[SOLVED] MVVM: command and canExecute flag

I'm working with my first command with a dynamic flag canExecute.

I have my save command, that it must enabled only when user makes some data changes.

I was thinking about binding an action when the mods are made, but I get errors, maybe this isn't the right way.

This is my xaml (as you can see, all my fields are in a layout control):

            <dxlc:LayoutGroup Header="Configurazione tecnica" View="GroupBox" Orientation="Vertical">
                <dxlc:LayoutItem Label="Tipo sistema">
                    <dxe:ComboBoxEdit IsTextEditable="False" EditValue="{Binding IDTTS}" ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}},Path=DataContext.tts}"  />
                </dxlc:LayoutItem>
                <dxlc:LayoutItem Label="Locazione">
                    <!--<dxe:ComboBoxEdit  EditValue="{Binding REMOTO}" ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}},Path=DataContext.locations}"  />-->
                    <StackPanel Margin="0" Orientation="Horizontal" VerticalAlignment="Center" HorizontalAlignment="Left">
                        <RadioButton x:Name="rd_LOCALE" Content="{DynamicResource Locale}" Margin="10,0,0,0" VerticalAlignment="Center" GroupName="Location" IsChecked="True" Panel.ZIndex="9" TabIndex="10" />
                        <RadioButton Content="{DynamicResource Remoto}" Margin="10,0,6,0" x:Name="rd_REMOTO" Tag="PRISMA" VerticalAlignment="Center" IsChecked="{Binding REMOTO}" GroupName="Location" Panel.ZIndex="10" TabIndex="11" />
                    </StackPanel>
                </dxlc:LayoutItem>
                <dxlc:LayoutItem Label="Tipo di connessione">
                    <!--<dxe:ComboBoxEdit  EditValue="{Binding TIPOCONN}" />-->
                    <StackPanel Margin="0" Orientation="Horizontal" VerticalAlignment="Center">
                        <RadioButton Content="{DynamicResource Terminale}" Margin="10,0,0,0" x:Name="rd_TIPOCONN" Tag="PRISMA" VerticalAlignment="Center" GroupName="TipoConn" IsChecked="True" Panel.ZIndex="11" TabIndex="12" />
                        <RadioButton x:Name="rd_SLAVE" Content="Slave" Margin="10,0,6,0" Tag="PRISMA" VerticalAlignment="Center" IsChecked="{Binding TIPOCONN}" GroupName="TipoConn" Panel.ZIndex="12" TabIndex="13" />
                    </StackPanel>
                </dxlc:LayoutItem>
            </dxlc:LayoutGroup>

            <dxlc:LayoutGroup Header="Centralina STK" View="GroupBox" Orientation="Vertical">
                <dxlc:LayoutItem >
                    <!--<dxe:ComboBoxEdit  EditValue="{Binding SERMATIC}" />-->
                    <StackPanel DockPanel.Dock="Top" Orientation="Horizontal" HorizontalAlignment="Center" Margin="0,6">
                        <RadioButton x:Name="rd_sermatic" Content="{DynamicResource SI}" Margin="10,0,0,0"  Tag="PRISMA" VerticalAlignment="Center" Width="100" HorizontalAlignment="Left" IsChecked="{Binding SERMATIC}" GroupName="stk" Panel.ZIndex="13" TabIndex="14" />
                        <RadioButton x:Name="rd_sermaticNO" Content="{DynamicResource NO}" Margin="10,0,0,0" Tag="PRISMA" VerticalAlignment="Center" Width="100" HorizontalAlignment="Left" GroupName="stk" IsChecked="True" Panel.ZIndex="14" TabIndex="15" />
                    </StackPanel>
                </dxlc:LayoutItem>
                <dxlc:LayoutItem >
                    <!--<dxe:ComboBoxEdit  EditValue="{Binding SERMATICCOM}"/>-->
                    <UniformGrid Rows="1" Columns="2" DockPanel.Dock="Top" Margin="4,0,4,4" IsEnabled="{Binding IsChecked, ElementName=rd_sermatic}">
                        <TextBlock Margin="0" TextWrapping="Wrap" Text="{DynamicResource PortaCOM}" TextAlignment="Right" VerticalAlignment="Center" HorizontalAlignment="Right"/>
                        <ComboBox x:Name="cmb_SERMATICCOM" Height="23" Margin="10,2,0,0" Panel.ZIndex="15" TabIndex="16">
                            <ComboBoxItem Content="----" />
                            <ComboBoxItem Content="COM1" />
                            <ComboBoxItem Content="COM2" />
                            <ComboBoxItem Content="COM3" />
                            <ComboBoxItem Content="COM4" />
                            <ComboBoxItem Content="COM5" />
                            <ComboBoxItem Content="COM6" />
                            <ComboBoxItem Content="COM7" />
                            <ComboBoxItem Content="COM8" />
                        </ComboBox>
                    </UniformGrid>
                </dxlc:LayoutItem>
            </dxlc:LayoutGroup>
        </dxlc:LayoutControl>

And this is my MainWindowVIewModel, where I define the command and the canExceute:

private bool CanSave()
{
    return SaveButtonEnabled;
}

public ICommand SaveCommand { get; private set; }

void EnableSave(NotifyCollectionChangedEventArgs e)
{
    if (e.Action == NotifyCollectionChangedAction.Replace)
        SaveButtonEnabled = true;
}

private bool p_saveButtonEnabled=false;
public bool SaveButtonEnabled
{
    get{ return p_saveButtonEnabled; }
    set
        {
        p_saveButtonEnabled = value;
        base.RaisePropertyChangedEvent("SaveButtonEnabled");
    }
}

private void SaveData()
{
    MainWindow.dbContext.SaveChanges();
    SaveButtonEnabled = false;
    //base.RaisePropertyChangedEvent("SaveButtonEnabled");
}

And when I populated my observableColletion, where I change data in the binded user control, I have:

ListaImpianti.CollectionChanged += (s, e) => EnableSave(e);

ListaImpianti is binded to the xaml in this way:

<DockPanel Grid.Row="1" Margin="0,60,0,0">
    <dxg:GridControl x:Name="lst1" ItemsSource="{Binding ListaImpianti}"  EnableSmartColumnsGeneration="True" FilterCriteria="{Binding FilterCriteria, ElementName=searchControl}"  MaxHeight="500" Height="266" VerticalAlignment="Top" Margin="0,-27,0,0" Width="332" ShowBorder="False">
        <dxg:GridControl.Columns>
            <dxg:GridColumn x:Name="CODICE" Binding="{Binding CODICE}" FieldName="CODICE"/>
            <dxg:GridColumn x:Name="NOME" Binding="{Binding NOME}" FieldName="NOME"/>
        </dxg:GridControl.Columns>
        <dxg:GridControl.View>
            <dxg:TableView AllowPerPixelScrolling="True" AllowEditing="False" ShowGroupPanel="False" ShowFilterPanelMode="Never"  />
        </dxg:GridControl.View>
     </dxg:GridControl>
</DockPanel>

ListaImpianti is defined as:

 public ObservableCollection<TabImpianti> ListaImpianti
 {
    get { return p_ListaImpianti; }
    set
    {
        p_ListaImpianti = value;
        base.RaisePropertyChangedEvent("ListaImpianti");
    }
}
[...]
p_ListaImpianti = new ObservableCollection<TabImpianti>();
var query2 = (from r in MainWindow.dbContext.TabImpianti select r);
foreach (TabImpianti ti in query2) { p_ListaImpianti.Add(ti); }

But enable save is never called.. why?

Piero