TabControl Command binding

Question

I am using this code following code taken from Stackoverflow.

I want to transfer a string from one view model to another one on SelectionChanged event. But when I click on Tab2, I get Tab2 message box, but when I click on Tab1, I get both the message boxes indicating that both are getting executed. The same when I click Tab1, both message boxes are seen.

MainView.xaml

<TabControl>
 <TabItem Header="My tab 1" Selector.IsSelected="{Binding IsMyTab1Selected}"> ... </TabItem>
 <TabItem Header="My tab 2" Selector.IsSelected="{Binding IsMyTab2Selected}"> ... </TabItem>
</TabControl>

MainViewModel.cs

public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName) {
 PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}

public MainViewModel() {
 PropertyChanged += handlePropertyChanged;
}

public bool IsMyTab1Selected {
 get { return _IsMyTab1Selected ; }
 set {
  if (value != _IsMyTab1Selected ) {
   _IsMyTab1Selected = value;
   OnPropertyChanged("IsMyTab1Selected ");
  }
 }
}
private bool _IsMyTab1Selected = false;

public bool IsMyTab2Selected {
 get { return _IsMyTab2Selected ; }
 set {
  if (value != _IsMyTab2Selected ) {
   _IsMyTab2Selected = value;
   OnPropertyChanged("IsMyTab2Selected ");
  }
 }
}
private bool _IsMyTab2Selected = false;

private void handlePropertyChanged(object sender, PropertyChangedEventArgs e) {
 if (e.PropertyName == "IsMyTab1Selected") {
   MessageBox.Show("Tab_1 Clicked!");
 } else if (e.PropertyName == "IsMyTab2Selected") {
   MessageBox.Show("Tab_2 Clicked!");
 }
}

I am not able to get the mutually exclusiveness, point me where I am wrong.

you can not expect people to go through a multiple pages long link. add a minimal code example in your question. otherwise it is hard to help you. And why is there commented out code? — Welcor, May 25 '20 at 18:06
@Blechdose got it, so I posted the code taken from: https://stackoverflow.com/a/46074186 — highlander141, May 26 '20 at 02:52
@highlander141: When the first tab's `IsSelected` property is set to true, the second one's is set to false and vice versa. This is the expected behaviour, isn't it? Or what is your issue? — mm8, May 26 '20 at 10:07
yes even I thought the same. But both the message boxes are getting executed. As Gaz has said in his answer, 'e.NewValue' also has to be checked.. — highlander141, May 26 '20 at 10:17

Welcor · Accepted Answer · 2020-05-26T18:07:56.763

Option 1

you can change the setters to only call OnPropertyChanged(..) when the value is true:

public bool IsMyTab1Selected
{
    get { return _IsMyTab1Selected; }
    set
    {
        if (value != _IsMyTab1Selected)
        {
            _IsMyTab1Selected = value;
            if (_IsMyTab1Selected)
                OnPropertyChanged("IsMyTab1Selected");
        }
    }
}

public bool IsMyTab2Selected
{
    get { return _IsMyTab2Selected; }
    set
    {
        if (value != _IsMyTab2Selected)
        {
            _IsMyTab2Selected = value;
            if(_IsMyTab2Selected)
                OnPropertyChanged("IsMyTab2Selected");
        }
    }
}

Option 2

Or you can check in your handlePropertyChange() if the value is true like this

private void handlePropertyChanged(object sender, PropertyChangedEventArgs e)
{
    if (e.PropertyName == "IsMyTab1Selected")
    {
        if(IsMyTab1Selected)
            MessageBox.Show("Tab_1 Clicked!");
    }
    else if (e.PropertyName == "IsMyTab2Selected")
    {
        if(IsMyTab2Selected)
            MessageBox.Show("Tab_2 Clicked!");
    }
}

score 0 · Answer 2 · answered May 26 '20 at 08:23

0

The bindings will update on deselection too. You need to check e.NewValue in your handler, or why not simply check _IsMyTab1Selected etc?

answered May 26 '20 at 08:23

GazTheDestroyer

20,722
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I wanted to communicate from this ViewModel to another using RelayCommand, so I cannot check in xaml.cs code.. – highlander141 May 26 '20 at 08:47

TabControl Command binding

2 Answers2

Option 1

Option 2