如果搜索失败，我应该返回什么结果？

Question

I have a simple RESTFull service which can gets and search some post entities. My project have three common layers (ORM, DAL, BLL). Should I use try/catch expressions in my controllers or I need to do it on lower layers such as DAL or BLL? I want to check executing of my operations in DAL layer and then check for null values in controllers in order to returns bad status code. Is there a more elegant way for this?

This is one of my methods:

[HttpGet]
public IHttpActionResult Details(int id)
{
    BllTask task;

    try
    {
        task = taskService?.GetById(id);
    }
    catch(Exception exc)
    {
        // change type of exception
        // handle it 
        // log it
        return InternalServerError();
    }

    return Json(task);
}

Answer 1

You should never use a try and catch statement in a controller, the controller should be very simple, also known as a thin controller. If the controller includes complex logic, which then requires a try and catch statement to wrap it, you are doing something wrong.

See the following link for why a thin controller is important .

The try and catch expressions should be used in the ORM, DAL and BLL layers, this is because you want to catch exceptions early, if there is enough context to make sense of the exception.

Then, either handle the exception if you can, or rethrow if required, in exceptional circumstances you can ignore the exception, rather than allowing exceptions unwind all the way to the controller, allowing your software to provide a reliable service.

For exceptions you decide not to handle, you should log them, as a comment in the code provided suggests you will, allowing you to review the logs to see if there is a reoccurring problem, and fix issues where required.

See the following on when to catch early or late .

The presentation layer should then, either display a message saying no search results were found, as the response it got was the expected response, or if an exception unwinds all the way to the presentation layer, the presentation layer should display an error message.

Update

As you have now provided a code example, in the case of the code provided, you would be better off removing the try catch statement, it is pointless. Instead, the following would have the same outcome, if the other layers followed the conventions mentioned in the links:

[HttpGet]
public IHttpActionResult Details(int id)
{
    BllTask task = taskService?.GetById(id);
    return Json(task);
}