MVVM TabControl update ComboBox

Question

I'm rather new to MVVM as a concept and I'm currently trying to set things up so that changing the selected index of a TabControl will change the item source of a ComboBox I have. Currently I have things set up as follows:

    public int SelectedTabIndex
    {
        get
        {
            return _selectedTabIndex;
        }
        set
        {
            _selectedTabIndex = value;
            if (_selectedTabIndex == 0)
            {
                _readOnlyArray = ReadOnlyArrays.ReadOnlyColumnArrays.LoanerItemsSelect;
            }
            else if (_selectedTabIndex == 1)
            {
                _readOnlyArray = ReadOnlyArrays.ReadOnlyColumnArrays.CustomerSelect;
            }
            else if (_selectedTabIndex == 2)
            {
                _readOnlyArray = ReadOnlyArrays.ReadOnlyColumnArrays.JobSelect;
            }
        }

Which is bound to the following of a TabControl:

SelectedIndex="{Binding SelectedTabIndex, Mode=TwoWay}"

I also have this:

    public string[] ReadOnlyArray 
    {
        get { return _readOnlyArray; }

        set { _readOnlyArray = value;}
    }

Which is bound to a ComboBox as follows:

ItemsSource="{Binding readOnlyArray, Mode=TwoWay}"

I know most likely I'm doing this completely wrong but I'd like the ComboBox's item source to update whenever the tab index of the TabControl is changed.

Irrelevant question, why is the property called ReadOnlyArray when it defines a public setter? — PoweredByOrange
@programmer93 It's a terrible name. The ItemSource of the ComboBox is a ReadOnly Array. I named it somewhat hastily and plan to change it once things are working. — DanteTheEgregore

ghord ghord · Accepted Answer · 2013-06-21T16:57:26

You should notify the interface that ReadOnlyArray is changing after SelectedTabIndex changes. Assuming your view model implements INotifyPropertyChanged, you need to fire approppriate event hander:

    set
    {
        _selectedTabIndex = value;
        if (_selectedTabIndex == 0)
        {
            _readOnlyArray = ReadOnlyArrays.ReadOnlyColumnArrays.LoanerItemsSelect;
        }
        else if (_selectedTabIndex == 1)
        {
            _readOnlyArray = ReadOnlyArrays.ReadOnlyColumnArrays.CustomerSelect;
        }
        else if (_selectedTabIndex == 2)
        {
            _readOnlyArray = ReadOnlyArrays.ReadOnlyColumnArrays.JobSelect;
        }

        //Your helper method from base class calling          
        // INotifyPropertyChanged.PropertyChanged event
        this.RaisePropertyChanged("ReadOnlyArray");
    }

If it still doesn't work, check out VisualStudio output window for any binding errors.

MVVM TabControl update ComboBox

1 Answers