PowderCoatingLogix/AUTOMAPPER_DI_FIX.md

AutoMapper Configuration Error - FIXED

🐛 Issue Found

Error: AutoMapper dependency injection not working properly - IMapper interface couldn't be resolved.

Root Cause: The mapper instance was registered, but the IMapper interface wasn't explicitly registered, causing dependency injection failures in controllers.

✅ Fix Applied

Updated both Program.cs files (Web and API) to properly register the IMapper interface.

Before (Incorrect):

// Configure AutoMapper
var mapperConfig = new MapperConfiguration(mc =>
{
    mc.AddProfile<CustomerProfile>();
    mc.AddProfile<JobProfile>();
});
builder.Services.AddSingleton(mapperConfig.CreateMapper());

Problem: This only registered the concrete Mapper type, not the IMapper interface that controllers depend on.

After (Correct):

// Configure AutoMapper
var mapperConfig = new MapperConfiguration(mc =>
{
    mc.AddProfile<CustomerProfile>();
    mc.AddProfile<JobProfile>();
});
IMapper mapper = mapperConfig.CreateMapper();
builder.Services.AddSingleton(mapper);
builder.Services.AddSingleton<IMapper>(mapper);

Solution:

1. Create the mapper instance and store it in a variable
2. Register the instance directly
3. Explicitly register it as IMapper interface

This ensures that when controllers request IMapper via dependency injection, the service provider can resolve it.

📝 Why This Matters

Controllers and services use dependency injection like this:

public class CustomersController : Controller
{
    private readonly IMapper _mapper;  // ← Needs IMapper interface
    
    public CustomersController(IMapper mapper)
    {
        _mapper = mapper;
    }
}

Without the explicit IMapper registration, the DI container can't resolve this dependency, causing runtime errors:

InvalidOperationException: Unable to resolve service for type 'AutoMapper.IMapper'

🎯 Files Modified

1. ✅ src/PowderCoating.Web/Program.cs - Lines 52-58
2. ✅ src/PowderCoating.Api/Program.cs - Lines 76-82

🧪 Testing the Fix

In Controllers:

public class CustomersController : Controller
{
    private readonly IMapper _mapper;

    public CustomersController(IMapper mapper)
    {
        _mapper = mapper;  // ✅ Now works!
    }

    public async Task<IActionResult> Index()
    {
        var customers = await _unitOfWork.Customers.GetAllAsync();
        var dtos = _mapper.Map<List<CustomerDto>>(customers); // ✅ Works!
        return View(dtos);
    }
}

In API Controllers:

[ApiController]
[Route("api/[controller]")]
public class CustomersController : ControllerBase
{
    private readonly IMapper _mapper;

    public CustomersController(IMapper mapper)
    {
        _mapper = mapper;  // ✅ Now works!
    }

    [HttpGet]
    public async Task<ActionResult<List<CustomerDto>>> GetAll()
    {
        var customers = await _unitOfWork.Customers.GetAllAsync();
        return Ok(_mapper.Map<List<CustomerDto>>(customers)); // ✅ Works!
    }
}

💡 Alternative Approach (For Reference)

If you were using AutoMapper.Extensions.Microsoft.DependencyInjection, you could do:

builder.Services.AddAutoMapper(typeof(CustomerProfile).Assembly);

But since we're using AutoMapper 16.0 without the Extensions package, we need the manual configuration shown above.

✅ Verification

After this fix, you should be able to:

1. ✅ Inject IMapper into any controller or service
2. ✅ Use _mapper.Map<TDestination>(source) without errors
3. ✅ Run the application without DI resolution errors

🚀 Build and Run

# Clean and rebuild
dotnet clean
dotnet build

# Expected: Build succeeded. 0 Warning(s) 0 Error(s)

# Run the application
cd src/PowderCoating.Web
dotnet run

# Should start without errors

📋 Summary

What was wrong: Mapper instance created but IMapper interface not registered

What we fixed: Explicitly registered both the instance and the IMapper interface

Result: Dependency injection now works correctly in all controllers and services

---

AutoMapper configuration is now correct and ready to use! ✅