I am having a problem with the kendo checkbox. It is not setting the value i check on it and sending to the controller. It is showing in the javascript model (in a custom save event) that the field is null. It also hits the model in the controller as null.
How i declare the field:
[NotMapped]
public bool? ValueBool { get; set; }
the control is in a partial view and is called like this:
#Html.Kendo().CheckBoxFor(m=> m.ValueBool).Checked(Convert.ToBoolean(Model?.Value ?? "false"))
This shows the control with the correct value.
However it's not passing the value when i click "save". Any ideas?
ValueBool is nullable, so, if you are going for a 'tri-state' checkbox, meaning if the user doesn't touch the field, it stays null, but if they check it, it's true, uncheck it, it's false, you'll need to look at something like this: https://stackoverflow.com/a/17822452/493557
However, since you're converting the nullable bool to an either True or False value, perhaps you aren't looking for that tri-state option and you can either change your ValueBool to not be nullable, or do something like the following:
In your model add a boolean property that returns a non-nullable representation of your underlying nullable boolean:
public bool ValueBoolNotNullable //Obviously rename this :)
{
get
{
return ValueBool.HasValue ? ValueBool.Value : false;
}
set
{
ValueBoolNotNullable = value
}
}
And update your view CheckBoxFor to use that new property:
#Html.Kendo().CheckBoxFor(m=> m.ValueBoolNotNullable)
Related
How do I know when is a value of any control changed by user input (interaction with mouse or keyboard)?
Any suggestions? Is there a common way for this?
EDIT:
I am seeking for attached property or extending already given controls or whatever is needed just to get notified whether user input is taking place at the time value is changed. eg ComboBox SelectedItem changed by user input (User could enter text or select an item in drop down menu)
Its pure View thing therefore I am sorry but no ViewModel solutions for this issue will be accepted.
The simplest way would simply be to register to the Binding.TargetUpdated event, which is fired when the UI-side is updated (while Binding.SourceUpdated is fired when the ViewModel-side is updated)
Use a property with backing field in your view model. Introduce a second setter - a SetProp() method - that you use inside your ViewModel. That way you can add different behavior, depending on the origin of the call.
```
private bool mMyProp;
public bool MyProp
{
get { return mMyProp; }
set
{
if (mMyProp != value)
{
mMyProp = value;
// Todo: add here code specific for calls coming from the UI
RaisePropertyChanged(() => MyProp);
}
}
}
public void SetPropFromViewModel(bool value)
{
if (mMyProp != value)
{
mMyProp = value;
// Todo: add here code specific for calls coming from ViewModel
RaisePropertyChanged(() => MyProp);
}
}
I have three classes,
first:
public class Setting
which has properties:
string ID, string Value; (implements INotifyPropertyChanged on Value)
Second:
public class SettingCollection
which is a:
ObservableCollection<Setting>
Third:
public class SimObject
which has properties:
string ID, SettingsCollection Settings;
I have a View:
SettingsDisplay.xaml
which has dependency property:
SettingsCollection SimObjSettings;
and displays the setting's ID and with its Value in a TextBox inside an ItemsContainer.
My MainWindow ViewModel has a SimObject Jeff; and in the View I have
<local:SettingsDisplay SimObjSettings="{Binding Jeff.Settings}"/>
This all works fine.
I need to know when a Setting Value changes and when that happens I need to know the SimObject ID the Setting belongs to so that I can call a method that sends an event with the Setting ID, Value and the SimObject ID. (e.g. SendEvent(settingID, settingValue, targetObject))
Obviously Setting's and SettingCollection's have no knowledge of what SimObject they belong to.
The way I've tried to do this is in the Setting class call SendEvent in the Value property's Setter.
I'm struggling to find a suitable way to pass the SimObject's ID down the chain to the Setting's class, I also don't think this is a good solution.
What is the best way to acheive what I'm trying to do?
There are lots of ways to do this, but obviously all of them involve someone observing the SettingsCollection and dynamically attaching/detaching PropertyChanged handlers to all items inside it (at least that's what your requirements sound to me).
I would argue that if all you want is unconditional live updetes you should not involve the Views and ViewModels at all in this. Simply write an implementation of something like this:
interface ISimObjLiveUpdateService
{
void StartObserving(SimObject o);
bool IsObserving(SimObject o);
bool StopObserving(SimObject o);
}
The actual implementation would hook up to observe o.SettingsCollection and all items in it. Before you display a SimObject you StartObserving it, and when the view is closed you StopObserving it.
