Using filehelpers ExcelStorage - Excel File not opening

Question

I am using filehelpers ExcelStorage somewhat like this:

ExcelStorage provider = new ExcelStorage(typeof(Img));
provider.StartRow = 2;
provider.StartColumn = 1;
provider.FileName = "Customers.xls";
provider.HeaderRows = 6;
provider.InsertRecords(imgs.ToArray()); // imgs was a list before

And when I am done inserting records, I would like to open the Excelfile I created (with my software still running). But it seems that Excel is somehow locked. Ie there is an Excel instance running in process manager. When I kill all Excel instances I can open the file. Do I have to dispose the ExcelStorage in some sort of way?

Answer 1

I've used FileHelpers, but not ExcelStorage. The link here suggests that you should probably be using FileHelpers.ExcelNPOIStorage instead.

Looking at the source code for ExcelStorage, there is no public dispose method. There is a private CloseAndCleanup method which is called at the end of InsertRecords. Therefore I don't think there's anything you are doing wrong.

The usage of ExcelNPOIStorage looks very much the same, there is a call to GC.Collect() within the private cleanup method here, so I'd guess that there was a known issue with the cleanup of the prior version of the component.

Answer 2

Your best bet is to grab a copy of HANDLE.EXE which you can use with an elevated command prompt to see what has a handle to the file in question. This may be your code, anti virus or excel (if open). Excel does keep a full lock on a file when open preventing ordinary notepad access etc.

If the process owning the handle to the file is your own code, then see if the handle exists once you have exited back to the development environment. If that clears the handle, then you are not releasing the lock properly and that can be slightly trickier as it will depend on exactly what you have coded.

The CloseAndCleanup function mentioned by @timbo is only called from a few places, the Sheets property and the ExtractRecords / InsertRecords functions. The only other thing to wonder is whether you are seeing any exceptions when it attempts to perform the CloseAndCleanup or the reference count the Excel application hasn't been properly released by the COM system.

If you can replicate this with a small sample app, I will be more than willing to give it a quick test and see what happens.

Note 1 , if you are running your code from within Visual Studio, it may be a process called <APPNAME>.VSHOST.EXE which is visual studio's development process, or if you've turned off Visual Studio hosting, just your <APP>.EXE. If running within IIS for a web page or web service, you will more than likely have a w3p process.

Note 2 , if you run handle without being elevated, it may or may not find the handle to the file in question. Therefore, it is always recommended to run elevated to ensure results are accurate.

Note 3 , the difference between ExcelStorage and ExcelNPOIStorage is that the former deals with .xls and the latter deals with .xlsx if I remember rightly.