Set selected items in grid view when using the grid to edit data

[MarkKamberger]

Setup the grid using SetSelected

 <Grid @ref="levelGrid" TItem="Level"
   Class="table table-hover table-bordered marginBottom1"
   Data="_levels"
   AllowFiltering="true"
   AllowSelection="true"
   FixedHeader="true"
   Height="300"
   Unit="Unit.Px"
   SelectionMode="GridSelectionMode.Multiple"
   SelectedItemsChanged="OnSelectedItemsChanged"
   SetSelected="setSelected"
   Responsive="true">

 <GridColumns>
     <GridColumn TItem="Level" HeaderText="Additional Levels" PropertyName="Description">
         @context.Description
     </GridColumn>
 </GridColumns>
 </Grid>

Code:

 HashSet<Level> setSelected = [];

 protected override async Task<Task> OnParametersSetAsync()
 {
      Input = new InputModel
      {
           Description = _course.Description,
           Selectedlevels = _course.AdditionalLevels.Select(x => x.Level).ToHashSet()
      };
      setSelected = _course.AdditionalLevels.Select(x => x.Level).ToHashSet();
     return base.OnParametersSetAsync();
 }
  private Task OnSelectedItemsChanged(HashSet<Level> levels)
  {
       Input.Selectedlevels = levels;
       setSelected = Input.Selectedlevels;
       return Task.CompletedTask;
  }
 private sealed class InputModel
 {
     [Required]
     [Display(Name = "Description")]
     public string Description { get; set; }

     [Required]
     [MinLength(1)]
     public HashSet<Level> Selectedlevels { get; set; }
 }