Reporting Errors

There are several cases when an exception might be thrown because of invalid input data or some user-related error. For these cases, we define a custom Exception class. When thrown, it will be reported differently than the other "unexpected" exceptions caught in the main program. We try to give as much information as possible about the error, so that user knows how to fix the problem.

namespace LiterateCS.Theme
	using System;
	using System.Text;

	public class LiterateException : Exception

The errors always refer to some file we are processing, so we can define it as a mandatory field of the exception.

		public readonly string FileName;

The other fields that we require are the actual error message, the link to the documentation that helps the user to understand what the application expects, and the inner exception which can be null. Inner exception explains the actual problem; the outer exception gives the context what the application was doing when it encountered the error.

		public LiterateException (string message, string file, string helpLink, 
			Exception innerException) : base (message, innerException)
			FileName = file;
			HelpLink = helpLink;

		public LiterateException (string message, string file, string helpLink)
			: this (message, file, helpLink, null) { }

We format the fields of the exception to a readable layout by overriding the ToString method.

		public override string ToString ()
			var res = new StringBuilder ();
			res.AppendFormat ("Error occurred while accessing file: {0}\n\n", 
			res.AppendLine ("Description:");
			res.AppendLine ("------------");
			res.AppendLine (Message);
			if (InnerException != null)
				res.AppendLine ();
				res.AppendLine ("Detailed Description:");
				res.AppendLine ("---------------------");
				res.AppendLine (InnerException.Message);
			res.AppendLine ();
			res.AppendFormat ("For more information see: {0}", HelpLink);
			return res.ToString ();