MatChipSet: set_SelectedChips cannot be used to preselect chips

[peterthomastlc]

When using MatChipSet.SelectedChips to preselect displayed chips in OnAfterRender, the comparison is done on a Hash of the MatChip, so a match will never be found.
As a result, chips cannot be preselected. Suggested fix below...

Reproduction Steps

1. Use the code in the sample/demo application on the 'Chip' page.

2. In the 'Filter ChipSet' section, replace the line
   MatChip[] selectedChips = null;
   with
   MatChip[] selectedChips = new MatChip[] { new MatChip() { Label = "Wedges" } };

3. In the Razor file, add a ref value to the MatChipSet:-

    <MatChipSet @ref="filterChipset" Filter="true" @bind-SelectedChips="selectedChips">
   

4. Override the OnAfterRender method to set the selected chips:-

       protected override void OnAfterRender(bool firstRender)
        {
            if (firstRender)
                filterChipset.SelectedChips = selectedChips;
        }
   

Expected Result
The 'Wedges' chip should be selected when the page is shown.

Actual Result
All chips are deselected.

Suggested Fix
In MatChipSet.cs, at line 75, match on the Label value, not a hash of the MatChip object:-
Replace

var selected = new HashSet<MatChip>(value);
foreach (var chip in _chips)
    chip.IsSelected = selected.Contains(chip);

With

var selected = new HashSet<string>(value.Select(x => x.Label));
foreach (var chip in _chips)
    chip.IsSelected = selected.Contains(chip.Label);

I'd have submitted a pull request, but I'm not a registered contributor...

[SpaceOgre]

It is possible to solve this with using @ref on the MatChip and storing it in an array or something like it. Example:

Markup

<MatChipSet Filter="true" @bind-SelectedChips="selectedChips">
  <MatChip Label="Wedges" IsCheckable="true" @ref="allChips[0]"/>
  <MatChip Label="Circles" IsCheckable="true" @ref="allChips[1]"/>
  <MatChip Label="Squares" IsCheckable="true" @ref="allChips[2]"/>
</MatChipSet>

Code

private MatChip[] allChips = new MatChip[3];
private MatChip[] selectedChips;

protected override void OnAfterRender(bool firstRender)
{
    if (firstRender)
        selectedChips = allChips.Where(x => x.Label == "Wedges").ToArray();
}

It would still be nice with an easier way to do this, but maybe a parameter to access _chips from MatChipSet is enough.