C# Plugins API Reference

Fluent Search supports plugins written in C#. The most common plugin type is a Search App: it receives the user's input and returns results.

This section is written for developers (plugin authors). It focuses on the shape of the APIs and patterns that work well in production plugins.

At a high level:

Implement ISearchApplication to create a Search App
Return ISearchResult items (usually by inheriting SearchResultBase)
Attach actions using ISearchOperation (usually by inheriting SearchOperationBase)
React to the user choosing an operation in HandleSearchResult

This section is an API-oriented companion to the tutorial in Authoring C# plugins.

NuGet packages

Package	Target	Description
Blast.API	`net10.0`	Main package for plugin authors — includes all three assemblies below
Blast.Core	`net10.0`	Foundation types: interfaces, results, objects, search tags
Blast.API.Core	`net10.0`	Platform abstractions: processes, hotkeys, file system, graphics, AI
Blast.API	`net10.0`	High-level helpers: text matching, settings UI, built-in operations

Plugin .csproj requirements:

<TargetFramework>net10.0</TargetFramework>
<EnableDynamicLoading>true</EnableDynamicLoading>
Reference Blast.API with <Private>false</Private> and <ExcludeAssets>runtime</ExcludeAssets>

Package versions align with Fluent Search versions. Pin the exact version you ship against.

Namespaces

Namespace	Contains
`Blast.Core.Interfaces`	`ISearchApplication`, `ISearchResult`, `ISearchOperation`, `IHandleResult`, `IPreviewImageProvider`, `IResultPreviewControlBuilder`, `ISettingsPage`, `ISettingManager`
`Blast.Core.Results`	`SearchResultBase`, `SearchOperationBase`, `HandleResult`, `SearchTag`, `BitmapImageResult`, `CustomSearchResult`, `CustomSearchOperation`, `CopySearchOperation`
`Blast.Core.Objects`	`SearchApplicationInfo`, `SearchRequest`, `ProcessInfo`, `Setting`, `InformationElement`, `SettingPage`
`Blast.API.Search`	`SearchHelper` (text matching/scoring), `SearchWindow`, `SearchMapping`, `SearchResultsCacheManager`, `ActionSearchOperation`, `CopySearchOperation`, `PasteSearchOperation`, `LoadingSearchResult`
`Blast.API.Processes`	`ProcessUtils`, `ProcessManager`, `BackgroundProcessUtils`
`Blast.API.Settings`	`SearchApplicationSettingsPage`, `SettingsUtils`, `GenericTypeControlBuilder`, `AppHotkeySetting`, `ActionSettingButton`
`Blast.API.FileSystem`	`FileUtils`, `DirectoryFinder`
`Blast.API.Graphics`	`BitmapUtils`, `ScreenUtils`
`Blast.API.Hotkeys`	`HotkeyManager`, `HotkeyUtils`
`Blast.API.AI`	`AIUtils` (text similarity)
`Blast.API.Appearance`	`AppearanceUtils`, `TextIcon`
`Blast.API.Controllers`	`KeyboardController`, `MouseController`, `SpeechUtils`

Core architecture

Start here

Topic	Page
The plugin contract	ISearchApplication
The search input model	SearchRequest
Results	SearchResultBase
Operations	SearchOperationBase
Returning actions	HandleResult

Common building blocks

Topic	Page
Search tags	SearchTag
App metadata	SearchApplicationInfo
Settings pages + persistence	Settings
Launching processes / URLs	Processes
Custom preview UI (Avalonia)	Result Preview UI

Utility APIs

Topic	Page
Built-in operations (Copy/Paste/Action)	Built-in Operations
Text matching and scoring	Text Matching
Async enumerable patterns	Async Helpers
Images and bitmaps	Graphics & Images
Result ranking, caching, grouping	Result Behavior Tuning

Complete API surface

Interfaces (Blast.Core.Interfaces)

