Interface IViewModel

A base view model interface for the gorgon editor.

Inherited Members

INotifyPropertyChanged.PropertyChanged

INotifyPropertyChanging.PropertyChanging

Namespace: Gorgon.Editor.UI

Assembly: Gorgon.Editor.API.dll

Syntax

public interface IViewModel : INotifyPropertyChanged, INotifyPropertyChanging

Remarks

This is the base class for all view models used by the editor and provides the bare minimum in functionality. This object already implements the INotifyPropertyChanged and the INotifyPropertyChanging interfaces to allow communication with a view.

When implementing a view model, the developers should set up their properties like this:

public ReturnType PropertyName
{
    get => _backingStoreValue;
    set
    {
        // Always check to see if the value has changed. This keeps the view model from being too "chatty" with the UI.
        if (_backingStoreValue == value)
        {
            return;
        }
    // Notify that the property is about to change. This allows the view to do any necessary clean up prior to updating the visual side.
    OnPropertyChanging();
    _backingStoreValue = value;
    // Now, notify that the property has changed. The view will intercept the change and update the visual associated with the property.
    OnPropertyChanged();
}

}

This setup notifies the view that the property has been updated, and that any associated visual should probably update as well. This is the most common pattern to use, however there will be times when a property notification is required from a method. If that is the case, the NotifyPropertyChanged(string), and NotifyPropertyChanging(string) methods should be used like this:

// This could be a callback function for an IEditorCommand<T> object.
private void DoCommandAction()
{
    NotifyPropertyChanging(nameof(ReadOnlyValue));
    _readOnlyValue++;
    NotifyPropertyChanged(nameof(ReadOnlyValue));
}

The difference being that for properties, you do not need to specify the name of the property being updated (the compiler figures it out), and in methods you do.

The view model is also equipped with several events that are used to notify the application that a long running operation is executing. Applications can intercept these events and display a progress panel, or "please wait" panel. These should only be used with asynchronous operations as they will not update correctly if everything is running on the same thread.

Methods

Load()

Function called when the associated view is loaded.

Declaration

void Load()

NotifyAllPropertiesChanged()

Function to notify that all properties on this type have changed their values.

Declaration

void NotifyAllPropertiesChanged()

NotifyAllPropertiesChanging()

Function to notify that all properties on this type are changing their values.

Declaration

void NotifyAllPropertiesChanging()

NotifyPropertyChanged(string)

Function to notify when a property has been changed.

Declaration

void NotifyPropertyChanged(string propertyName)

Parameters

Type	Name	Description
string	propertyName	Name of the property to change.

Remarks

This method used to notify when a property has changed outside of the property setter, or if a property other than the current property has changed inside of a property setter. The user can specify the name of the property manually through the propertyName parameter.

NotifyPropertyChanging(string)

Function to notify before a property is changed.

Declaration

void NotifyPropertyChanging(string propertyName)

Parameters

Type	Name	Description
string	propertyName	Name of the property to change.

Remarks

This method is used to notify before a property is changed outside of the property setter, or if a property other than the current property is changing inside of a property setter. The user can specify the name of the property manually through the propertyName parameter.

Unload()

Function called when the associated view is unloaded.

Declaration

void Unload()

Events

ProgressDeactivated

Event triggered when the progress overlay should be deactivated.

Declaration

event EventHandler ProgressDeactivated

Event Type

Type	Description
EventHandler

ProgressUpdated

Event triggered when the progress overlay panel over needs to be updated.

Declaration

event EventHandler<ProgressPanelUpdateArgs> ProgressUpdated

Event Type

Type	Description
EventHandler<ProgressPanelUpdateArgs>

WaitPanelActivated

Event triggered when a wait overlay panel needs to be activated.

Declaration

event EventHandler<WaitPanelActivateArgs> WaitPanelActivated

Event Type

Type	Description
EventHandler<WaitPanelActivateArgs>

WaitPanelDeactivated

Event triggered when a wait overlay panel needs to be deactivated.

Declaration

event EventHandler WaitPanelDeactivated

Event Type

Type	Description
EventHandler

Extension Methods

GorgonDebugExtensions.ValidateObject<T>(T, string)

GorgonNullExtensions.AsNullable<T>(object)

GorgonNullExtensions.IfNull<T>(object, T)

GorgonNullExtensions.IsNull(object)