wpf toolkit data grid - wpf

Question

hello i'm building a wpf app with data grids,
the pattern is model view view model.
all og my screens contains a contentcontrol, and i just assign him the view model, that have a suitable data template,
anyway, my problem is with combo box column, the data context is the presented entity, and i need it to be the view model.
whats the best solution?

Answer 1

I'm using another datagrid, but it might be similar. The way i did it was like that:
in the XAML, i defined an ObjectDataProvider in the resources:
<ObjectDataProvider x:Key="VM" ObjectInstance="{x:Null}" x:Name="vm"/>
then after assigning the DataContext (either the constructor or the DataContextChanged event), i did this:
(this.Resources["VM"] as ObjectDataProvider).ObjectInstance = this.DataContext;
In the Combobox xaml, i used that as binding source:
ItemsSource="{Binding Source={StaticResource VM}, Path=SomeItems, Mode=OneWay}"
Not sure if it works for the microsoft datagrid, but i guess it's worth a try.

Answer 2

this is how I used ViewModel with ComboBoxes, the DataContext is the ViewModel, not the underlying entity (List<Person>).
ViewModel (Person is a Simple class with Name and Age):
public class PeopleViewModel : INotifyPropertyChanged
{
private List<Person> _peopleList;
private Person _selectedPerson;
public PeopleViewModel()
{
// initialize with sample data
_peopleList = getPeopleList();
}
// gets sample data
private List<Person> getPeopleList()
{
var result = new List<Person>();
for (int i = 0; i < 10; i++)
{
result.Add(new Person("person " + i, i));
}
return result;
}
public List<Person> PeopleList
{
get { return _peopleList; }
}
public Person SelectedPerson
{
get { return _selectedPerson; }
set
{
if (_selectedPerson == value) return;
_selectedPerson = value;
// required so that View know about changes
OnPropertyChanged("SelectedPerson");
}
}
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
// WPF will listen on this event for changes
public event PropertyChangedEventHandler PropertyChanged;
}
XAML for ComboBox:
<ComboBox Name="cmbEnum" Width="150" ItemsSource="{Binding Path=PeopleList}" SelectedValue="{Binding Path=SelectedPerson}" SelectedValuePath="" DisplayMemberPath="Name" ></ComboBox>
And in code behind I can do:
public Window2()
{
InitializeComponent();
vm = new PeopleViewModel();
// we are listening on changes of ViewModel, not ComboBox
vm.PropertyChanged += new PropertyChangedEventHandler(vm_PropertyChanged);
this.DataContext = vm;
}
void vm_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == "SelectedPerson")
{
MessageBox.Show(vm.SelectedPerson.Age.ToString());
}
}
// button1_Click should be probably replaced by Command
private void button1_Click(object sender, RoutedEventArgs e)
{
// sample showing that GUI is updated when ViewModel changes
vm.SelectedPerson = vm.PeopleList[2];
}
Hope this helps, I'm quite new to WPF, I'd like to hear any feedback if this is the right way to use MVVM, I think it's quite elegant since you only deal with the ViewModel and Model in code, and the View can be replaced.

Answer 3

I Found that the best way of implementing this is define some external class for all lookups that i use in grid and embedd them in the template as a static resource

Answer 4

We ended up having classes with static properties for each of of our combo box lists:
(you can't make the class itself static otherwise XAML won't be able to open it, but you won't get compile errors)
For example:
public class ZoneList
{
private static readonly IList<Zone> _Items = new List<Zone>();
public static IList<Zone> Items
{
get { return _Items; }
}
}
and then in XAML:
<UserControl.Resources>
<ResourceDictionary>
<ObjectDataProvider x:Key="myZoneList" ObjectType="{x:Type StaticLists:ZoneList}"/>
</ResourceDictionary>
</UserControl.Resources>
<ComboBox ItemsSource="{Binding Path=Items, Source={StaticResource myZoneList}}"></ComboBox>