如果在数据库中找不到记录，是否返回(RecordNotFound)异常或null

我真的不确定在处理数据库中找不到的记录时，首选的方法是什么。写返回null的Find方法更好还是写返回RecordNotFoundException的Get方法更好？

[AuthenticateFilter(UsernameAndSecretKey)]
[Route("api/v1/activities/emails/{id}")]
[HttpGet]
public IHttpActionResult GetEmailActivity(int id)
{
  try
  {
    // business logic service, could use only db service but this way we can do unit tests (just fill bl service method with fake objects)
    var service = new EmailActivityBlService();
    // 1. use Find method which returns null in case record with provided id does not exist in db
    var model = service.FindActivity(id);
    if( model != null )
      return Ok(model);
    return NotFound();  
   // 2. or is this approach better
   // throws RecordNotFoundException in case row by id is not found in database
   return Ok(service.GetActivity(id));
  }
  catch(RecordNotFoundException e) { return NotFound(); }
  catch(Exception e) { return InternalServerError(e); }
}

EmailActivityBlService有下一个代码，以防有人感兴趣(只显示重要部分(：

private EmailActivityDbService _dbService;
public EmailActivityModel GetActivity(int id)
{
  var model = this._dbService.GetActivity(id);
  if( model == null )
    throw new RecordNotFoundException(); // I suppose System.Data.ObjectNotFound is also suitable
  return model;
}
public EmailActivityModel FindActivity(int id)
{
  // typical entity framework query
  // using(var context = new ..) { return contect.EmailActivity.Where()..SingleOrDefault().ConvertToModel();
  return this._dbService.GetActivity(id);
}

更新

与我的同事交谈后，我们决定采用这个解决方案。至于为什么GetActivity返回null而不是抛出Exception，我更喜欢rboe的答案：

因此，如果是，则返回null。这可能发生在您的域中，即记录不存在(根据我的经验，这种情况最常见(。如果您希望记录存在，但它不存在，那么抛出异常是有效的。

[AuthenticateFilter(UsernameAndSecretKey)]
[Route("api/v1/activities/emails/{id}")]
[HttpGet]
public IHttpActionResult GetEmailActivity(int id)
{
   var service = new EmailActivityBlService();
   var model = service.GetActivity(id); // returns null in case activity is not found
   if( model != null )
     return Ok(model);
   return NotFound();
}

我们避免了方法中的任何try-catch，并在出现异常时设置全局筛选器：

文件：App_Start''WebApiConfig.cs

public class WebApiExceptionFilter : ExceptionFilterAttribute
{
  public override void OnException(HttpActionExecutedContext actionExecutedContext)
  {
    actionExecutedContext.Response = actionExecutedContext.Request.CreateErrorResponse(HttpStatusCode.InternalServerError, actionExecutedContext.Exception.Message, actionExecutedContext.Exception);
  }
}