Interface	Purpose
`ISearchApplication`	The plugin contract — implement this to create a Search App
`ISearchResult`	Full result interface (prefer `SearchResultBase`)
`ISearchOperation`	Action on a result (prefer `SearchOperationBase`)
`ISearchResultHandler`	Base interface for result handling
`IHandleResult`	Return type from handling a result
`IPreviewImageProvider`	Provides icon glyph or bitmap preview
`IResultPreviewControlBuilder`	Creates AvaloniaUI preview controls
`ISettingsPage`	Settings page declaration
`ISettingManager`	Controls default/suggestion behavior
`ISettingMigrationManager`	Migrates old settings values
`IEnablable`	Toggle enable/disable
`IControlEdit`	Create an edit control

Result types (Blast.Core.Results)

Class	Purpose
`SearchResultBase`	Base class for search results
`SearchOperationBase`	Base class for result operations
`HandleResult`	Standard `IHandleResult` implementation
`SearchTag` / `SearchTagDescriptor`	Search tag definitions
`BitmapImageResult`	Image wrapper (Bitmap/Stream → Avalonia)
`InformationalSearchResult`	Result with information elements + image
`CustomSearchResult`	Generic result with dynamic children
`CustomSearchOperation`	Simple operation returning success
`FuncSearchOperation`	Operation backed by `Action` or `Func<Task>`
`CopySearchOperation`	Built-in clipboard copy operation

Data models (Blast.Core.Objects)

Class	Purpose
`SearchApplicationInfo`	Metadata about your Search App
`SearchRequest`	Incoming search parameters
`Setting`	Full-featured setting with change tracking
`ProcessInfo`	Process metadata (PID, title, icon, etc.)
`InformationElement`	Key-value pair for the result UI
`SettingPage`	Settings page model
`SearchType` (enum)	`SearchAll`, `SearchProcess`

Platform abstractions (Blast.API.Core)

Area	Key types
Processes	`IProcessManager`, `IProcessUtils`, `IBackgroundProcess`, `IWindowMonitor`, `ProcessSwitchedEventArgs`
File system	`IFileManagerController`, `IFileUtils`, `IOsDirectoryFinder`, `ApplicationInfo`
Graphics	`IScreenUtils`, `ScreenInfo`
Hotkeys	`Hotkey`, `IHotkeyManager`, `KeyPressedEventArgs`
AI	`IAIUtils`, `IEmbedder`, `ITextSimilarity`
Controllers	Keyboard, Mouse, Speech subdirectories
OS	`IOsNotificationManager`, `IOsOperationProvider`, `IOsSettingsProvider`, `IWindowUtils`

Key design patterns

IAsyncEnumerable for results

SearchAsync returns IAsyncEnumerable<ISearchResult> — yield results as they become available:

public async IAsyncEnumerable<ISearchResult> SearchAsync(SearchRequest request,
    [EnumeratorCancellation] CancellationToken ct)
{
    await foreach (var item in FetchItemsAsync(ct))
    {
        yield return new MySearchResult(item);
    }
}

Cancellation

Always check cancellationToken.IsCancellationRequested and pass the token to async operations. When the user types a new character, the old search is cancelled.

Static operation instances

Pre-allocate operation objects to avoid re-creating them on every search:

public static ISearchOperation CopyOperation { get; } = new CopySearchOperation("Copy");

Settings pages

Use SearchApplicationSettingsPage from Blast.API to auto-generate settings UI from your model class with [Setting] attributes.

Dependencies

Library	Version	Used for
AvaloniaUI	12.x	Custom UI controls and preview panels
SkiaSharp	3.x	Image processing
System.Drawing.Common	10.x	Bitmap handling
YamlDotNet	16.x	YAML serialization (Tasks system)
TextCopy	1.x	Cross-platform clipboard

Versioning

Blast.API package versions align with Fluent Search versions. If you target a specific build, pin the matching version to avoid runtime API mismatches.

Tip: Don't rely on floating pre-release ranges (*-*) in production plugins. Pin the exact version you ship against.