I am trying to binding a number to a Enum located in the view model. I haven't been able to pass the value from the view to the viewmodel through the converter. Is this even possible? I haven't seen anything online that solves this and none of my attemps have worked either.
Viewmodel
public enum TimerOptions
{
FifteenMinutes,
OneHour,
Tomorrow
}
private ICommand _timerCommand;
public ICommand TimerCommand => _timerCommand ??
(_timerCommand = new RelayCommand<TimerOptions>(StartTimer));
private async void StartTimer(TimerOptions option){ .... }
View
<Button Command="{Binding TimerCommand}"
Tag="0"
CommandParameter="{Binding Path=Tag, Converter={StaticResource BidirectionalEnumConverter}}">15 minutes</Button>
In the above example, when the user clicks the button, I want my function to get the first enum value of FifteenMinutes as the parameter. I've tried this by adding a Tag (as seen), adding an x:Name to the Button and also playing around with Source and Path in the binding. Nothing has worked.
Is this possible? I've been trying to solve this for hours, I haven't found anything online.
I want my function to get the first enum value of FifteenMinutes as the parameter.
Why not just do the converter operation in the VM from the info passed in on a string in the command parameter?
Example
<Button Command="{Binding TimerCommand}"
Tag="1"
CommandParameter=1
Then have a ICommand based on that such as
public ICommand TimerCommand =>
new OperationCommand(async (oTag) => await StartTime(oTag).ConfigureAwait(true));
private bool IsOperation { get; set; }
private async void StartTimer(object oTag)
{
int tagId = (int)oTag;
//.... do the convert operations here...
...
// Access VM properties here
IsOperation = true;
await ....;
}
Here is the commanding structure I use instead of Relay.
public class OperationCommand : ICommand
{
#region Variables
private Func<object, bool> CanExecuteHandler { get; set; }
private Action<object> ExecuteActionHandler { get; set; }
public bool InSeparateThread { get; set; }
#endregion
#region Properties
#endregion
#region Construction/Initialization
public OperationCommand(Action<object> executeAction, bool inSeparateThread = false)
{
InSeparateThread = inSeparateThread;
ExecuteActionHandler = executeAction
?? throw new ArgumentNullException(nameof(executeAction));
}
public OperationCommand(Action<object> executeAction,
Func<object, bool> canExecute) : this(executeAction)
{
CanExecuteHandler = canExecute;
}
// Here to adhere to ICommand, change to below if needed
//public event EventHandler CanExecuteChanged;
event EventHandler ICommand.CanExecuteChanged
{
add {}
remove {}
}
#endregion
#region Methods
public bool CanExecute(object parameter) => CanExecuteHandler?.Invoke(parameter) ?? true;
// public void RaiseCanExecuteChanged() => CanExecuteChanged?.Invoke(this, new EventArgs());
public void Execute(object parameter)
{
ExecuteActionHandler?.Invoke(parameter);
}
#endregion
}
}
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);
My model, viewmodel and XAML is as follows:
This is my ViewModelClass:
class AllResultsViewModel
{
private ICommand _clickCommand;
public ICommand ClickCommand
{
get
{
return _clickCommand ?? (_clickCommand = new CommandHandler(param => this.MyAction(_cvm),
param => this._canExecute));
}
}
private bool _canExecute;
private ComboBoxViewModel _cvm;
public DataTable AllResults { get; set; }
public AllResultsViewModel(ComboBoxViewModel CVM)
{
_canExecute = true;
_cvm = CVM;
}
public void MyAction(ComboBoxViewModel cvm)
{
//Connecting to DB to retrieve data in datatable
}
}
public class CommandHandler : ICommand
{
private Action<object> _execute;
// private bool _canExecute;
private Predicate<object> _canExecute;
#region Constructors
/// <summary>
/// Creates a new command that can always execute.
/// </summary>
/// <param name="execute">The execution logic.</param>
public CommandHandler(Action<object> execute)
: this(execute, null)
{
}
/// <summary>
/// Creates a new command.