I ended up solving this by giving all Setting's a SimObject property, which was the setting's SimObject owner, and creating an event handler delegate void SettingHandler(string settingID, string settingValue, string targetObj);
in SimObject : public event SettingHandler SettingChanged;
public void RaiseSettingChangedEvent(string settingId, string settingValue, string targetObj)
{
if (SettingChanged != null)
{
SettingChanged(settingId, settingValue, targetObj);
}
}
In Setting on the string Value Setter:
set
{
_value = value;
RaisePropertyChanged("Value");
SimObject.RaiseSettingChangedEvent(ID, Value, SimObject.Settings["UID"].Value);
}
Then in SettingsDisplay I created a SelectedPropertyChangedCallback which adds the ParameterChanged event to the SimObject and also contains the SettingChanged method:
public void SettingChanged(string settingID, string settingValue, string targetObj)
{
Framework.GetBusinessDelegate().SendEvent(settingID, settingValue, targetObj);
}
Don't know how to add syntax highlighting to make this answer clearer.
My issue is I have three properties with mutually dependent in my WPF application. I have implemented InotifyPropertyChanged also for the class. I am not sure how to update second property based on other.
Example:
Properties : ActualValue, ChangedValue, Change
ActualValue is Fixed, and it is possible to update ChangedValue and Change. That means if I update ChangedValue, the Change is calculated like (ActualValue-ChangedValue) and set. And when Change updates, the ChangedValue will be calculated based on ActualValue and Change.
You can put the logic inside the setters of properties that others depend on. Since it's a circular dependency, just make sure that inside the setters you change the private variable-- don't use the property setter, as that would create an infinite loop. Like this:
private string _change, _changedValue;
public string ChangedValue {
set {
_changedValue = value;
_change = ActualValue - _changedValue;
NotifyPropertyChanged("ChangedValue");
NotifyPropertyChanged("Change");
}
}
public string Change {
set {
_change = value;
_changedValue = ActualValue - _change;
NotifyPropertyChanged("Change");
NotifyPropertyChanged("ChangedValue");
}
}
I have a WPF view that displays a Shipment entity. I have a textblock that contains an asterisk which will alert a user that the record is changed but unsaved. I originally hoped to bind the visibility of this (with converter) to the Shipment.EntityState property.
If value = EntityState.Modified Then
Return Visibility.Visible
Else
Return Visibility.Collapsed
End If
The property gets updated just fine, but the view is ignorant of the change. What I need to know is, how can I get the UI to receive notification of the property change. If this cannot be done, is there a good way of writing my own IsDirty property that handles editing retractions (i.e. if I change the value of a property, then change it back to it's original it does not get counted as an edit, and state remains Unchanged).
Any help, as always, will be greatly appreciated.
Cory
After struggling with the same problem for a little bit, here is a solution that is working for me.
Lets say I have an entity called Trip that was generated by EF, I just needed to extend the class by means of partial class as showed below. The RaiseEntityStateChanged method is useful when you need to force a refresh of the EntytyState property, for example after calling the context's SaveChanges method.
partial class Trip
{
bool _forced = false;
System.Data.EntityState _lastState;
public Trip()
{
_lastState = EntityState;
this.PropertyChanged += (s, e) =>
{
if (_lastState != this.EntityState && e.PropertyName != "EntityState" || _forced)
{
_forced = false;
OnPropertyChanged("EntityState");
}
_lastState = this.EntityState;
};
}
public virtual void RaiseEntityStateChanged()
{
_forced = true;
OnPropertyChanged("EntityState");
}
}
I don't see a way to create a XAML binding on an existing property to do what you are trying to do. But you could write your own IsDirty property, based on the EntityState; you could update this value by subscribing to the PropertyChanged event raised by the base EntityObject. Of course, you'll need to also raise a PropertyChanged event for IsDirty (so that the GUI is notified) and ignore this event in your handler (to prevent infinite recursion).
Edit: added the following after question by OP:
This is how I see it, in order to answer the comment.
In the shipment class, one can add:
public bool IsDirty { get { return EntityState == EntityState.Modified; } }
public Shipment() {
...
PropertyChanged += OnShipmentChanged;
}
private void OnShipmentChanged(object sender, PropertyChangedEventArgs pcea) {
if (pcea.PropertyName != "IsDirty") { // prevent recursion
OnPropertyChanged("IsDirty"); // notifies binding listener that the state has changed
}
}
During the night, I thought of another way, which is to create a multi-binding on each Shipment property (which would replace this whole notion of an IsDirty property and would actually answer the original question). This could make sense if there are just a couple of Shipment properties. I'd say if there are more than 3, we should forget about this idea.
I have a ComboBox that has the SelectedItem bound to the ViewModel.
<ComboBox SelectedItem="{Binding SelItem, Mode=TwoWay}" ItemsSource="{Binding MyItems}">
When the user selects a new Item in the View ComboBox, I want to display a prompt and verify that they want to make the change.
