Enable in-place edit for cell in GridControl - wpf

Question

I would like to enable in-place editing for cells in my GridControl. I have set property AllowEditing on TableView and Columns, but data in my cells still cannot be edited after doubleclick on cell. Only "copy" is enabled in context menu. I failed to find a solution.
NavigationStyle property in TableView is set to "Cell"
My xaml.
<dx:PLinqInstantFeedbackDataSource x:Name="PLinqInstantFeedbackDataSource" ListSource="{Binding Path=TestCollectionSource}" DefaultSorting="Property1 ASC"/>
<dxg:GridControl EnableSmartColumnsGeneration="True" ItemsSource="{Binding Path=Data, ElementName=PLinqInstantFeedbackDataSource}" SelectionMode="Cell" IsManipulationEnabled="True">
<dxg:GridControl.View>
<dxg:TableView AllowEditing="True" NavigationStyle="Cell" AllowFilterEditor="True" AlternateRowBackground="CornflowerBlue" ShowAutoFilterRow="True" />
</dxg:GridControl.View>
<dxg:GridControl.Columns>
<dxg:GridColumn FieldName="Property1" AllowEditing="True" ReadOnly="False" />
<dxg:GridColumn FieldName="Number" AllowEditing="True" ReadOnly="False" />
</dxg:GridControl.Columns>
</dxg:GridControl>
EDIT
ViewModel and ListSource class
public class MainWindowViewModel : ObservableObject
{
public MainWindowViewModel()
{
}
private BindingList<TestClass> testCollection;
public BindingList<TestClass> TestCollection
{
get
{
var result = this.testCollection;
if (null == result)
{
lock(this)
{
result = this.testCollection;
if (null == result)
{
result = new BindingList<TestClass>();
for (int i = 0; i < 1000000; i++)
{
result.Add(new TestClass() { Property1 = "test" + i, Number = i % 20 });
}
this.testCollection = result;
}
}
}
return result;
}
}
public IListSource TestCollectionSource
{
get { return new ListSource( ()=> this.TestCollection); }
}
}
public class ListSource : IListSource
{
public readonly Func<IList> innerListProvider;
public ListSource(Func<IList> innerListProvider)
{
this.innerListProvider = innerListProvider;
}
public IList GetList()
{
return this.innerListProvider();
}
public bool ContainsListCollection
{
get { return false; }
}
}
public class TestClass : ObservableObject
{
private string property1;
public string Property1
{
get { return this.property1; }
set
{
this.property1 = value;
RaisePropertyChanged(() => this.Property1);
}
}
private int number;
public int Number
{
get { return this.number; }
set
{
this.number = value;
RaisePropertyChanged(() => this.Number);
}
}
}

Answer 1

I have got an answer from DevExpress support.
PLinqInstantFeedbackDataSource is a read-only data source. If you wish to edit data directly in the grid, bind your source collection to the GridControl.ItemsSource property without using an Instant Feedback data provider.