public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
{
ISellerRepository sellerRepository = (ISellerRepository)context.HttpContext.RequestServices.GetService(typeof(ISellerRepository));
CreateSellerContactDTO sellerContactDTO = (CreateSellerContactDTO)context.ActionArguments["sellerContactDTO"];
if (!await sellerRepository.ExistsAsync(sellerContactDTO.SellerId))
{
context.ModelState.AddModelError("SellerId", "The given seller id does not correspond to an existing seller");
}
await next();
}
