Before we can all go out and enjoy our well deserved summer break, we are happy to bring you a new version of the Fluent UI Blazor library. In this version, we've added some awesome new features to existing components, fixed quite some issues, made 1 (small) breaking change and worked hard to just make the library better overall.

The list of changes and additions is too long to describe all of them here. The full list can be found on our GitHub releases page or at the What's New page on our demo and documentation site. In this blog the following changes and (new) features will be highlighted:

  • Breaking change in Option<TType>-class
  • Calendar now offers date range selection
  • List components now inherit from FluentInputBase
  • Autocomplete can sets its height automatically
  • NavMenu now works better in mobile views
  • ProfileMenu adds StartTemplate and EndTemplate
  • TreeView now supports Items and LazyLoadItems parameters
  • Preview packages feed available

Breaking change in Option<TType>-class

The Option<TType>-type is a utility class that can be used to define list of options that are presented in a FluentSelect or any of the other list components. We have examples of showing how this work available on the demo site.

Originally, the Text property in this class was of type TType?. We've changed this in this release so that this property is now of type string?, which, we think, makes much more sense. (The Value property of this type remains as-is (TType?).)

If you are using this type, you'll most probably need to make some (small and simple) changes in your code after upgrading to this version.

Calendar now offers date range selection

Besides offering more ways of selecting dates in the FluentCalendar component, we have now also added date range selection capabilities.

Initially, this feature will only be available for the FluentCalendar with View=Days.

A new bindable property SelectedDates is added to retrieve the selected dates. We also added a SelectDatesHover method that returns a list of dates to be pre-selected on hover. The dates will be selected when the user clicks on this selection. This allows for enabling options such as selecting an entire week or work-week with a single click.

The @bind-SelectedDates:after command can be used to validate the content of selected dates, block or remove them if necessary, or even display an error message.

Code example

<FluentCalendar @bind-SelectedDates="@SelectedRangeCustomized"
                SelectMode="CalendarSelectMode.Range" />

<FluentCalendar @bind-SelectedDates="@SelectedDaysCustomized"
                SelectMode="CalendarSelectMode.Multiple" />

    private ICollection<DateTime> SelectedRangeCustomized = new List<DateTime>();
    private ICollection<DateTime> SelectedDaysCustomized = new List<DateTime>();

    private IEnumerable<DateTime> SelectOneWeek(DateTime date)
        return new[] { date.StartOfWeek(), date.StartOfWeek().AddDays(6) };

    private IEnumerable<DateTime> Select3Days(DateTime date)
        return Enumerable.Range(0, 3).Select(i => date.AddDays(i));

Examples of date range selections

List components now inherit from FluentInputBase

The list components (FluentAutoComplete, FluentCombobox, FluentListbox and FluentSelect) now inherit from FluentInputBase instead of FluentComponentBase.

This allows for the components to partake in form validation and be marked as invalid.

Example of a FluentSelect being marked invalid

Note: Marking a FluentAutocomplete component as invalid does not work yet.

Autocomplete can set its height automatically

We adding a new MaxAutoHeight parameter to the Autocomplete component. By using this, you can make the component use an auto-height with a maximum size. If a value is not set (or is null), the current behavior (a single line with horizontal scroll capabillity) is used.

<FluentAutocomplete MaxAutoHeight="60px" ... />

Example of the new autoheight parameter for Autocomplete

Both the demo site and template created sites now work the same when a NavMenu is shown in a mobile view. Clicking on either a NavGroup's expand/collapse button or the group itself will just expand/collapse that group (when no href set on the group). Clicking a NavLink wich has an href set, will now navigate to that link and subsequently close the menu.

With these change we get consistent behavior in both demo and template sites


NavMenu before adjustments


NavMenu after adjustments

ProfileMenu adds StartTemplate and EndTemplate

We've added StartTemplate and EndTemplate parameters to make it possible to have custom code before/after the avatar inside the button. The CSS variable --fluent-profile-menu-hover can be used to defined the hover background color (overridable).

<FluentProfileMenu Initials="BG" Style="--fluent-profile-menu-hover: var(--neutral-stroke-focus); padding: 4px;">
        Bill Gates

Example of new ProfileMenu parameters

TreeView now supports Items and LazyLoadItems parameters

Over time, we've received a number or requests for a TreeView component which would be able to display a large number of items. This capability is now added to the TreeView:

  1. Add an Items parameter to bind a list of nodes and child nodes. Elements in the list need to implement ITreeViewItem. The included TreeViewItem class already implements this interface.

  2. Add a LazyLoadItems attribute to render HTML only when nodes are expanded.

  3. Add an ItemTemplate to allow complete customization of each element.

  4. Add the bindable SelectedItem property to manage the selected ITreeViewItem.

  5. Add the OnExpandedAsync method to enable dynamic loading of sub-items.


For example, some code to display an "unlimited" tree view.

<FluentTreeView Items="@Items" @bind-SelectedItem="@SelectedItem" LazyLoadItems="true">
        <span style="color: var(--accent-fill-rest); margin: 0 4px;">
            @(context.Items == null ? "" : $"[{context.Items.Count()}]")

Which will be displayed as this:

Example of TreeView with 'unlimited' items

Preview packages feed

By popular demand, we have re-created a preview packages feed. See for details on how to connect your CLI or Visual Studio environments to this feed.

Note: As the preview packages are being created directly from the development branch in the repository, they will not always be stable.

As can be seen from the feed address, our packages are now being created in the .NET Core Engineering (dnceng) environment. A huge step forward for security, stability and longevity of the library!

Much, much more

As said in the beginning of this blog, the items discussed here are only a small part of the large number of changes made in this release. Please visit the What's New page on the demo and documentation site or the GitHub releases page for a complete overview.


A very special thanks goes out to these new contributors:

@msb-incom, @ApacheTech, @StevenTCramer, @MarvinKlein1508, @chris-gander, @adospace and @ksbecker

And also a warm 'thank you' to everyone else that contributed.

Join the discussion

We have a new channel for 'near real-time' communication on the official .NET Discord server. Come join us at #fluentui-blazor @ DotNetEvolution. This means we will no longer be using (or monitoring) the #blazor channel on the FAST Discord server.


The packages will be released on NuGet in the coming days.


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