C# API Tester for Visual Studio Code

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An intelligent Visual Studio Code extension that automatically detects and tests C# Web API endpoints directly from your code editor with AI-powered smart JSON generation.

✨ Key Features

🔍 Automatic API Detection

• Intelligently recognizes C# Web API controllers and methods
• Parses HTTP method attributes ([HttpGet], [HttpPost], etc.)
• Extracts route templates from [Route] attributes
• Analyzes method signatures and parameter sources

🚀 One-Click Testing

• Execute API calls directly from your code editor
• CodeLens integration with inline "Test API" buttons
• Interactive testing panel with Apifox-style UI
• Multiple endpoints can be tested simultaneously

🎯 Smart Parameter Recognition

• Path Parameters: {id} in routes
• Query Parameters: [FromQuery] attributes
• Request Body: [FromBody] attributes with full C# class parsing
• Headers: [FromHeader] attributes
• Form Data: [FromForm] attributes with file upload support

🤖 AI-Powered JSON Generation

• Generates realistic test data based on C# class definitions
• Understands property names, types, and C# XML comments
• Reads C# class attributes for additional context
• Supports OpenAI, Azure OpenAI, and custom AI providers
• Preserves conversation history per API panel with "View AI" feature
• One-click restore to original template

🌍 Environment Management

• Multiple environment support (Development, Staging, Production, etc.)
• Each environment with custom base URL, base path, and headers
• Quick switching via status bar
• Per-environment header configuration
• Workspace-level settings persistence

📝 Advanced Features

• Body Editor: Full-featured JSON editor with syntax highlighting, formatting, and AI generation
• Form Data Support: Multipart form data with file upload and text fields
• Value Editor: Expandable modal editor for long header/query parameter values
• Response Viewer: Formatted JSON response with syntax highlighting and collapsible structure
• Request History: View AI conversation history and restore original JSON templates
• Smart Tab Selection: Automatically opens the most relevant tab (Form/Body/Query/Headers)
• Performance Optimization: Configurable search strategy (fast/balanced/thorough) for class definition lookup
• Parameter Persistence: Automatically saves and restores test parameters per environment (URL, headers, query params, body, form data)
• Cache Management: Clear cached parameters and class definitions to force fresh API detection

📦 Installation

From VS Code Marketplace

1. Open VS Code
2. Press Ctrl+Shift+X (Windows/Linux) or Cmd+Shift+X (Mac)
3. Search for "C# API Tester"
4. Click Install

From VSIX File

1. Download the .vsix file
2. Open VS Code
3. Press Ctrl+Shift+P → "Extensions: Install from VSIX..."
4. Select the downloaded file

🚀 Quick Start

1. Basic Usage

Open a C# controller file:

[ApiController]
[Route("api/[controller]")]
public class UsersController : ControllerBase
{
    [HttpGet("{id}")]
    public async Task<ActionResult<User>> GetUser(int id)
    {
        // Your code here
    }

    [HttpPost]
    public async Task<ActionResult<User>> CreateUser([FromBody] CreateUserDto userDto)
    {
        // Your code here
    }
}

You'll see "🚀 Test API" buttons above each method. Click to test!

2. Environment Setup

First time using? Set up your environment:

1. Click the environment indicator in the status bar
2. Choose "Add New Environment"
3. Configure:
   • Name: "Development"
   • Base URL: "http://localhost:5000"
   • Base Path: "/api" (optional)
   • Headers: {"Authorization": "Bearer token"}

3. AI Configuration (Optional)

Enable AI-powered JSON generation:

1. Open Settings: Ctrl+, → Search "C# API Tester"
2. Configure AI settings:

   {
     "csharpApiTester.ai.enabled": true,
     "csharpApiTester.ai.provider": "openai",
     "csharpApiTester.ai.apiKey": "sk-...",
     "csharpApiTester.ai.model": "gpt-3.5-turbo"
   }
   

📖 Feature Details

Form Data & File Upload

Support for [FromForm] parameters:

[HttpPost("upload")]
public async Task<IActionResult> UploadFile(
    [FromForm] IFormFile file,
    [FromForm] string title,
    [FromForm] string description)
{
    // Handle file upload
}