In the SetItem Property setter in the View Model, I display a Dialog to confirm the selection. When they say yes, it works fine.
My problem is, when the user clicks on "No" I am not sure who to get the ComboBox
to revert back to the previous value. The Property in the ViewModel has the correct
older value, however in the View the ComboBox displays the newly Selected Value.
I want the user to select an item, confirm they want to go ahead with it, and if they
decide not to, I want the ComboBox to revert back to the previous item.
How can I accomplish this?
Thanks!
When the user says "no", WPF is unaware that the value has changed. As far as WPF is concerned, the value is whatever the user selected.
You might try raising a property changed notification:
public object SelItem
{
get { ... }
set
{
if (!CancelChange())
{
this.selItem = value;
}
OnPropertyChanged("SelItem");
}
}
The problem is, the change notification happens within the same context of the selection event. Thus, WPF ignores it because it already knows the property has changed - to the item the user selected!
What you need to do is raise the notification event in a separate message:
public object SelItem
{
get { ... }
set
{
if (CancelChange())
{
Dispatcher.BeginInvoke((ThreadStart)delegate
{
OnPropertyChanged("SelItem");
});
return;
}
this.selItem = value;
OnPropertyChanged("SelItem");
}
}
WPF will then process this message after it's done processing the selection changed event and will therefore revert the value in the view back to what it should be.
Your VM will obviously need access to the current Dispatcher. See my blog post on a base VM class if you need some pointers on how to do this.
Thanks for this question and answers. The Dispatcher.BeginInvoke helped me and was part of my final solution, but the above solution didn't quite work in my WPF 4 app.
I put together a small sample to figure out why. I had to add code that actually changed the underlying member variable's value temporarily so that when WPF re-queried the getter, it would see that the value chaned. Otherwise, the UI didn't properly reflect the cancellation and the BeginInvoke() call did not do anything.
Here's a my blog post with my sample showing a non-working and a working implementation.
My setter ended up looking like this:
private Person _CurrentPersonCancellable;
public Person CurrentPersonCancellable
{
get
{
Debug.WriteLine("Getting CurrentPersonCancellable.");
return _CurrentPersonCancellable;
}
set
{
// Store the current value so that we can
// change it back if needed.
var origValue = _CurrentPersonCancellable;
// If the value hasn't changed, don't do anything.
if (value == _CurrentPersonCancellable)
return;
// Note that we actually change the value for now.
// This is necessary because WPF seems to query the
// value after the change. The combo box
// likes to know that the value did change.
_CurrentPersonCancellable = value;
if (
MessageBox.Show(
"Allow change of selected item?",
"Continue",
MessageBoxButton.YesNo
) != MessageBoxResult.Yes
)
{
Debug.WriteLine("Selection Cancelled.");
// change the value back, but do so after the
// UI has finished it's current context operation.
Application.Current.Dispatcher.BeginInvoke(
new Action(() =>
{
Debug.WriteLine(
"Dispatcher BeginInvoke " +
"Setting CurrentPersonCancellable."
);
// Do this against the underlying value so
// that we don't invoke the cancellation question again.
_CurrentPersonCancellable = origValue;
OnPropertyChanged("CurrentPersonCancellable");
}),
DispatcherPriority.ContextIdle,
null
);
// Exit early.
return;
}
// Normal path. Selection applied.
// Raise PropertyChanged on the field.
Debug.WriteLine("Selection applied.");
OnPropertyChanged("CurrentPersonCancellable");
}
}
Another way to do it (make sure you also read the comments):
http://amazedsaint.blogspot.com/2008/06/wpf-combo-box-cancelling-selection.html
From the link:
Another solution for issue of recursive calling of event handler without global variable is to cancel handler assignment before programmatic selection change, and reassign it after that.
Ex:
cmb.SelectionChanged -= ComboBox_SelectionChanged;
cmb.SelectedValue = oldSel.Key;
cmb.SelectionChanged += ComboBox_SelectionChanged;
My way of doing it is to let the change go through and perform validation in a lambda that is BeginInvoked in the Dispatcher.
public ObservableCollection<string> Items { get; set; }
private string _selectedItem;
private string _oldSelectedItem;
public string SelectedItem
{
get { return _selectedItem; }
set {
_oldSelectedItem = _selectedItem;
_selectedItem = value;
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("SelectedItem"));
}
Dispatcher.BeginInvoke(new Action(Validate));
}
}
private void Validate()
{
if (SelectedItem == "Item 5")
{
if (MessageBox.Show("Keep 5?", "Title", MessageBoxButton.YesNo) == MessageBoxResult.No)
{
SelectedItem = _oldSelectedItem;
}
}
}
or in your ViewModel:
Synchronization.Current.Post(new SendOrPostCallback(Validate), null);