NPOI, XLSX and VB.NET

Question

I'm attempting to use NPOI to convert both XLS and XLSX files to CSV files. Right now my code works perfectly for XLS files but am running into issues with XLSX files.

Here's the code for converting the file(s) to CSV files using NPOI (actually this code converts it to a DataSet, conversion to CSV happens in the next piece of code)

''' <summary>
''' Import file with delimited rows, columns to datatable 
''' </summary>
''' <param name="FilePath">Path to our file</param>
''' <param name="delimiter">string for delimited imported row items</param>
''' <param name="retainHeaders">Including columns header with importing , (if true, the first row will be added as DataColumns) , (if false, DataColumns will be numbers)</param>
''' <param name="worksheetIndex">The index of the worksheet we're wanting to read from</param>
Private Function GenerateDataTableFromXls(ByVal FilePath As String, ByVal delimiter As String, ByVal retainHeaders As Boolean, ByVal worksheetIndex As Integer) As DataSet

    Dim ds As New DataSet
    Dim ext As String = Path.GetExtension(FilePath)
    Try
        'Get the excel from filepath
        Dim workbook As IWorkbook
        Dim worksheet As ISheet
        Dim sheetCount As Integer
        Dim file = New FileStream(FilePath, FileMode.Open)
        If ext.ToLower() = ".xls" Then
            workbook = New HSSFWorkbook(file)
        Else
            workbook = New XSSFWorkbook(file)
        End If


        sheetCount = workbook.NumberOfSheets

        For i As Integer = 1 To sheetCount
            Dim table As New DataTable
            worksheet = workbook.GetSheetAt(i)

            'get Excel rows
            Dim rows As Integer = worksheet.PhysicalNumberOfRows

            'get the column count
            Dim columns As Integer = worksheet.GetRow(0).PhysicalNumberOfCells

            'now for adding the column headers, if retainHeaders is True then we add the
            'actual headers in the XLS file, if not then add the column number as the header
            If retainHeaders Then
                For j As Integer = 0 To columns - 1
                    table.Columns.Add(worksheet.GetRow(0).GetCell(j).ToString())
                Next
            Else
                For k As Integer = 0 To columns - 1
                    table.Columns.Add(k.ToString())
                Next
            End If

            'now we add each row to our new DataTable
            For x As Integer = 0 To rows - 1
                Dim row As DataRow = table.NewRow()
                For y As Integer = 0 To columns - 1
                    row(y) = worksheet.GetRow(x).GetCell(y).ToString()
                Next
                table.Rows.Add(row)
            Next

            ds.Tables.Add(table)
        Next

        worksheet = Nothing
        workbook = Nothing
    Catch ex As Exception
        Me.ReturnMessage = ex.ToString()
    End Try

    Return ds
End Function

Now we convert it to CSV

''' <summary>
''' Method for converting an XLS or XLSX file to CSV format without requiring any 3rd party
''' installs like Excel or the ACE/JET drivers
''' </summary>
''' <param name="delimiter">What's the file being delimited by</param>
''' <param name="retainHeaders">Are we exporting the headers as well</param>
''' <returns></returns>
''' <remarks></remarks>
Public Function WriteToCSV(ByVal delimiter As String, Optional ByVal retainHeaders As Boolean = True) As Boolean
    Try
        'Dim table As DataTable = GenerateDataTableFromXls(ExcelFile.SourceFile, ",", True, ExcelFile.WorksheetNum)
        Dim ds As DataSet = GenerateDataTableFromXls(ExcelFile.SourceFile, ",", True, ExcelFile.WorksheetNum)
        Dim count As Integer = ds.Tables.Count()

        If count > 1 Then
            For i As Integer = 0 To ds.Tables.Count() - 1
                If ds.Tables(i).Rows.Count() > 0 Then
                    Using writer = New StreamWriter(String.Format(ExcelFile.TargetFile & "{0}.txt", (i + 1).ToString()))
                        For Each row As DataRow In ds.Tables(i).Rows
                            Dim first As Boolean = True
                            For Each column As DataColumn In ds.Tables(i).Columns
                                If Not first Then
                                    writer.Write(",")
                                Else
                                    first = False
                                End If
                                Dim data = row(column.ColumnName).ToString().Replace("""", """""")
                                writer.Write(String.Format("""{0}""", data))
                            Next
                            writer.WriteLine()
                        Next

                    End Using
                Else
                    Throw New Exception(Me.ReturnMessage)
                End If
            Next
        Else
            If ds.Tables(0).Rows.Count() > 0 Then
                Using writer = New StreamWriter(ExcelFile.TargetFile & ".txt")
                    For Each row As DataRow In ds.Tables(0).Rows
                        Dim first As Boolean = True
                        For Each column As DataColumn In ds.Tables(0).Columns
                            If Not first Then
                                writer.Write(",")
                            Else
                                first = False
                            End If
                            Dim data = row(column.ColumnName).ToString().Replace("""", """""")
                            writer.Write(String.Format("""{0}""", data))
                        Next
                        writer.WriteLine()
                    Next

                End Using
            Else
                Throw New Exception(Me.ReturnMessage)
            End If
        End If
        Return True
    Catch ex As Exception
        Me.ReturnMessage = ex.ToString()
        Return False
    Finally
        If File.Exists(ExcelFile.SourceFile) Then
            File.Delete(ExcelFile.SourceFile)
        End If
    End Try
End Function

The error I'm getting is:

System.IndexOutOfRangeException: Cannot find table 0. at System.Data.DataTableCollection.get_Item(Int32 index) at CSVConverter.Converter.WriteToCSV(String delimiter, Boolean retainHeaders) in E:\\LodgingLogistics\\Lodgx\\CSVConverter\\Converter.vb:line 56

Which is this line

If ds.Tables(0).Rows.Count() > 0 Then

Can someone take the time to show me where I'm going wrong here. I use NPOI because I am stuck using .NET 2.0 for the time being.

Answer 1

You're getting that error because it is entering that function with no tables found. You're COUNT variable is 0 causing it to execute the ELSE statement, where it assumes you have 1 table.

Make sure you're using the latest version of NPOI.