Exception handling is an interesting topic for me today because I dont know if I am using the right exceptions for the right error. There are a billion of exceptions, so how can we catch/throw these things to provide a better message to the user, or even better, how to correct these errors depending on what the exceptions are?
So, my journey started with, what is the best way to throw exceptions? I came to this blog article that brought up good points to take into account on exceptions:
Taken from this site : http://blogs.msdn.com/b/kcwalina/archive/2006/07/05/657268.aspx Do's 1) Use System namespace exceptions 2) Do use custom exceptions that can be used to resolve the issue (i.e. a user-specific exception that is caught and handled automatically for the user) 3) Throw specific errors Dont's 1) Do not just catch and throw exceptions
In #3 of the Do’s was the issue I was having recently. I would throw exceptions, but maybe not the ones outlined by Microsoft, or the documentation. After doing some Google searches, I found a couple of exception lists that helped with this issue:
1)System.Exception 2)Exception Base Class 3)Exception Hierarchy
Basically, here are the exceptions I found to be helpful:
| # | Exception Name | What it’s used for? | Namespace |
|---|---|---|---|
| 1 | ApplicationException | This is an error that is non-fatal. Think of it like your generic exception to throw. | System |
| 2 | SmtpException | Couldn’t send some e-mail. | System.Net.Mail |
| 3 | AggregateException | If you have more than one error coming back, aggregate them in this exception. | System |
| 4 | ValidationException | Represents the exception that occurs during validation of a data field when the ValidationAttribute class is used. | System.ComponentModel.DataAnnotations |
| 5 | HttpRequestException | Exceptions for http related stuff. It is a base class used in HttpClient and HttpMessageHandler. | System.Net.Http |
| 6 | ArgumentException | The exception that is thrown when one of the arguments provided to a method is not valid. | System |
| 7 | ArithmeticException | The exception that is thrown for errors in an arithmetic, casting, or conversion operation. Side note, you could use System.InvalidCastException for casting, too. | System |
| 8 | DataException | Represents the exception that is thrown when errors are generated using ADO.NET components. | System.Data |
| 9 | OperationAbortedException | This exception is thrown when an ongoing operation is aborted by the user. | System.Data |
| 10 | FormatException | The exception that is thrown when the format of an argument does not meet the parameter specifications of the invoked method. | System |
| 11 | IndexOutOfRangeException | Index out of range, nuff said. | System |
| 12 | InvalidOperationException | If the object, needs to be initialized with the Start() method or something like that, and you don’t call it, use this one. | System |
| 13 | IOException | Issues with IO. | System.IO |
| 14 | NotImplementedException | Used to be temporary to let you know you didn’t finish functionality. | System |
| 15 | NotSupportedException | So, if you try to read a file that isn’t there anymore, you should give this error. | System |
| 16 | NullReferenceException | Used to throw an attempt to use a null object. | System |
| 17 | SerializationException | Used to throw for errors during serializing and deserializing. | System.Runtime.Serialization |
| 18 | SecurityException | A security error. Maybe log in stuff. | System.Security |
| 19 | XmlSyntaxException | For invalid XML, but why is it in Security namespace? I don’t know, you could just use System.Xml.XmlException, too. | System.Security |
| 20 | CommunicationException | Communication issue on server or client. | System.ServiceModel |
| 21 | TimeoutException | Timeout exception. There is also System.TimeoutException | System.ServiceProcess |
| 22 | TypeInitializationException | The exception that is thrown as a wrapper around the exception thrown by the class initializer. This class cannot be inherited. | System |
| 23 | UnauthorizedAccessException | The exception that is thrown when the operating system denies access because of an I/O error or a specific type of security error. | System |
| 24 | FileNotFoundException | File was not found | System.IO |
| 25 | DirectoryNotFoundException | Directory was not found. | System.IO |
| 26 | ArgumentNullException | For when your argument, that you pass in to a function, is null. | System |
| 27 | ObjectDisposedException | Object you are trying to use was disposed already, so you throw this error. | System |
Remember, this is guidelines, so if all else fails, write your own. If you have a general exception that you feel like is missing from the list, throw it in the comments and tell why to use it.