Fluent UI Blazor — Consumer Usage Guide

This skill teaches how to correctly use the Microsoft.FluentUI.AspNetCore.Components (version 4) NuGet package in Blazor applications.

Critical Rules

1. No manual <script> or <link> tags needed

The library auto-loads all CSS and JS via Blazor's static web assets and JS initializers. Never tell users to add <script> or <link> tags for the core library.

2. Providers are mandatory for service-based components

These provider components MUST be added to the root layout (e.g. MainLayout.razor) for their corresponding services to work. Without them, service calls fail silently (no error, no UI).

razor
<FluentToastProvider />
<FluentDialogProvider />
<FluentMessageBarProvider />
<FluentTooltipProvider />
<FluentKeyCodeProvider />

3. Service registration in Program.cs

csharp
builder.Services.AddFluentUIComponents();

// Or with configuration:
builder.Services.AddFluentUIComponents(options =>
{
    options.UseTooltipServiceProvider = true;  // default: true
    options.ServiceLifetime = ServiceLifetime.Scoped; // default
});

ServiceLifetime rules:

• ServiceLifetime.Scoped — for Blazor Server / Interactive (default)
• ServiceLifetime.Singleton — for Blazor WebAssembly standalone
• ServiceLifetime.Transient — throws NotSupportedException

4. Icons require a separate NuGet package

dotnet add package Microsoft.FluentUI.AspNetCore.Components.Icons

Usage with a @using alias:

razor
@using Icons = Microsoft.FluentUI.AspNetCore.Components.Icons

<FluentIcon Value="@(Icons.Regular.Size24.Save)" />
<FluentIcon Value="@(Icons.Filled.Size20.Delete)" Color="@Color.Error" />

Pattern: Icons.[Variant].[Size].[Name]

• Variants: Regular, Filled
• Sizes: Size12, Size16, Size20, Size24, Size28, Size32, Size48

Custom image: Icon.FromImageUrl("/path/to/image.png")

Never use string-based icon names — icons are strongly-typed classes.

5. List component binding model

FluentSelect<TOption>, FluentCombobox<TOption>, FluentListbox<TOption>, and FluentAutocomplete<TOption> do NOT work like <InputSelect>. They use:

• Items — the data source (IEnumerable<TOption>)
• OptionText — Func<TOption, string?> to extract display text
• OptionValue — Func<TOption, string?> to extract the value string
• SelectedOption / SelectedOptionChanged — for single selection binding
• SelectedOptions / SelectedOptionsChanged — for multi-selection binding

razor
<FluentSelect Items="@countries"
              OptionText="@(c => c.Name)"
              OptionValue="@(c => c.Code)"
              @bind-SelectedOption="@selectedCountry"
              Label="Country" />

NOT like this (wrong pattern):

razor
@* WRONG — do not use InputSelect pattern *@
<FluentSelect @bind-Value="@selectedValue">
    <option value="1">One</option>
</FluentSelect>

6. FluentAutocomplete specifics

• Use ValueText (NOT Value — it's obsolete) for the search input text
• OnOptionsSearch is the required callback to filter options
• Default is Multiple="true"

razor
<FluentAutocomplete TOption="Person"
                    OnOptionsSearch="@OnSearch"
                    OptionText="@(p => p.FullName)"
                    @bind-SelectedOptions="@selectedPeople"
                    Label="Search people" />

@code {
    private void OnSearch(OptionsSearchEventArgs<Person> args)
    {
        args.Items = allPeople.Where(p =>
            p.FullName.Contains(args.Text, StringComparison.OrdinalIgnoreCase));
    }
}

7. Dialog service pattern

Do NOT toggle visibility of <FluentDialog> tags. The service pattern is:

1. Create a content component implementing IDialogContentComponent<TData>:

csharp
public partial class EditPersonDialog : IDialogContentComponent<Person>
{
    [Parameter] public Person Content { get; set; } = default!;

    [CascadingParameter] public FluentDialog Dialog { get; set; } = default!;

    private async Task SaveAsync()
    {
        await Dialog.CloseAsync(Content);
    }

    private async Task CancelAsync()
    {
        await Dialog.CancelAsync();
    }
}

1. Show the dialog via IDialogService:

csharp
[Inject] private IDialogService DialogService { get; set; } = default!;

private async Task ShowEditDialog()
{
    var dialog = await DialogService.ShowDialogAsync<EditPersonDialog, Person>(
        person,
        new DialogParameters
        {
            Title = "Edit Person",
            PrimaryAction = "Save",
            SecondaryAction = "Cancel",
            Width = "500px",
            PreventDismissOnOverlayClick = true,
        });

    var result = await dialog.Result;
    if (!result.Cancelled)
    {
        var updatedPerson = result.Data as Person;
    }
}

For convenience dialogs:

csharp
await DialogService.ShowConfirmationAsync("Are you sure?", "Yes", "No");
await DialogService.ShowSuccessAsync("Done!");
await DialogService.ShowErrorAsync("Something went wrong.");

8. Toast notifications

csharp
[Inject] private IToastService ToastService { get; set; } = default!;

ToastService.ShowSuccess("Item saved successfully");
ToastService.ShowError("Failed to save");
ToastService.ShowWarning("Check your input");
ToastService.ShowInfo("New update available");

FluentToastProvider parameters: Position (default TopRight), Timeout (default 7000ms), MaxToastCount (default 4).

9. Design tokens and themes work only after render

Design tokens rely on JS interop. Never set them in OnInitialized — use OnAfterRenderAsync.

razor
<FluentDesignTheme Mode="DesignThemeModes.System"
                   OfficeColor="OfficeColor.Teams"
                   StorageName="mytheme" />

10. FluentEditForm vs EditForm

FluentEditForm is only needed inside FluentWizard steps (per-step validation). For regular forms, use standard EditForm with Fluent form components:

razor
<EditForm Model="@model" OnValidSubmit="HandleSubmit">
    <DataAnnotationsValidator />
    <FluentTextField @bind-Value="@model.Name" Label="Name" Required />
    <FluentSelect Items="@options"
                  OptionText="@(o => o.Label)"
                  @bind-SelectedOption="@model.Category"
                  Label="Category" />
    <FluentValidationSummary />
    <FluentButton Type="ButtonType.Submit" Appearance="Appearance.Accent">Save</FluentButton>
</EditForm>

Use FluentValidationMessage and FluentValidationSummary instead of standard Blazor validation components for Fluent styling.

Reference files

For detailed guidance on specific topics, see:

• Setup and configuration
• Layout and navigation
• Data grid
• Theming