WritableView Implementation

[zerodev1200]

Issues with WritableView Implementation

1. Environment

• Verification performed in WPF

2. Exception When Editing Empty Row in DataGrid

Issue Description

• Double-clicking on the empty row at the bottom of a bound DataGrid triggers an exception in NotifyCollectionChangedSynchronizedViewList

  public int Add(object? value)
  {
  throw new NotImplementedException();
  }

Additional Observations

• No exception occurs when editing cells with existing values
• Editing functionality was working in versions up to v3.0.4
• Hypothesis: In WPF, editing operations alone don't pass through object? IList.this[int index]

3. Unexpected Behavior with WritableView Filter

Added the following code to ObservableCollections.sandbox.ConsoleApp

Reproduction Code

notify[1] = "99999";
view.AttachFilter(x => x % 2 == 0);
Console.WriteLine("view");
foreach (var item in view)
{
    Console.WriteLine(item);
}
Console.WriteLine("");
Console.WriteLine("l(source)");
foreach (var item in l)
{
    Console.WriteLine(item);
}

Current Output

view
0
99999
4

l(source)
0
99999
2
3
4
5

Expected Output

view
0
4

l(source)
0
1
99999
3
4
5

4. Related Improvements

• I have submitted a pull request addressing the overloads of ToWritableNotifyCollectionChanged. #74

[neuecc]

Thank you, I've released 3.1.1, that fixed these issues.

2: I've implement Add operation for WritableNotifyCollectionChanged

Usage example:

IList<string?> bindable = view.ToWritableNotifyCollectionChanged((string? newView, Person original, ref bool setValue) =>
{
    if (setValue)
    {
        // default setValue == true is Set operation
        original.Name = newView;

        // You can modify setValue to false, it does not set original collection to new value.
        // For mutable reference types, when there is only a single,
        // bound View and to avoid recreating the View, setting false is effective.
        // Otherwise, keeping it true will set the value in the original collection as well,
        // and change notifications will be sent to lower-level Views(the delegate for View generation will also be called anew).
        setValue = false;
        return original;
    }
    else
    {
        // default setValue == false is Add operation
        return new Person { Age = null, Name = newView };
    }
});

3: It is bug! I've fixed!

[zerodev1200]

Thank you! However, I'm currently investigating because there's an exception occurring in WPF and it's not working properly...

[zerodev1200]

I may have seen a glimmer of hope. I'll investigate a bit more and submit a PR...!

[neuecc]

thanks, v3.3.0 includes your PR!