feat: add custom ItemProvider to FluentCombobox

[MarvinKlein1508]

🙋 Feature Request

The FluentCombobox only allows you to define a pre-existing list of items. This limits the usability of this component a lot. It would be great if this component would also allow a custom item provider like FluentAutocomplete.

If both components would offer this feature it would be much easier to bind to a single object. If you rely on a custom item provider this currently only possible with the FluentAutocomplete which requires some hacky tricks to achieve this behaviour.

[vnbaaij]

Done for V5. See https://fluentui-blazor-v5.azurewebsites.net/List/Combobox

Don't think we will be adding this for v4 anymore

[MarvinKlein1508]

@vnbaaij where is it in V5? The link only has documentation for IEnumerable<TItem> but not for a custom method which gets invoked while typing.

PS: I can live with V5 only :)

[MarvinKlein1508]

What I mean is some kind of way like this example from FluentAutocomplete

@using System.Globalization
@inject DataSource Data

<FluentStack Orientation="Orientation.Vertical" VerticalGap="10">

    @* Immediate Delay *@
    <FluentNumberField @bind-Value="_immediateDelay"
                       TValue="int"
                       Label="Immediate Delay"
                       Placeholder="Delay"
                       Min="0"
                       Max="2000"
                       Step="100" />

    
    <FluentAutocomplete TOption="CultureInfo"
                        ImmediateDelay="_immediateDelay"
                        AutoComplete="off"
                        Label="Select Culture"
                        Width="250px"
                        OnOptionsSearch="OnSearch"
                        Placeholder="Select countries"
                        MaximumOptionsSearch="int.MaxValue"
                        MaximumSelectedOptions="2"
                        Virtualize="true"
                        OptionText="@(item => $"{item.DisplayName} - {item.Name}")"
                        @bind-SelectedOptions="@SelectedCultures" />

</FluentStack>




<p>
    <b>Selected</b>: @(String.Join(" - ", SelectedCultures.Select(i => i.Name)))
</p>

@code
{
    private int _immediateDelay;

    IEnumerable<CultureInfo> SelectedCultures = Array.Empty<CultureInfo>();
    CultureInfo[] Cultures = CultureInfo.GetCultures(CultureTypes.AllCultures);

    private void OnSearch(OptionsSearchEventArgs<CultureInfo> e)
    {
        e.Items = Cultures.Where(culture =>
            culture.Name.Contains(e.Text, StringComparison.OrdinalIgnoreCase) ||
            culture.DisplayName.Contains(e.Text, StringComparison.OrdinalIgnoreCase));
    }
}

Within OnSearch I do a query against the database because I don't want to fetch 3000 items into memory at once.

[vnbaaij]

Sorry, I thought you meant to just have the Items. @dvoituron can we add OnSearch too?