Problem with Silverlight ComboBoxItem binding - silverlight

Question

I just can't make the following situation work:
I have a class, with the following implementation:
public class SelectionItem<T> : ViewModelBase where T : Entity
{
private bool? _isSelected;
public bool? IsSelected
{
get { return _isSelected; }
set
{
_isSelected = value;
RaisePropertyChanged("IsSelected");
}
}
public T Item { get; set; }
}
And I have the following property on my ViewModel:
private IEnumerable<SelectionItem<DB_Aux_Pessoas>> _vendedores;
public IEnumerable<SelectionItem<DB_Aux_Pessoas>> Vendedores
{
get
{
return _vendedores;
}
set
{
_vendedores = value;
RaisePropertyChanged("Vendedores");
}
}
Then, in my View, I have the ComboBox:
<ComboBox Margin="3,0,0,0"
Height="23"
Width="200"
ItemsSource="{Binding Vendedores, Mode=TwoWay}"
Grid.Column="1"
Grid.Row="1"
HorizontalAlignment="Left">
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<CheckBox IsChecked="{Binding IsSelected, Mode=TwoWay}" />
<TextBlock Text="{Binding Item.NomeRazaoSocial}" />
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
But when I change the CheckBox on the ComboBoxItem, it does not reflect on the property.
The code for DB_Aux_Pessoas is below:
[MetadataTypeAttribute(typeof(DB_Aux_Pessoas.DB_Aux_PessoasMetadata))]
public partial class DB_Aux_Pessoas
{
// This class allows you to attach custom attributes to properties
// of the DB_Aux_Pessoas class.
//
// For example, the following marks the Xyz property as a
// required property and specifies the format for valid values:
// [Required]
// [RegularExpression("[A-Z][A-Za-z0-9]*")]
// [StringLength(32)]
// public string Xyz { get; set; }
internal sealed class DB_Aux_PessoasMetadata
{
// Metadata classes are not meant to be instantiated.
private DB_Aux_PessoasMetadata()
{
}
public Nullable<short> Cliente { get; set; }
public string Id_Numero { get; set; }
public string NomeRazaoSocial { get; set; }
public Nullable<short> Supervisor { get; set; }
public Nullable<short> Vendedor { get; set; }
}
}
What I am doing wrong here?
Tks in advance.

Answer 1

I can't check this right now, but I'm fairly sure the dependency property IsChecked will only accept a binding to a bool and NOT a Nullable<bool>. You might have to do the conversion in your viewmodel and decide which should be the appropriate default for a null value.

Answer 2

This works fine for me. Add an extra property to give you some visual feedback like this:
public class SelectionItem<T> : ViewModelBase
{
private bool? _isSelected;
public bool? IsSelected
{
get { return _isSelected; }
set
{
_isSelected = value;
RaisePropertyChanged("IsSelected");
RaisePropertyChanged("Feedback");
}
}
public string Feedback
{
get
{
if (!this.IsSelected.HasValue)
{
return "null";
}
if (this.IsSelected.Value)
{
return "yes";
}
return "no";
}
}
public T Item { get; set; }
}
And in your xaml, add an extra TextBlock to show the result:
<ComboBox Grid.Column="1"
Grid.Row="1"
Height="23"
Margin="3,0,0,0"
Width="200"
HorizontalAlignment="Left"
ItemsSource="{Binding Vendedores, Mode=TwoWay}">
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<CheckBox IsChecked="{Binding IsSelected, Mode=TwoWay}" />
<TextBlock Text="{Binding Item.NomeRazaoSocial}" />
<TextBlock Text="{Binding Feedback}" Margin="5,0,0,0" />
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
If you see "Yes", "No", "Null" changing as you click the checkboxes, then it's working. Your code worked for me.

Answer 3

public static readonly DependencyProperty IsCheckedProperty = DependencyProperty.RegisterAttached("IsChecked", typeof(bool), typeof(...),
new PropertyMetadata(false, delegate(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
...
}
IsChecked is bool. You can possibly track BindingExpression Error in Output window.