Limit the Properties Bound to DataGrid in WPF using MVVM

Question

All, a simple question. I have a MVVM application with a DataGrid which I have bound to a ViewModel using

<DataGrid ItemsSource="{Binding Path=Resources}" ...></DataGrid>

where the Resources is defined via

public ObservableCollection<ResourceViewModel> Resources { get; private set; }

In the ResourceViewModel class however, I not only have properties that I want to appear in the DataGrid , but other properties that I do not want to appear in the DataGrid . The ResourceViewmodel class is

public class ResourceViewModel : WorkspaceViewModel, IDataErrorInfo
{
    readonly Resource resource;
    readonly ResourceDataRepository resourceRepository;
    private bool isSelected;

    public ResourceViewModel(Resource resource, ResourceDataRepository resourceRepository)
    {
        if (resource == null)
            throw new ArgumentNullException("resource");
        if (resourceRepository == null)
            throw new ArgumentNullException("resourceRepository");
        this.resource = resource;
        this.resourceRepository = resourceRepository;
    }

    public string KeyIndex 
    { 
        get { return this.resource.KeyIndex; } 
        set 
        {
            if (value == this.resource.KeyIndex)
                return;
            this.resource.KeyIndex = value;
            base.OnPropertyChanged("KeyIndex");
        }
    }

    public string FileName
    {
        get { return this.resource.FileName; }
        set 
        {
            if (value == this.resource.FileName)
                return;
            this.resource.FileName = value;
            base.OnPropertyChanged("FileName");
        }
    }

    public List<string> ResourceStringList
    {
        get { return this.resource.ResourceStringList; }
        set 
        {
            if (Utilities.Utilities.ScrambledEquals<string>(this.resource.ResourceStringList, value))
                return;
            this.resource.ResourceStringList = value;
            base.OnPropertyChanged("ResourceStringList");
        }
    }

    public bool IsSelected
    {
        get { return isSelected; }
        set
        {
            if (value == isSelected)
                return;
            isSelected = value;
            base.OnPropertyChanged("IsSelected");
        }
    }
}

Where I don't want IsSelected to appear in the DataGrid and I want each item in ResourceStringList to appear in a different column of the Datagrid . My questions are:

1. How do I prevent IsSelected from showing [as a Checkbox ] in the DataGrid ?

2. How do I get the binding to the DataGrid to automatically display items in separate columns?

What have you tried:

1. I have attempted to inherit from the ResourceViewmodel class and bind to this instead, but this is disgusting and I would like another more elegant solution; please :].

2. I have no idea how to proceed with this one. The number of items stored in the List is variable and set at runtime - so this needs to be a List .

As always, thanks very much for your time.

Answer 1

I think the options are to turn off auto generation as Silvermind mentioned (ie setting DataGrid.AutoGenerateColumns to false and then defining the columns) or implement ITypedList. For example you could create a derived ObservableCollection that implements ITypedList and returns properties based on some attribute you put on the properties you want to hide.

public partial class MainWindow : Window
{
    public MainWindow()
    {
        this.DataContext = new TypedListObservableCollection<Foo>();

        InitializeComponent();
    }
}

public class TypedListObservableCollection<T> : ObservableCollection<T>
    , ITypedList
{
    public TypedListObservableCollection()
    {
    }

    PropertyDescriptorCollection ITypedList.GetItemProperties(PropertyDescriptor[] listAccessors)
    {
        return TypeDescriptor.GetProperties(typeof(T), new Attribute[] { BrowsableAttribute.Yes });
    }

    string ITypedList.GetListName(PropertyDescriptor[] listAccessors)
    {
        return typeof(T).Name;
    }
}

public class Foo
{
    public string Name
    {
        get;
        set;
    }

    [Browsable(false)]
    public bool IsSelected
    {
        get;
        set;
    }
}

Answer 2

To me its just easier not auto generate columns. But that's a personal preference, so I think the easiest way to not allow some properties to be exposed is to use the power of interfaces :)

1. Bind to ObservableCollection of IResourceViewModel - make Resources property a list of interface instead of a concrete type
2. make ResourceViewModel implement IResourceViewModel
3. in IResourceViewModel remove the properties that you don't want to be visible to the grid from the interface