April 2006
Beginner
1114 pages
98h 16m
English
Content preview from Programming Excel with VBA and .NETBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Respond to Excel Exceptions in .NET
In .NET, you handle exceptions using the Visual Basic .NET Try...Catch...End Try construct. When .NET receives an exception from a COM component, such as Excel, it checks the COM exception code (COM identifies exceptions as HRESULTs that are 32-bit numbers) and tries to map that code to one of the .NET exception classes, such as DivideByZeroException.
If .NET can’t map an HRESULT to a .NET exception class, it reports that exception as a COMException. A COMException includes Source and Message properties that are filled in if they are available, plus it includes the HRESULT as an ErrorCode property.
When working with Excel from .NET, you will find that most errors are reported as COMExceptions
and that the Source and Message properties are sometimes, but not always, helpful. For example, referring to a worksheet that doesn’t exist causes an COMException with Source equal to "Microsoft.Office.Interop.Excel" and a Message property "Invalid index". But setting a cell to an invalid value is reported as a COMException with an empty Source property and a Message property set to "Exception from HRESULT: 0x800A03EC".
The following code illustrates causing, catching, and reporting different types of Excel exceptions in .NET:
Private Sub cmdCauseErrors_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles cmdCauseError.Click Try ' This worksheet (9) doesn't exist. m_xl.ActiveWorkbook.Sheets(9).Range("B2").value = 42 Catch ex As System.Runtime.InteropServices.COMException ...Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.