How do I enumerate through all columns in the usedrange using C#?

Here is a way it can be done in VBA.

For iCt = 1 To Sheet1.UsedRange.Columns.Count
Sheet1.UsedRange.Columns(iCt).ColumnWidth = 5
Next iCt

I don't know enough C# to answer this or your other questions. I
haven't used OfficeDataSourceObject, but glean it's for working with a
database (Access, ODBC, etc.)

Hth,
Merjet