How can I refresh the UI in MVVM WPF - wpf

Question

My project is based on the MVVM pattern.
I have built a tree view that shows my file system.
Each folder has a checkbox for selecting the current folder.
The selection process is taking some time so, while the operation runs, there is a button which is disabled and at the end of the operation I`m enabling the button.
My problem is that when the button gets "disabled" I see it immediately. However, when the button is going back to the enabled mode I must do some action (like mouse click) to see the button enabled.
How can I make sure that the UI will be updated immediately after the button is enabled?
These are my buttons:
<Button Content="<- Back" Margin="5,0,5,0" Width="80" Height="25"
IsEnabled="{Binding CanMoveToPreviousPage, UpdateSourceTrigger=PropertyChanged}"
Command="{Binding Path=NavigateBackCommand, IsAsync=True}" />
<Button Content="{Binding ButtonNextCaption}" Margin="5,0,5,0" Width="80" Height="25"
IsEnabled="{Binding CanMoveToNextPage, UpdateSourceTrigger=PropertyChanged}"
Command="{Binding Path=NavigateNextCommand, IsAsync=True}" />
In my ViewModel I added this code:
public bool CanMoveToNextPage
{
get
{
return this.CurrentPage != null && this.CurrentPage.CanMoveNext;
}
set
{
if (CurrentPage != null)
{
this.CurrentPage.CanMoveNext = value;
OnPropertyChanged("CanMoveToNextPage");
}
}
}
public bool CanMoveToPreviousPage
{
get { return 0 < this.CurrentPageIndex && CurrentPage.CanMoveBack; }
set
{
if (CurrentPage != null)
{
this.CurrentPage.CanMoveBack = value;
OnPropertyChanged("CanMoveToPreviousPage");
}
}
}
The UI update happens just after I execute a mouse click or any keystroke.
This is the code of the action that is disabling and enabling the buttons:
void bg_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e)
{
DecrementDoneCounter();
if (ThreadSafeCouner == 0)//means all bg workers are done
{
UIlimitation(true);
}
}
private int ThreadSafeCouner; // check how many bgworkers run
public void IncrementDoneCounter() { Interlocked.Increment(ref ThreadSafeCouner); }
public void DecrementDoneCounter() { Interlocked.Decrement(ref ThreadSafeCouner); }
void bg_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
{
IncrementDoneCounter();
UIlimitation(false);
((bgArguments)e.Argument).SelectedDirectory.CanSelected = false;
MarkItems(((bgArguments)e.Argument).SelectedDirectory, ((bgArguments)e.Argument).IsSelect);
((bgArguments)e.Argument).FreeWorkerAllocation();
((bgArguments)e.Argument).SelectedDirectory.CanSelected = true;
}
//this is the enabling action which execute the propeties setters at the upper part of this post
private static void UIlimitation(bool limit)
{
MainWindowViewModel.Instance.CanMoveToNextPage = limit;
MainWindowViewModel.Instance.CanMoveToPreviousPage = limit;
}
What can I do?

Answer 1

You can adjust on your control Binding mode TwoWay and define triggers with PropertyChanged
{Binding ElementName=.., Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}

Answer 2

OK I found a solution.
I tried everything without success and eventually I found this thread:
Refresh WPF Command
I have used CommandManager.InvalidateRequerySuggested()
And its works.
Thanks for your help

Answer 3

Here's a code example of how you might set up your ViewModel with the INotifyPropertyChanged method of sending messages to update the UI:
public class MyViewModel : INotifyPropertyChanged
{
/******************************************************/
/* Property that you have created two-way binding for */
/******************************************************/
private double _myProperty
public double MyProperty
{
get { return _myProperty; }
set
{
_myProperty = value;
OnNotifyPropertyChanged("MyProperty");
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
protected void OnNotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
#endregion INotifyPropertyChanged Members
}