I have a simple process that a user uploads and Excel file and I import that into an Oracle database.  The process works fine except when a column goes from text to numbers or vice versa.  If column 2 starts with characters and then switches to numbers, in the code the value goes to null when I get to the numbers. 

Example:

Col2

ABC

XYZ

123

In the code

dr(1) value is

ABC

XYZ

""

I'm using Excel 2002 and ASP.NET 3.5 with VB code behind.

Excel guesses at your column type based on the first 8 rows, and thereafter if they don't look right it inserts null.

See this article for several possible fixes:

http://www.sqldts.com/254.aspx