Archive for November, 2003

One computer – Multiple Versions of IE

Thanks to Lockergnome, the Nov. 18th edition of their IT Professionals newsletter pointed out these two links:

The latter article explains how and why the technique works, and the former link has all the files you need zipped up and ready to install.

I have tried this out, and it seems to work. The different browsers are definitely behaving differently for me. I tried IE v4.01 and some complex client-side scripts did not work as I expected. I also experienced some wierdness with the Address bar, but all is OK now. This could not come at a better time as the test lab in the next aisle is going away as we are moving to a new location. Kudos again to Lockergnome, I consistently get some gems from their newsletters.

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Multiple Select Results in ASP.Net

In our new ASP.Net app, we are using one list box that allows multiple-select. Recently, choosing one of the items in the list produced no results. But items would not be in the list if there were no results, so there must be a problem in the SQL statement related to the multiple-select list or the data.  In classic ASP, you would access the multiple items like this:

    Request.Form(i)(j)

where i is the form item and j is the result of the multiple-select. Unfortunately, that does not work in ASP.Net. If you access the form item directly in ASP.Net, like this:

    Request.Form(i)

it provides a comma-delimited list of the multiple form items. It’s pretty easy to then split the list on the commas, and that was what we were doing. Ahh, the bad item in the list had a comma embedded in its text. So it was splitting inappropriately and creating a bad SQL statement for fetching results. This was the source of the problem here. There must be a way to access the items individually, but it was not obvious to me. I must have stared at the MSDN docs forever trying to find the answer. I had to try three or four different keyword searches on Google before I found an excellent explanation here.

The results of a mulitple-select list are also a NameValueCollection, just like the Request.Form. Once I found that, it was easy to get at the individual items. The entire collection is accessed like this:

    Request.Form.GetValues(i)

and the individual items are accessed like this:

    Request.Form.GetValues(i)(j)

I was really surprised at how difficult it was to find this information. Both of my favorite ASP.Net books, Essential ASP.Net by Fritz Onion and Programming ASP.Net by Dino Esposito both had no mention of the embedded NameValueCollection. This seems like it would be a common problem for developers using forms, but I did not find the answer to be as obvious.

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Temporary Tables in Oracle8i

Our application uses some fairly complex PL/SQL procedures to build reports in temporary tables so that we can access the data as a ref cursor and bind to a grid. We built the tables using “on commit delete rows” when creating the Oracle table. See DBASupport.com for a quick explanation of Oracle’s temporary tables. But calling commit inside the PL/SQL package did not delete the rows as implied by the Oracle documentation. The new data on subsequent calls simply added to what already existed in the table. We are using an Oracle Provider version of the Data Access Application Block, and called the stored procedure like this:

DataResults = Daab.ExecuteDataTable(CommandType.StoredProcedure, ProcName, ProcParametersArray)

To solve the problem, we wrapped the call to the stored procedure in a transaction, even though the procedure only issued select sql statements.

Dim FakeTransaction As OracleTransaction

FakeTransaction = Conn.BeginTransaction(IsolationLevel.Serializable)
DataResults = Daab.ExecuteDataTable(FakeTransaction, CommandType.StoredProcedure, ProcName, ProcParameters)
FakeTransaction.Rollback()

Oddly enough, calling .Commit() did not work as implied by the “on commit delete rows“ command added when creating the table. The data persisted in the table. Calling .Rollback() worked though, as I would expect for any transaction. I was unable to find documentation to tell if there is any perfomance drawback to using IsolationLevel.Serializable versus IsolationLevel.ReadCommitted or IsolationLevel.Unspecified as all three give the desired effect on the temporary table.

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