WopiHost

| Package | Version | Downloads | | ------------- | :-------------: | :-------------: | | WopiHost.Abstractions | | | | WopiHost.Core | | | | WopiHost.Discovery | | | | WopiHost.FileSystemProvider | | | | WopiHost.MemoryLockProvider | | | | WopiHost.Url | | |

Introduction

This project is a sample implementation of a WOPI host. Basically, it allows developers to integrate custom datasources with Office Online Server (formerly Office Web Apps) or any other WOPI client by implementing a bunch of interfaces.

Architecture

The WopiHost project is built using a modular architecture that separates concerns and allows for flexible implementations. Here's how the modules work together:

graph TB
    subgraph "Sample Applications"
        SampleApps["**Sample Applications**<br/>🌐 **WopiHost.Web**<br/>🧪 **WopiHost.Validator**<br/>📝 **WopiHost Sample**"]
    end
    
    subgraph "WOPI Client"
        OOS["**Office Online Server**<br/>Microsoft 365 for the Web"]
    end
    
    subgraph "WopiHost Backend API"
        WopiHost["**WopiHost**<br/>Host Application"]
        Core["**WopiHost.Core**<br/>Controllers & Implementation"]
        
        subgraph "Core Libraries"
            Abstractions["**WopiHost.Abstractions**<br/>Core Interfaces"]
            Discovery["**WopiHost.Discovery**<br/>Client Capabilities"]
            Url["**WopiHost.Url**<br/>URL Generation"]
        end
        
        subgraph "Providers"
            FileSystem["**WopiHost.FileSystemProvider**<br/>File System Storage"]
            MemoryLock["**WopiHost.MemoryLockProvider**<br/>In-Memory Locking"]
            CustomStorage["**Custom Storage**<br/>Cloud, Database, etc."]
            CustomLock["**Custom Locking**<br/>Distributed Locking"]
        end
    end
    
    %% Sample apps embed WOPI client
    SampleApps --> OOS
    
    %% WOPI client depends on WopiHost backend
    OOS --> WopiHost
    
    %% WopiHost host app uses Core implementation
    WopiHost --> Core
    
    %% Core dependencies
    Core --> Abstractions
    Core --> Discovery
    
    %% Library dependencies
    Discovery --> Abstractions
    Url --> Discovery
    Url --> Abstractions
    
    %% Provider implementations
    FileSystem --> Abstractions
    MemoryLock --> Abstractions
    CustomStorage --> Abstractions
    CustomLock --> Abstractions
    
    %% Core uses providers
    Core --> FileSystem
    Core --> MemoryLock
    Core --> CustomStorage
    Core --> CustomLock
    
    %% Styling
    classDef sampleApp fill:#e1f5fe,stroke:#01579b,stroke-width:2px
    classDef wopiClient fill:#fff3e0,stroke:#e65100,stroke-width:2px
    classDef hostApp fill:#f3e5f5,stroke:#4a148c,stroke-width:2px
    classDef coreModule fill:#e8f5e8,stroke:#1b5e20,stroke-width:2px
    classDef libraryModule fill:#e8f5e8,stroke:#1b5e20,stroke-width:2px
    classDef providerModule fill:#fce4ec,stroke:#880e4f,stroke-width:2px
    
    class SampleApps sampleApp
    class OOS wopiClient
    class WopiHost hostApp
    class Core coreModule
    class Abstractions,Discovery,Url libraryModule
    class FileSystem,MemoryLock,CustomStorage,CustomLock providerModule

How It Works

1. Sample Applications: The /sample folder contains complete applications that embed the WOPI client:

   • WopiHost.Web: A web application with file management UI that embeds Office Online Server
   • WopiHost.Validator: A testing tool for WOPI protocol validation
   • WopiHost Sample: A basic WOPI host implementation

2. WOPI Client Integration: The sample applications embed Office Online Server or Microsoft 365 for the Web as a WOPI client component.

3. WopiHost Backend API: The WOPI client depends on the WopiHost backend API (NuGet packages) to serve files:

   • WopiHost.Core: Implements the WOPI REST API endpoints, handles authentication, authorization, and orchestrates all operations
   • WopiHost.Abstractions: Defines the core interfaces for storage, security, and locking functionality
   • WopiHost.Discovery: Queries the WOPI client to understand its capabilities
   • WopiHost.Url: Generates proper WOPI URLs based on discovered capabilities

4. Storage & Lock Providers: The WOPI client uses these providers to access and manage files:

   • WopiHost.FileSystemProvider: File system storage implementation
   • WopiHost.MemoryLockProvider: In-memory locking implementation
   • Custom Providers: You can implement your own storage and locking providers

5. Your Own Applications: You can create your own applications by embedding the WOPI client and referencing the WopiHost NuGet packages.

This modular design allows you to:

• Use the sample applications as starting points for your own WOPI-enabled applications
• Embed the WOPI client in your own applications
• Reference individual WopiHost packages to customize the backend API
• Implement custom providers for your specific storage or infrastructure needs
• Test easily with the included validator and sample implementations

Key Differentiators

• Modular Architecture: Complete separation of concerns with 6 dedicated NuGet packages (Abstractions, Core, Discovery, Url, FileSystemProvider, MemoryLockProvider) allowing selective integration
• WOPI Discovery Integration: Dynamic capability detection that queries Office Online Server to determine supported file types and actions, with intelligent URL template resolution and caching
• Advanced Cobalt Support: Optional MS-FSSHTTP protocol integration for enhanced performance and compatibility with Office Web Apps 2013+ features
• Flexible Storage Abstraction: Complete decoupling from file system with clean interfaces supporting any storage backend (cloud, database, custom APIs) through IWopiStorageProvider
• .NET Aspire Integration: Modern cloud-native development experience with service orchestration, OpenTelemetry observability, and containerization support
• Comprehensive WOPI Compliance: Full implementation of the current WOPI specification including file operations, container operations (basic), and ecosystem support (basic)
• Enterprise-Ready Security: Built-in WOPI proof validation, origin checking, and extensible authentication/authorization with JWT token support
• Production-Ready Features: Health checks, in-memory caching, and sample applications for testing and validation

Usage

Prerequisites

• .NET 8 SDK, .NET 9 SDK, or .NET 10 SDK
• Recommended: VS Code or Visual Studio 2022

Building the app

The WopiHost app targets net8.0, net9.0, and net10.0.

If you need a version that targets an older version of .NET, check out the releases:

• .NET 6
• .NET 5
• .NET Core 2.1 + .NET Framework 4.6
• .NET Core 3.1 + .NET Standard 2.1

If you get errors saying that Microsoft.CobaltCore.*.nupkg can't be found, then just remove the reference or see the chapter