/// </summary>
/// <param name="execute">The execution logic.</param>
/// <param name="canExecute">The execution status logic.</param>
public CommandHandler(Action<object> execute, Predicate<object> canExecute)
{
if (execute == null)
throw new ArgumentNullException("execute");
_execute = execute;
_canExecute = canExecute;
}
#endregion // Constructors
[DebuggerStepThrough]
public bool CanExecute(object parameters)
{
// return _canExecute;
return _canExecute == null ? true : _canExecute(parameters);
}
// public event EventHandler CanExecuteChanged;
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public void Execute(object parameters)
{
_execute(parameters);
}
}
My XAML is as follows:
<DataGrid Name="results_grid" IsReadOnly="True" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto" Margin="10" ItemsSource="{Binding AllResults}" DisplayMemberPath="AllResultsGrid" ColumnWidth="100" RowHeight="30">
My Model Class:
public class AllResultsModel
{
private DataTable _allresultsgrid;
public DataTable AllResultsGrid
{
get { return _allresultsgrid; }
set { _allresultsgrid = value; }
}
}
Am I missing anything here? The code is getting built successfully and the data is retrieved from DB. But I m not able to view it in Datagrid.
I looks like you are missing the propertychanged() call.
I am pretty sure that the data table does not fire any property changed events.
try calling propertychanged on the "AllResults" property once you finished loading the data to it.
Your code is very confused and I think you need to learn well how to use MVVM : https://www.tutorialspoint.com/mvvm/ (download the PDF).
In your Model.cs you need to define only your classes that defines your objects like below:
public class MyData
{
public int Par1{ get; set; }
public string Par2 { get; set; }
public string Par3 { get; set; }
}
Then you need to create an observable collection in your ViewModel implementing NotifiyPropertyChanged:
public class ViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
private ObservableCollection<MyData> myData = ObservableCollection<MyData>;
public ObservableCollection<MyData> MyData
{
get { return myData; }
set { myData = value; NotifyPropertyChanged("MyData"); }
}
}
Then in the ViewModel you will execute the MyAction() function like this:
public void MyAction(ComboBoxViewModel cvm)
{
//Connecting to DB to retrieve data in datatable
MyData = new ObservableCollection<MyData>(dataFromDB);
}
Finally you simply binding MyData in the ItemsSource in the xaml.
Remember to assign your viewmodel like page/windows datacontext!
I am trying to attach a command and a commandparameter to a textbox on return key but without success. The parameter is the current text in the same textbox.
<TextBox x:Name="txtSearch">
<TextBox.InputBindings>
<KeyBinding Command="{Binding SearchCommand}"
CommandParameter="{Binding Path=Text, ElementName=txtSearch}" Key="Return" />
</TextBox.InputBindings>
</TextBox>
Basically I want to execute the command when user clicks on return/enter key and pass as a parameter the current text in the textbox.
I have found this link where it is said that in .NET 3.5 command parameter for keybinding is not accepting bindings. So a solution is proposed by code in code-behind but how can I pass a parameter to the command from the code?
First, you'll need to add the KeyBinding to your TextBox and set its Command on code-behind. Just add this in the constructor of your View:
public MainWindow()
{
InitializeComponent();
DataContext = new MyViewModel();
KeyBinding kb = new KeyBinding();
kb.Command = (DataContext as MyViewModel).SearchCommand;
kb.Key = Key.Enter;
txtSearch.InputBindings.Add(kb);
}
Then, you can bind the Text property of the TextBox named txtSearch to a property of your ViewModel. This way you don't need to pass a parameter as you can use the value of that property in your ViewModel inside the code that executes your Command.
Your ViewModel should look like this:
public class MyViewModel : ObservableObject
{
private string _txtSearch;
public string TxtSearch
{
get { return _txtSearch; }
set
{
if (value != _txtSearch)
{
_txtSearch = value;
OnPropertyChanged("TxtSearch");
}
}
}
private ICommand _searchCommand;
public ICommand SearchCommand
{
get
{
if (_searchCommand == null)
{
_searchCommand = new RelayCommand(p => canSearch(), p => search());
}
return _searchCommand;
}
}
private bool canSearch()
{
//implement canExecute logic.
