EventToCommand SelectionChanged in Combobox to pass parameter - silverlight

Question

I have a combobox with rules in a view and it works well, but I want another field of the model from the itemsource to be used to bind to (or as I used it) update another field score.
E.g. if you select rule 1 in the combobox it should update the score field in the view with 1 and if you change the selecteditem to rule 2 it should show 2 in the score field.
My code might be a bit crippled because I experimented 'on the way here' to achieve the desired result, I have a ScoreView with a datagrid which itemsource is scores:
SelectionChangedCommand = new RelayCommand<string>((_score) => SelectedRuleChanged(_score));
private void SelectedRuleChanged(string _score)
{
int _tmpint;
_tmpint = this.SelectedScore.Model.score;
int.TryParse(_score, out _tmpint);
this.SelectedScore.Model.score = _tmpint;
//Todo weghalen lokale rules collectie en get_rules voids
//get_rules_by_ruleset(this.SelectedMatch.Model.ruleset);
}
<ComboBox
Height="23" HorizontalAlignment="Left"
Name="cmbRules" VerticalAlignment="Top" Width="100" ItemsSource="{Binding MatchVM.Rules}" SelectedValue="{Binding Model.ruleid, Mode=TwoWay}"
DisplayMemberPath="Model.name" SelectedValuePath="Model.ruleid">
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<cmd:EventToCommand Command="{Binding MainScore.SelectionChangedCommand, Mode=OneWay,
Source={StaticResource Locator}}" CommandParameter="{Binding Model.score}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
I try to pass the elements selecteditem (which I bound to model.score) as a command parameter..
Maybe I should use the selecteditem of MatchVMRule but the score text field is bound to the Scores ViewModel instead of the Rules ViewModel?
Thanks in advance,
Mike
UPDATE SOLVED
I finally solved it by creating two separate props rules collection and selected rule in my MainScoreViewModel.
I got rid of the eventocommand and handled the update of the score field in my Score Model based on the score of the Rule Model in the setter of the SelectedRule:
/// <summary>
/// Gets the SelectedRule property.
/// Changes to that property's value raise the PropertyChanged event.
/// </summary>
public RuleViewModel SelectedRule
{
get
{
return _selectedRule;
}
set
{
if (_selectedRule == value)
{
return;
}
_selectedRule = value;
this.SelectedScore.Model.score = this.SelectedRule.Model.score;
RaisePropertyChanged(SelectedRulePropertyName);
}
}
<ComboBox
Height="23" HorizontalAlignment="Left"
Name="cmbRules" VerticalAlignment="Top" Width="100" ItemsSource="{Binding ScoreVM.Rules,
Mode=TwoWay}" SelectedValue="{Binding Model.ruleid, Mode=TwoWay}"
DisplayMemberPath="Model.name" SelectedValuePath="Model.ruleid" SelectedItem="{Binding
ScoreVM.SelectedRule, Mode=TwoWay}">
</ComboBox>

Answer 1

What about using the PropertyChange notification on your ViewModel to handle the SelectionChanged event instead of trying to handle it from the View?
public ParentViewModel()
{
this.Model.PropertyChanged += Model_PropertyChanged;
}
void Model_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
switch (e.PropertyName)
{
case "ruleid":
this.SelectedScore.Model.Score = Model.Score;
}
}