.Net Core System.InvalidOperationException: Unable to resolve service for type ‘X’ while attempting to activate ‘Y’

Cause: This occurs when trying to resolve a service, but the DI container cannot find a registration for the required dependency.

Example:

public class MyService
{
    private readonly IRepository _repository;

    public MyService(IRepository repository)  // IRepository not registered
    {
        _repository = repository;
    }
}

Solution: Ensure that all dependencies are properly registered:

services.AddScoped<IRepository, Repository>();