尝试使用switch语句捕获消息

Question

i am trying to catch a exception in the try catch block of my code. I have few errors such as wrong password/ file not found which have specific messages and i want to set codes if any of the error is found . I am trying to catch the message using switch.

  catch (Exception ex)
            {
  switch (ex.Message.ToString())
                {
                    case "Can't get attributes of file 'p'":
                        Debug.WriteLine("wrong username/password");
                        MainController.Status = "2";
                        break;
                    case "Can't get attributes of file 'p'.":
                        Debug.WriteLine("File is not Available");
                        MainController.Status = "3";
                        break;

                    default:
                        Debug.WriteLine("General FTP Error");
                        MainController.Status = "4";
                        break;
                }
}

i want to use message.contains method so that if i get any part of the error message in the ex.message then it should call the relevant case but i am not able to figure out how to use ex.message.contains . Can anyone help me ?

Answer 1

I would highly recommend refactoring your code to use custom exception handlers rather than rely on this "magic strings" approach. This approach is not only difficult to maintain, but hard to test and debug, as spelling errors are not going to be caught by the compiler.

For example, you could create the following exception handlers:

// Note: can probably be better handled without using exceptions
public class LoginFailedException : Exception
{
    // ...
}

// Is this just a FileNotFound exception?
public class FileNotAvailableException : Exception
{
    // ...
}

public class FtpException : Exception
{
    // ...
}

You would then be able to catch each exception individually:

try
{
    // ...
}
catch (LoginFailedException)
{
    Debug.WriteLine("wrong username/password");
    MainController.Status = "2";
}
catch (FileNotAvailableException)
{
    Debug.WriteLine("File is not Available");
    MainController.Status = "3";
}
catch (FtpException)
{
    Debug.WriteLine("General FTP Error");
    MainController.Status = "4";
}

This approach is type-safe, and allows you to easily test and debug your methods. It also prevents a typo from causing hours of difficult debugging.

Answer 2

不要这样做，而是对每种不同类型的Exception使用单独的catch块。