The extension automatically:

• Creates a Form tab in the test panel
• Detects file fields (IFormFile, Stream, byte[])
• Supports text fields and file inputs
• Sends multipart/form-data requests

AI Smart Generation

When testing endpoints with complex request bodies:

1. Click "🤖 AI Generate" button in the Body tab
2. AI analyzes your C# class definition including:
   • Property names and types
   • XML documentation comments (/// <summary>)
   • Data annotation attributes
   • Nested class structures

   public class CreateUserDto
   {
       /// <summary>
       /// User's full name
       /// </summary>
       [Required]
       [MaxLength(100)]
       public string Name { get; set; }
   
       /// <summary>
       /// Email address
       /// </summary>
       [EmailAddress]
       public string Email { get; set; }
   
       public int Age { get; set; }
   
       public AddressDto Address { get; set; }
   }
   

3. AI generates realistic test data respecting all constraints
4. View the AI conversation and prompt with "💬 View AI" button
5. Restore original JSON template with "↺ Restore" button
6. All conversation history is preserved per API panel

Tab Priority

The test panel intelligently selects the default tab:

• Form Tab → If [FromForm] parameters exist
• Body Tab → If [FromBody] parameters exist
• Query Tab → If [FromQuery] parameters exist
• Headers Tab → Fallback

Parameter Persistence

The extension automatically saves your test parameters for each API endpoint per environment:

• Auto-save: Parameters are saved when you modify URL, headers, query params, body, or form data
• Auto-restore: Previously saved parameters are restored when you reopen the test panel
• Environment-aware: Each environment maintains separate parameter sets for the same endpoint
• Cached Data: Includes URL, HTTP method, headers, query parameters, request body, and form data

To start fresh with default values, use the "Clear Cache And Test" command from CodeLens or command palette.

⚙️ Configuration

Extension Settings

Setting	Description	Default
csharpApiTester.timeout	Request timeout (ms)	30000
csharpApiTester.enableApiDetection	Enable automatic API detection and CodeLens	true
csharpApiTester.searchStrategy	Class definition search strategy	"balanced"
csharpApiTester.searchFileLimit	Max files to search (custom strategy only)	2000
csharpApiTester.ai.enabled	Enable AI features	false
csharpApiTester.ai.provider	AI provider (openai/azure-openai/custom)	"openai"
csharpApiTester.ai.apiKey	AI API key	""
csharpApiTester.ai.endpoint	AI API endpoint URL	OpenAI default
csharpApiTester.ai.model	AI model name	"gpt-3.5-turbo"
csharpApiTester.ai.maxTokens	Max tokens per request	1000
csharpApiTester.ai.timeout	AI request timeout (ms)	60000
csharpApiTester.ai.systemPrompt	System prompt for AI	Default prompt

Search Strategy

Choose a search strategy based on your project size:

• fast: Searches up to 500 .cs files (best for small projects)
• balanced: Searches up to 1000 .cs files (recommended for most projects)
• thorough: Searches up to 2000 .cs files (for large monorepos)
• custom: Use searchFileLimit setting to specify exact limit

AI Providers

OpenAI

{
  "csharpApiTester.ai.provider": "openai",
  "csharpApiTester.ai.apiKey": "sk-...",
  "csharpApiTester.ai.endpoint": "https://api.openai.com/v1/chat/completions",
  "csharpApiTester.ai.model": "gpt-3.5-turbo"
}

Azure OpenAI

{
  "csharpApiTester.ai.provider": "azure-openai",
  "csharpApiTester.ai.apiKey": "your-azure-key",
  "csharpApiTester.ai.endpoint": "https://your-resource.openai.azure.com/openai/deployments/your-deployment/chat/completions?api-version=2024-02-15-preview",
  "csharpApiTester.ai.model": "gpt-35-turbo"
}

Custom Provider

{
  "csharpApiTester.ai.provider": "custom",
  "csharpApiTester.ai.apiKey": "your-key",
  "csharpApiTester.ai.endpoint": "https://your-api.com/v1/chat/completions"
}

