Is there an equivalent to SCHEMA.INI for reading Excel Workbooks - excel

Question

I am currently working on a project that will import data from multiple different sources in a variety of formats and structures - e.g., CSV, fixed-length, other-delimited (tab, pipe, etc.) plain-text, and Excel worksheets/workbooks. For this, I'm attempting to build "generic" readers for these files which will throw the files' contents into a DataTable/DataSet I can use in other methods. The plain-text files are pretty simple as I've created a large SCHEMA.INI file which contains field definitions for each of the files the system will handle. That SCHEMA.INI resides in a "processing folder" where the files are temporarily stored until their data has been integrated with other systems. A defined text files' data can be easily extracted using this method:
Private Function TextFileToDataTable(ByVal TextFile As IO.FileInfo) As DataTable
Dim TextFileData As New DataTable("TextFileData")
Using TapeFileConnect As New OleDb.OleDbConnection("Provider=Microsoft.Jet.OleDb.4.0;Data Source='" + TextFile.DirectoryName + "';Extended Properties='Text';")
Using TapeAdapter As New OleDb.OleDbDataAdapter(String.Format("SELECT * FROM {0};", TextFile.Name), TapeFileConnect)
Try
TapeAdapter.Fill(TextFileData)
Catch ex As Exception
TextFileData = Nothing
End Try
End Using
End Using
Return TextFileData
End Function
This works well because a plain-text file isn't terribly complex in its data structure. A single file generally (at least for my requirements) contains, at most, one single table's worth of data - unless, of course, it's some sort of complex XML or JSON structure file, which can/should be handled completely differently anyway - so there's no need to go iterating through different elements beyond this.
NOTE: The code above is dependent on the SCHEMA.INI file being present in the same directory as the plain-text file being read and there being a section within that SCHEMA.INI defined with the same name as that plain-text file.
EXAMPLE:
[EXAMPLE_TEXT_FILE.TXT]
CharacterSet=ANSI
Format=FixedLength
ColNameHeader=FALSE
DateTimeFormat="YYYYMMDD"
COL1=CUSTOMER_NUMBER TEXT WIDTH 20
COL2=CUSTOMER_FIRSTNAME TEXT WIDTH 30
COL3=CUSTOMER_LASTNAME TEXT WIDTH 40
COL4=CUSTOMER_ADDR1 TEXT WIDTH 40
COL5=CUSTOMER_ADDR2 TEXT WIDTH 40
COL6=CUSTOMER_ADDR3 TEXT WIDTH 40
...
Excel workbooks, however, can be a bit trickier. Several of the workbooks I have to process contain multiple worksheets worth of data that I want to consolidate into a single DataSet with a DataTable for each worksheet. The basic functionality is, again, fairly straightforward and I've come up with the following method to read any and all sheets into a DataSet:
Private Function ExcelFileToDataSet(ByVal ExcelFile As IO.FileInfo, ByVal HasHeaderRow As Boolean) As DataSet
Dim ExcelFileData As New DataSet("ExcelFileData")
Dim ExcelConnectionString As String = String.Empty
Dim UseHeaders As String = "NO"
Select Case ExcelFile.Extension.ToUpper.Trim
Case ".XLS"
ExcelConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source={0};Extended Properties='Excel 8.0;HDR={1}'"
Case ".XLSX"
ExcelConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties='Excel 8.0;HDR={1}'"
End Select
If HasHeaderRow Then
UseHeaders = "YES"
End If
ExcelConnectionString = String.Format(ExcelConnectionString, ExcelFile.FullName, UseHeaders)
Try
Using ExcelConnection As New OleDb.OleDbConnection(ExcelConnectionString)
Dim ExcelSchema As New DataTable
ExcelConnection.Open()
ExcelSchema = ExcelConnection.GetOleDbSchemaTable(OleDb.OleDbSchemaGuid.Tables, Nothing)
For Each ExcelSheet As DataRow In ExcelSchema.Rows
Dim SheetTable As New DataTable
Using ExcelAdapter As New OleDb.OleDbDataAdapter
Dim SheetName As String = ExcelSheet("TABLE_NAME").ToString
Dim ExcelCommand As New OleDb.OleDbCommand
SheetTable.TableName = SheetName.Substring(0, SheetName.Length - 1)
ExcelCommand.Connection = ExcelConnection
ExcelCommand.CommandText = String.Format("SELECT * FROM [{0}]", SheetName)
ExcelAdapter.SelectCommand = ExcelCommand
ExcelAdapter.Fill(SheetTable)
End Using
ExcelFileData.Tables.Add(SheetTable)
Next ExcelSheet
End Using
Catch ex As Exception
ExcelFileData = Nothing
End Try
Return ExcelFileData
End Function
The above code will work in a majority of the cases I deal with, but my "difficulty" is that there may be some worksheets that have header rows and some that don't within the same workbook. Also, for those worksheets that do not have a header row, I'd like to be able to define the field names and data types similar to how I can with the plain-text SCHEMA.INI. The only thing I have going for me in these cases is that the "client" provides me with a data map to help me identify what data elements are in each field.
What I'd like to know is if there is a way similar to the text file's SCHEMA.INI to define the structure of an Excel workbook and the worksheet(s) it contains - including column data types to avoid the OleDb driver from "misinterpreting" a column's data - ahead of time. I imagine this could be any sort of structured file such as INI, XML, or whatever, but it would need to be capable of identifying whether or not a particular sheet contains a header row or, in lieu of such a row, the (expected) column definitions. Does any such "standard definition" file exist for Excel workbooks?
One thing to note: As you may have noticed in the code for the ExcelFileToDataSet() method, I may be dealing with the older .XLS (97-03) format or the .XLSX (07+) format, so I can't necessarily rely on the workbook being Open XML compliant. I suppose I could try breaking the methods out to one for each extension, but I'd rather find something that I can use regardless of which file format the Excel file is using.