HOw do I handle exceptions

Question

1.00/5 (2 votes)

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My custom exception isn't working, please can anyone give me some advice???

public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Validator_Click(object sender, RoutedEventArgs e)
        {

            catchingException test = new catchingException();

            try 
            {
                
                
               //Validating Order
                
                XmlReaderSettings settings = new XmlReaderSettings();
                settings.Schemas.Add( "OrderValidator.xsd");
                settings.ValidationType = ValidationType.Schema;


                XmlReader order = XmlReader.Create("order.xml", settings);
                XmlDocument xdoc = new XmlDocument();
                xdoc.Load(order);

                ValidationEventHandler handler = new ValidationEventHandler(ValidationEventHandler);

                xdoc.Validate(handler);
               // test.catchException();
                    
            }
         
            catch (databasetypeException val)
            {
               
                MessageBox.Show(val.Message);

            }
        }

C#

[Serializable]
   public class databasetypeException : Exception
   {
       public databasetypeException()
           : base()
       {
       }
       public databasetypeException(string message)
           : base(message)
       {
       }
       public databasetypeException(string message, Exception innerException)
           : base(message, innerException)
       {
       }
       public databasetypeException(SerializationInfo info, StreamingContext context)
           : base(info, context)
       {
       }

       public void catchException()
       {
           Exception format = new Exception("Format is invalid ");
           throw format;
       }
   }
   }

Posted 8-Apr-14 10:26am

Alexander24

Updated 8-Apr-14 10:29am

v3

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Comments

Richard C Bishop 8-Apr-14 16:40pm

What is not working about it?

David_Wimbley 8-Apr-14 16:43pm

The reason why its not working is because whatever code being executed in your try block doesn't throw a databasetypeException error.

What would be helpful is a stack trace of what it is you are seeing as my VPN to your desktop is currently out of service. Also, could include whatever code you've got in there that is suppose to throw the databaseTypeException...my guess is the code is probably throwing an ArgumentException or something "generic" and that is why it isn't hitting the try block.

Alexander24 8-Apr-14 17:07pm

I get an error in the try block: to be specific in xdoc.load(order); what do you mean with doesn't throw a databasetype error

Sergey Alexandrovich Kryukov 8-Apr-14 17:01pm

"Not working..." is not informative.
—SA

Alexander24 8-Apr-14 17:17pm

Thank you for your advice, and you right, I have been spending a lot of my time learning C#. If you have any other advice feel free to tell me :)

Sergey Alexandrovich Kryukov 8-Apr-14 17:22pm

Very good. I got one answer post for you. Are you going to accept it formally (green "Accept" button). In all cases, your follow-up questions will be welcome.
Good luck in your learning.
—SA

Alexander24 8-Apr-14 17:44pm

I just did, I read those articles the first time. I have also watched some videos on YouTube. My problem is that I would like to make sure the UI group gets a customized message for every exception

Sergey Alexandrovich Kryukov 8-Apr-14 17:48pm

You need to centralize the exception handling of all exception types in a single try-catch block of your thread. If you have more then one thread throwing the same application, you would need to use some special technique...
—SA

Alexander24 8-Apr-14 19:40pm

i have created my own exception which includes a custom message,can you advice me on how do I add such exception in my try-catch block please

2 solutions

Solution 2

Here I am still dealing with my problem, my question is. after I have created my custom exception which includes a custom message, how do call or add that exception to my try-catch block. thank you everyone for your help

namespace ValidationProgram
{
    [Serializable]
    public class MyException : Exception
    {
        public MyException() { }
        public MyException(string message) : base(message) { }
        public MyException(string message, Exception inner) : base(message, inner) { }
        protected MyException(
          System.Runtime.Serialization.SerializationInfo info,
          System.Runtime.Serialization.StreamingContext context)
            : base(info, context) { }
    }

}

C#

namespace ValidationProgram
{
    public class testException : MyException
    {
        public override string Message
        {
            get
            {
                return "data type is incorrect";
            }
        }
    }
}

Posted 8-Apr-14 13:37pm

Alexander24

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Sergey Alexandrovich Kryukov · Accepted Answer · 2014-04-08T11:12:00

The code, exception-wise, makes no sense at all, that's why. First of all, you define the exception class databasetypeException, but never throw an instance of it. The method catchException make no sense, it does not catch anything, only throws some exception of unrelated type System.Exception. No wonder: methods catching exceptions make no sense, because you have to use some try-catch blocks anyway. (At the same time, methods handling some exceptions do make sense.) Anyway, you never call this method.

You have only one try-catch block. Most likely, you catch the exception too locally. Usually, exceptions are caught in very few, strategically chosen parts of code; in most cases, you just let them go (propagate) from the current stack frame, far from the stack frame of throwing it. But I cannot blame you for doing it wrong, because I understand you are doing some study, which is good.

I tried to quickly explain this mechanism ("time machine") in my past answers:
Does Exception in C# Constructor Cause Caller Assignment to Fail?[^],
where was stored .net exceptions in operating system[^].

In effect, the idea is to highly isolate "normal" instruction flow from exceptional processing. It helps you to forget about most exceptional cases (including, but not limited to errors) in most of your development cycle.

What else? Traditionally, application-specific exceptions like yours should be derived from System.ApplicationException, not from System.Exception. This is not a big problem, just a matter of neat style of the design of your code, and supportability.

—SA