🎯 Advanced Usage

Multiple Environments

Switch between environments quickly:

// .vscode/settings.json
{
  "csharpApiTester.environments": [
    {
      "name": "Development",
      "baseUrl": "http://localhost:5000",
      "basePath": "/api",
      "headers": {
        "Authorization": "Bearer dev-token"
      }
    },
    {
      "name": "Staging",
      "baseUrl": "https://staging-api.example.com",
      "basePath": "",
      "headers": {
        "Authorization": "Bearer staging-token"
      }
    }
  ]
}

Expandable Value Editor

For long header values or query parameters:

• Click the ⤢ icon next to the input field
• Edit in a large textarea
• Save changes back to the field

🔧 Commands

Command	Description
C#HttpRequest: Test API Endpoint	Open test panel for selected endpoint
C#HttpRequest: Clear Cache And Test	Clear cached parameters and class definitions, then test endpoint with fresh data
C#HttpRequest: Manage API Environments	Open environment management dialog
C#HttpRequest: Switch Environment	Quick switch between environments
C#HttpRequest: Configure API Base URL	Set base URL for current environment
C#HttpRequest: Toggle API Detection	Enable/disable automatic API detection
C#HttpRequest: Test Debug	Verify extension activation
C#HttpRequest: Debug API Detection	View detected endpoints in console

📝 Use Cases

This extension is perfect for:

• Backend Developers: Test APIs directly from controller code
• API Development: Rapid prototyping and testing during development
• Documentation: Generate sample requests for API documentation
• Testing: Quick manual testing without leaving your editor
• Learning: Understand API behavior through interactive testing

💡 Tips & Tricks

CodeLens Visibility

• CodeLens buttons appear automatically above API methods
• Use C#HttpRequest: Toggle API Detection to enable/disable
• Refresh the document if CodeLens doesn't appear immediately

AI Generation Best Practices

• Add XML documentation comments for better AI understanding
• Use descriptive property names (e.g., userEmail instead of e1)
• Include data annotation attributes for realistic data generation
• Review and edit AI-generated values before sending requests

Performance Optimization

• For large projects, use "fast" search strategy to improve performance
• For better accuracy with complex DTOs, use "thorough" strategy
• Custom strategy allows fine-tuning based on your specific needs

Parameter Management

• The extension automatically saves your test parameters (headers, body, query params, etc.)
• Parameters are saved separately for each environment
• To reset to default values, use "Clear Cache And Test" command from CodeLens button or command palette
• Cache clearing also refreshes class definitions for accurate request generation

🛠️ Troubleshooting

CodeLens Not Showing

1. Ensure the file is a C# controller with [ApiController] or [Route] attributes
2. Check that API detection is enabled in settings
3. Try reloading the VS Code window (Developer: Reload Window)

AI Generation Failing

1. Verify AI is enabled: csharpApiTester.ai.enabled
2. Check API key is correctly configured
3. Test configuration with a simple endpoint first
4. Check console output for detailed error messages

Environment Not Switching

1. Click the environment indicator in status bar
2. Select desired environment from the list
3. Verify environment settings in workspace settings

🤝 Contributing

Contributions are welcome! Please follow these steps:

1. Fork the repository
2. Create a feature branch: git checkout -b feature/amazing-feature
3. Commit your changes: git commit -m 'Add amazing feature'
4. Push to the branch: git push origin feature/amazing-feature
5. Open a Pull Request

🐛 Bug Reports

Found a bug? Please open an issue with:

• VS Code version
• Extension version
• Steps to reproduce
• Expected vs actual behavior

📄 License

MIT License - see LICENSE file for details.

🙏 Acknowledgments

• Built with VS Code Extension API
• HTTP client powered by Axios
• UI inspired by Apifox
• AI integration with OpenAI and compatible providers

🔗 Links

• GitHub Repository
• VS Code Marketplace
• Report Issues
• Feature Requests

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Enjoy testing your C# APIs! 🚀

If you find this extension helpful, please consider:

• ⭐ Starring the GitHub repository
• 📝 Leaving a review on the VS Code Marketplace
• 🐛 Reporting issues or suggesting features