Throw Exception from relevant

1_GetOrderQueryHandler.cs

public class GetOrderQueryHandler
{
    .
    .
    .

    public async Task<OrderDto> Handle(GetOrderQuery request, CancellationToken cancellationToken)
    {    
        var order = await _repository.Get(request.OrderId);
        if (order == null)
        {
            throw new ResourceNotFoundException($"Order with {request.OrderId} is not found");
        }
        .
        .
        .
    }
}

2_Order.cs

public class Order : IAggregateRoot 
{
    public int OrderId { get; private set; }
   
    public List<OrderItem> OrderItems { get; private set;} = new List<OrderItem>();
    .
    .
    .   

     public void ProcessOrder()
     {
        if (!OrderItems.Any())
        {
           throw new DomainException("Cannot process order when no items are added");
        }
        .
        .
        .
     }
}

3_CustomAuthorizationHandler.cs

 public class CustomAuthorizationHandler : AuthorizationHandler<CustomRequirement>
 {
        .
        .
        .        

        protected override async Task HandleRequirementAsync(AuthorizationHandlerContext context,
            CustomRequirement requirement)
        {

            if (!context.User.HasClaim(e => e.Type == "SuperImportantClaim")
            {
                throw new UnauthorizedException("User is not authorized");
            }
            .
            .
            .
         }
         
}