}
private void search()
{
string text = TxtSearch; //here you'll have the string that represents the text of the TextBox txtSearch
//DoSomething
}
}
If you have access to C# 6 (Visual Studio 2015 and later versions), you can alter the call to the OnPropertyChanged to: OnPropertyChanged(nameof(TxtSearch));. This way you get rid of the "magic string" and eventual renaming of the property won't cause any problem for you.
And then your XAML should look like this: (Notice that you need to specify that te UpdateSourceTrigger must be PropertyChanged, so that your TxtSearch property of your ViewModel stays up to date when you hit the Enter key on your TextBox.
<TextBox Text="{Binding TxtSearch, UpdateSourceTrigger=PropertyChanged}" x:Name="txtSearch"/>
Your ViewModel needs to implement INotifyPropertyChanged and you need a proper ICommand implementation. Here I'll use the RelayCommand.
Those implementations are shown below.
Since your framework is .NET 3.5, implement it like this:
public class ObservableObject : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
This is a implementation of the RelayCommand:
public class RelayCommand : ICommand
{
private Predicate<object> _canExecute;
private Action<object> _execute;
public RelayCommand(Predicate<object> canExecute, Action<object> execute)
{
_canExecute = canExecute;
_execute = execute;
}
public bool CanExecute(object parameter)
{
return _canExecute(parameter);
}
public void Execute(object parameter)
{
_execute(parameter);
}
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
}
Ok I'll make this very simple! Here are viewmodels :
public class ObjectsModel
{
public event PropertyChangedEventHandler PropertyChanged = delegate { };
private string _objectName;
public string ObjectName
{
get
{
return _objectName;
}
set
{
if (value != _objectName)
{
_objectName = value;
PropertyChanged(this, new PropertyChangedEventArgs("ObjectName"));
}
}
}
public IEnumerable<Object> Objects {get;set;}
public ICommand AddCommand { get; private set; }
public ICommand SaveChangesCommand { get; private set; }
myDomainContext context = new myDomainContext();
public ObjectsModel()
{
objects = context.Objects;
context.Load(context.GetObjectsQuery());
}
}
public class InventoryModel
{
public event PropertyChangedEventHandler PropertyChanged = delegate { };
public IEnumerable<Inventory> Inventories {get;set;}
public ICommand AddCommand { get; private set; }
public ICommand SaveChangesCommand { get; private set; }
myDomainContext context = new myDomainContext();
public ObjectsModel()
{
objects = context.Objects;
context.Load(context.GetObjectsQuery());
}
}
So what I'm trying to do is in my second form where I want to add an inventory for an object, I have to select the object in a combobox. The question is, how do I fill my combobox? Create another instance of the "ObjectsModel" in the InventoryModel? or use another "context" where I would query the other table? Or is there an easier Xaml approach? If I'm not clear, tell me I'll put more examples/code.
tx a lot!
You want to bind the contents of the combobox to a list of items provided by your ViewModel and bind the selected item to another property on the same ViewModel.
Please get into the habit of naming actual view models to end in "ViewModel", rather than "Model", so they do not clash with your other "real" models. It actually looks like you are binding directly to your business models instead of ViewModels (which is not good).
I would like that my UIElement control acts like a LinkButton in ASP.Net when clicked, and sends an CommandArgument on MouseLeftButtonUp. I suppose I need to make a custom event for this, so I created a OnCommand event like this:
public delegate void OnCommand(object sender, CommandEventArgs e);
public class CommandEventArgs : EventArgs
{
public string CommandArgument { get; set; }
}
How can I add this event to MouseLeftButtonUp on my UIElement, and also pass the CommandArgument? Or is there another way to accomplish the effect of a LinkButton?
I didnt figure out a solution with custom events, so I made a UserControl instead, with a CommandArgument and CommandName properties.
public partial class LinkButton : UserControl
{
public string CommandArgument { get; set; }
public string CommandName { get; set; }
public LinkButton()
{
InitializeComponent();
CommandArgument = String.Empty;
CommandName = String.Empty;
}
public void AddElemnent(UIElement obj)
{
LayoutRoot.Children.Add(obj);
}
}