My scenario is that I am trying to save a new Lead which has property UserId, but because I have too many leads, I added categories to users, so a user can only have one category.
For this, I created two autocompletes, one for the category and one for users.
The autocomplete for category should set CategoryId value when selected, CategoryId should be passed to UserAutcomplete so that I can filter all users that belong to the given category.

1. The problem is that CategoryAutcomplete is returning the category name instead of the Id, and therefore I cannot filter the users with the particular category.
2. Second issue is that the function ToStringFunc is supposed to take Func<T, string>, when I try to pass int then it returns error as no overload exists for Func<int, string>

I have a simple Category and User object:

public class CategoryDto 
{
  public int Id { get; set; }
  public string Name { get; set; }
}

public class UserDto 
{
  public int Id { get; set; }
  public string FullName { get; set; }
  public int CategoryId { get; set; }
}

Category autocomplete

public class CategoryAutocomplete : MudAutocomplete<string>
{
  private List<CategoryDto>? _categoryList;
  [Parameter] public int? CategoryId { get; set; }
  [Inject] private ICategoryService ICategoryService { get; set; } = default!;
  public CategoryAutocomplete()
  {
    SearchFunc = SearchNames;
    ToStringFunc = ConvertIdToName;
    Clearable = true;
    ResetValueOnEmptyText = true;
    ShowProgressIndicator = true;
    MaxItems = 50;
  }

  protected override async Task OnParametersSetAsync()
  {
    await LoadCategoryDataAsync();
  }

  private Task LoadCategoryDataAsync()
  {
    _categoryList = ICategoryService.DataSource
      .Where(x => CategoryId == null || x.Id == CategoryId)
      .ToList();
    return Task.CompletedTask;
  }

  private Task<IEnumerable<string>> SearchNames(string value, CancellationToken cancellation)
  {
    if (_categoryList == null)
      return Task.FromResult<IEnumerable<string>>(new List<string>());

    var query = _categoryList.AsQueryable();

    if (!string.IsNullOrWhiteSpace(value))
    {
      query = query.Where(x => x.Name!.Contains(value, StringComparison.OrdinalIgnoreCase));
    }

    var result = query.Select(x => x.Name).Take(MaxItems).ToList();
    return Task.FromResult(result.AsEnumerable())!;
  }

  private string ConvertIdToName(string value)
  {
    return _categoryList?.FirstOrDefault(x => x.Name!.Contains(value, StringComparison.OrdinalIgnoreCase))?.Name ?? string.Empty;
  }
}

User autocomplete:

public class UserAutocomplete : MudAutocomplete<string>
{
  private List<UserDto>? _userList;
  [Parameter] public string? Id { get; set; }
  [Parameter] public int? CategoryId { get; set; }
  [Parameter] public string? FullName { get; set; }

  [Inject] private IUserService UserService { get; set; } = default!;
  public UserAutocomplete()
  {
    SearchFunc = SearchUsers;
    ToStringFunc = ConvertIdToName;
    Clearable = true;
    ResetValueOnEmptyText = true;
    ShowProgressIndicator = true;
    MaxItems = 50;
  }

  protected override async Task OnParametersSetAsync()
  {
    await LoadUserDataAsync();
  }

  private Task LoadUserDataAsync()
  {
    _userList = UserService.DataSource
      .Where(x => Id == null || x.Id == Id).ToList();
    return Task.CompletedTask;
  }

  private Task<IEnumerable<string>> SearchUsers(string value, CancellationToken cancellation)
  {
    if (_userList == null) 
    {
      return Task.FromResult<IEnumerable<string>>(new List<string>());
    }

    var query = _userList.AsQueryable();

    if (!string.IsNullOrWhiteSpace(value))
    {
      query = query.Where(x => x.FullName
      .Contains(value, StringComparison.OrdinalIgnoreCase));
    }

    if (!string.IsNullOrWhiteSpace(FullName))
    {
      query = query.Where(x => !x.FullName.Equals(FullName, StringComparison.OrdinalIgnoreCase));
    }

    var result = query.Select(x => x.Id).Take(MaxItems).ToList();
    return Task.FromResult(result.AsEnumerable());
  }

  private string ConvertIdToName(string id)
  {
    return _userList?.FirstOrDefault(x => x.Id.Equals(id, StringComparison.OrdinalIgnoreCase))?.FullName ?? string.Empty;
  }
}

And I am trying to use both category and user autocomple in a dialog MudDialog as this:

<MudDialog>
  <DialogContent>
    <MudForm Model="@Model" @ref="@_form" Validation="@(Validator.ValidateValue(Model))">
      <MudGrid Spacing="2">
        <MudItem xs="12" sm="4">
          <CategoryAutocomplete Label="Pick a Category"
                                For="@(() => CategoryId)"
                                @bind-Value="CategoryId">
          </CategoryAutocomplete>
        </MudItem>
        <MudItem xs="12" sm="4">
          <UserAutocomplete Label="Pick a User"
                                 For="@(() => Model.UserId)"
                                 FullName="@Model.FullName"
                                 CategoryId="@CategoryId" <--- I want to pass this category id so that I can filter the users that belong to this category
                                 @bind-Value="Model.UserId">
          </UserAutocomplete>
        </MudItem>
      </MudGrid>
    </MudForm>
  </DialogContent>
  <DialogActions>
    <MudButton OnClick="Cancel">Cancel</MudButton>
    <MudLoadingButton Loading="@_saving" OnClick="Submit">Save</MudLoadingButton>
  </DialogActions>
</MudDialog>

@code {
  [CascadingParameter] private MudDialogInstance MudDialog { get; set; } = default!;
  [EditorRequired][Parameter] public AddEditItemCommand Model { get; set; } = default!;
  [Parameter] public Action? Refresh { get; set; }
  [Parameter] public string? CategoryId { get; set; }
  private MudForm? _form;
}

Any hint or possible solution is greatly apprecaited.