Defects of multi select of combobox

[Yang]

Hi team,

I know it might not be a popular topic about multi select of combobox here. I read a lot of previous threads about multiple select, and finally can make it satisfy my requirement.  However, there is a defect of my implementation. I would try my best to describe my problem as clear as i can.

 I have two comboboxes, say A and B. The items of B are depending on what's selected in A. When the App starts up, I select a item, then the items of B refreshes correctly, and i can also select items in B without problems. Now the defect comes, i unselect the item and select some other items, the items in B still can refresh correctly. But, when i select items in now this time, the selectionBox is not changing any more, with a blank always. I don't know what i've been missing.

 I am creating a repository in github here [e-mail]:hobbycamp/multicombobox.git. You guys can run it for real. Thanks for any help.

-Yang

[Nasko]

Hi Yang,

The observed by you behavior is caused by the clearing of the collection bound to the ComboBox's ItemsSource. When you clear it the SelectedIndex of the ComboBox is set to -1 and thus the DataContext of the "CheckableItemTemplate" becomes null. What we could suggest you is to bind the SelectedIndex property to a property inside your DataViewModel and when you clear the collection to set it back to 0 - thus everything should work as expected:

<telerik:RadComboBox x:Name="ComboBox2"
...
                    SelectedIndex="{Binding SelectedIndex, Mode=TwoWay}"
...>
</telerik:RadComboBox>

private int selectedIndex ;

public int SelectedIndex
{
    get
    {
        return this.selectedIndex;
    }

    set
    {
        if (this.selectedIndex != value)
        {
            this.selectedIndex = value;
            this.OnPropertyChanged(() => this.SelectedIndex);
        }
    }
}

private void OnItem1Checked(object sender, NotifyCollectionChangedEventArgs e)
{
    this.Item2Collection.Clear();
    this.SelectedIndex = 0;
...
}

We hope this will help you.

Regards,
Nasko
Telerik

[Yang]

Sorry for the late reply, quite busy for now. I am so sorry that your solution doesn't work. See my pull request: https://github.com/hobbycamp/multicombobox/pull/1/files to make sure i've updated the right place.

[Nasko]

Hi Yang,

It seems the proposed changes are made on the right place. The only difference is that inside the OnPropertyChanged you need to pass the property not the field as a parameter:

public int SelectedIndex2
{
    get
    {
        return this._selectedIndex2;
    }
    set
    {
        if(this._selectedIndex2 != value)
        {
            this._selectedIndex2 = value;
            this.OnPropertyChanged(() => this.SelectedIndex2);
        }
    }
}

Please, check the attached video that demonstrates how the proposed approach works on our side. I am also sending you your sample project with all the needed modifications made.

Hopes this helps.

Regards,
Nasko
Telerik

[Yang]

Awesome. It works now. Thank you very much.