries as were needed of the same entry and binding a DateTime field to each, like so:
public static List<ClaseFechasPago> PintarFechas(ClaseFechasPago f)
{
List<ClaseFechasPago> ListaFechasPago = new List<ClaseFechasPago>();
for (int i = 0; i < f.numPagos; i++)
{
ClaseFechasPago fecha = new ClaseFechasPago();
fecha.cuotaInscripcion = 0M;
fecha.Inscripcion = true;
fecha.fechaPago = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day);
fecha.id = f.id;
fecha.descripcion = f.descripcion;
fecha.numPagos = f.numPagos;
fecha.Colores = f.Colores;
fecha.EntroPrimeraVez = f.EntroPrimeraVez;
ListaFechasPago.Add(fecha);
}
return ListaFechasPago;
//ListaFechasPago = ListaFechasPago.ToList();
}
Oh and of course initialize the ListaFechasPago List in the class that is set as DataContext for the window:
ListaFechasPago = new List<ClaseFechasPago>();
insde the class vmCursos_y_Diplomados
because I do:
private void UserControl_Loaded(object sender, RoutedEventArgs e)
{
this.DataContext = new vmCursos_y_Diplomados();
}

pivot view with dynamic data

i'm working on a windows phone application using pivot view to preview data for the user, the data comes from a web service, then i put it in List then i add the item to the pivot view
but when i call the web service the view doesn't wait till i get the data from the server to add to the view and the view adds nothing , here is my code
public class downloads : List<Downloaded>
{
List<string> downoladedList = new List<string>();
public downloads()
{
BuildCollection();
}
//private const string IMG_PATH = "../Images/";
public ObservableCollection<Downloaded> DataCollection { get; set; }
public ObservableCollection<Downloaded> BuildCollection()
{
// int x=0;
Downloaded downObject = new Downloaded();
ServiceReference1.Service1Client service = new ServiceReference1.Service1Client();
service.GetDownloadsCompleted += new EventHandler<ServiceReference1.GetDownloadsCompletedEventArgs>(GetDownLoads);
System.Threading.Thread.Sleep(100000);
service.GetDownloadsAsync(20019);
DataCollection = new ObservableCollection<Downloaded>();
foreach (var elem in downoladedList)
{
string[] elemProp = new string[8];
elemProp = elem.Split('=');
if (elemProp[3] == "1")
elemProp[3] = "downloaded";
else
elemProp[3] = "in progress";
DataCollection.Add(new Downloaded(elemProp[1], elemProp[3], "test.png"));
}
return DataCollection;
}
public void GetDownLoads(object sender, ServiceReference1.GetDownloadsCompletedEventArgs e)
{
try
{
downoladedList = e.Result.ToList<string>();
}
catch (Exception ee)
{
}
}
}

You cannot call thread.sleep. This will block entire UI thread.
Declare DataCollection = new ObservableCollection();
outside scope.
You should put all your code on completed like this :
public void GetDownLoads(object sender, ServiceReference1.GetDownloadsCompletedEventArgs e)
{
try
{
downoladedList = e.Result.ToList<string>();
foreach (var elem in downoladedList)
{
string[] elemProp = new string[8];
elemProp = elem.Split('=');
if (elemProp[3] == "1")
elemProp[3] = "downloaded";
else
elemProp[3] = "in progress";
DataCollection.Add(new Downloaded(elemProp[1], elemProp[3], "test.png"));
}
}
catch (Exception ee)
{
}
}