Tap gesture event + Longlistselector + Groupheader tap

Question

I'm struggling with a problem which is: I have a LonglistSelector like this:

 <phone:LongListSelector Name="ListContacts" 
                                           ItemsSource="{Binding GroupedPeople}"
                                           JumpListStyle="{StaticResource LongListSelectorJumpListStyle}"                                             
                                           GroupHeaderTemplate="{StaticResource LongListSelectorGroupHeaderTemmplate}"
                                           ItemTemplate="{StaticResource LongListSelectorItemTemplate}"
                                           HideEmptyGroups ="True" IsGroupingEnabled ="true" LayoutMode="List">
                            <i:Interaction.Triggers>
                                <i:EventTrigger EventName="Tap">
                                    <mvvmlight:EventToCommand Command="{Binding ListContactsTapCommand, Mode=OneTime}" CommandParameter="{Binding ElementName=ListContacts, Path=SelectedItem}" />

                                </i:EventTrigger>
                            </i:Interaction.Triggers>
                        </phone:LongListSelector>

It is very similar to the PeopleHub in this link: http://code.msdn.microsoft.com/wpapps/PeopleHub-Windows-Phone-80-88abe94d

My problem is with the tap event. When I tap the first time in a letter all happens as expected. Then, I tap on a contact to see more information, and it's all good as well.

The problem happens when I click again on the letter, because the tap event is fired twice (I think): one because SelectedItem is not null and other to show the letter's.

In my ViewModel I have this:

 public RelayCommand<Contact> ListContactsTapCommand { get; private set; }

.....

 this.ListContactsTapCommand = new RelayCommand<Contact>(contact => ShowContactInformation(contact), contact => contact != null);

 private void ShowContactInformation(Contact c)
        {

            ServiceLocator.Current.GetInstance<ContactInfoViewModel>().ContactInfo = c;
            _navigationService.NavigateTo(new Uri(ViewModelLocator.ContactInfoPage, UriKind.Relative));

        }

What I think could be the solution is to reset SelectedItem or then a way to know where I'm tapping.

Can anyone give a hand? Thanks in advance.

Regards

Answer 1

Solved my problem in a way I don't fully agree...and it "breaks" mvvm pattern a little

This is what I've done

View:

<mvvmlight:EventToCommand Command="{Binding ListContactsTapCommand, Mode=OneTime}" CommandParameter="{Binding ElementName=ListContacts}"/>

ViewModel:

 this.ListContactsTapCommand = new RelayCommand<LongListSelector>(param => ShowContactInformation(param), param => param.SelectedItem != null);
 private void ShowContactInformation(LongListSelector c)
        {

            ServiceLocator.Current.GetInstance<ContactInfoViewModel>().ContactInfo = c.SelectedItem as Contact;
            _navigationService.NavigateTo(new Uri(ViewModelLocator.ContactInfoPage, UriKind.Relative));
            c.SelectedItem = null;

        }

The reason I don't agree this approach is because ViewModel will have to know objects from view...which is not supposed, but since LonglistSelector doesn't allow Binding to SelectedItem this was the solution I came with.

If any of you have any other point... I'll be glad to know it :)

Thanks again in advance.