Read and write CSV (or TSV) in C# and VB.NET

Imports System
Imports GemBox.Spreadsheet

Module Program

    Sub Main()

        ' If using the Professional version, put your serial key below.
        SpreadsheetInfo.SetLicense("FREE-LIMITED-KEY")

        Dim csvOptions As New CsvLoadOptions(CsvType.CommaDelimited) With
        {
            .AllowNewLineInQuotes = True,
            .HasQuotedValues = True,
            .HasFormulas = True
        }

        ' Read CSV file using specified CsvLoadOptions.
        Dim workbook = ExcelFile.Load("%InputFileName%", csvOptions)

        ' Calculate Excel formulas from CSV data.
        Dim worksheet = workbook.Worksheets(0)
        worksheet.Calculate()

        ' Iterate through read CSV records.
        For Each row In worksheet.Rows
            ' Iterate through read CSV fields.
            For Each cell In row.AllocatedCells
                ' Display just the first line of text from Excel cell.
                Dim value = If(cell.Value?.ToString(), String.Empty)
                Console.Write($"{value.Split(vbLf)(0),-25}")
            Next

            Console.WriteLine()
        Next

    End Sub
End Module

Imports GemBox.Spreadsheet

Module Program

    Sub Main()

        ' If using the Professional version, put your serial key below.
        SpreadsheetInfo.SetLicense("FREE-LIMITED-KEY")

        Dim workbook As New ExcelFile()
        Dim worksheet = workbook.Worksheets.Add("Sheet1")

        ' Tabular sample data for exporting into a CSV file.
        Dim skyscrapers = New Object(,) _
        {
            {"Rank", "Building", "City", "Country", "Height (m)", "Height (ft)", "Floors", "Built"},
            {1, "Burj Khalifa", "Dubai", "United Arab Emirates", 829.8, 2722, 163, 2010},
            {2, "Shanghai Tower", "Shanghai", "China", 632, 2073, 128, 2015},
            {3, "Abraj Al-Bait Towers", "Mecca", "Saudi Arabia", 601, 1971, 120, 2012},
            {4, "Ping An Finance Center", "Shenzhen", "China", 599, 1965, 115, 2016},
            {5, "Lotte World Tower", "Seoul", "South Korea", 555.7, 1823, 123, 2016},
            {6, "One World Trade Center", "New York City", "United States", 546.2, 1792, 104, 2014},
            {7, "Guangzhou CTF Finance Centre", "Guangzhou", "China", 530, 1739, 111, 2016},
            {7, "Tianjin CTF Finance Centre", "Tianjin", "China", 530, 1739, 98, 2018},
            {9, "China Zun", "Beijing", "China", 528, 1732, 108, 2018},
            {10, "Willis Tower", "Chicago", "United States", 527, 1729, 108, 1974},
            {11, "Taipei 101", "Taipei", "Taiwan", 508, 1667, 101, 2004},
            {12, "Shanghai World Financial Center", "Shanghai", "China", 494.3, 1622, 101, 2008},
            {13, "International Commerce Centre", "Hong Kong", "China", 484, 1588, 118, 2010},
            {15, "Central Park Tower", "New York City", "United States", 472.4, 1550, 103, 2020},
            {16, "Landmark 81", "Ho Chi Minh City", "Vietnam", 469.5, 1540, 81, 2018},
            {17, "Lakhta Center", "St. Petersburg", "Russia", 462, 1516, 86, 2018},
            {18, "John Hancock Center", "Chicago", "United States", 456.9, 1499, 100, 1969},
            {19, "Changsha IFS Tower T1", "Changsha", "China", 452, 1483, 94, 2017},
            {20, "Petronas Tower 1", "Kuala Lumpur", "Malaysia", 451.9, 1483, 88, 1998},
            {20, "Petronas Tower 2", "Kuala Lumpur", "Malaysia", 451.9, 1483, 88, 1998},
            {22, "Zifeng Tower", "Nanjing", "China", 450, 1476, 89, 2009},
            {22, "Suzhou IFS", "Suzhou", "China", 450, 1476, 98, 2017},
            {24, "The Exchange 106", "Kuala Lumpur", "Malaysia", 445.1, 1460, 95, 2018},
            {25, "Empire State Building", "New York City", "United States", 443.2, 1454, 102, 1931},
            {26, "Kingkey 100", "Shenzhen", "China", 442, 1449, 100, 2011},
            {27, "Guangzhou International Finance Center", "Guangzhou", "China", 438.6, 1445, 103, 2009},
            {28, "Wuhan Center", "Wuhan", "China", 438, 1437, 88, 2017},
            {29, "111 West 57th Street", "New York City", "United States", 435.3, 1428, 82, 2019},
            {30, "Dongguan International Trade Center 1", "Dongguan", "China", 426.9, 1401, 88, 2019},
            {31, "One Vanderbilt", "New York City", "United States", 427, 1401, 58, 2019},
            {32, "432 Park Avenue", "New York City", "United States", 425.5, 1396, 85, 2015},
            {33, "Marina 101", "Dubai", "United Arab Emirates", 425, 1394, 101, 2017},
            {34, "Trump International Hotel and Tower", "Chicago", "United States", 423.2, 1388, 96, 2009},
            {35, "Jin Mao Tower", "Shanghai", "China", 421, 1381, 88, 1998},
            {36, "Princess Tower", "Dubai", "United Arab Emirates", 414, 1358, 101, 2012},
            {37, "Al Hamra Tower", "Kuwait City", "Kuwait", 412.6, 1354, 80, 2010},
            {38, "Two International Finance Centre", "Hong Kong", "China", 412, 1352, 88, 2003},
            {39, "Haeundae LCT The Sharp Landmark Tower", "Busan", "South Korea", 411.6, 1350, 101, 2019},
            {40, "Guangxi China Resources Tower", "Nanning", "China", 402.7, 1321, 85, 2018},
            {41, "Guiyang Financial Center Tower 1", "Guiyang", "China", 401, 1316, 79, 2020}
        }

        ' Write data into Excel cells.
        Dim rowCount As Integer = skyscrapers.GetLength(0)
        Dim columnCount As Integer = skyscrapers.GetLength(1)
        For row As Integer = 0 To rowCount - 1
            For column As Integer = 0 To columnCount - 1
                worksheet.Cells(row, column).Value = skyscrapers(row, column)
            Next
        Next

        ' Format Excel columns.
        worksheet.Columns("E").Style.NumberFormat = "0.0 \m"
        worksheet.Columns("F").Style.NumberFormat = "0,000 \f\t"

        Dim csvOptions As New CsvSaveOptions(CsvType.CommaDelimited) With
        {
            .UseFormattedValues = True
        }

        ' Write CSV file using specified CsvSaveOptions.
        workbook.Save("Skyscrapers.csv", csvOptions)

    End Sub
End Module

Imports System
Imports System.IO
Imports GemBox.Spreadsheet

Module Program

    Sub Main()

        ' If using the Professional version, put your serial key below.
        SpreadsheetInfo.SetLicense("FREE-LIMITED-KEY")

        ' Create large CSV file.
        Using csv = File.CreateText("large-file.csv")
            For i As Integer = 0 To 5_000_000 - 1
                csv.WriteLine(i)
            Next
        End Using

        ' Import all CSV data into multiple sheets.
        Dim workbook = LargeCsvReader.ReadFile("large-file.csv", LoadOptions.CsvDefault)

        ' Display name and rows count of generated sheets.
        For Each worksheet In workbook.Worksheets
            Console.WriteLine($"Name: {worksheet.Name} | Rows: {worksheet.Rows.Count:#,###}")
        Next

    End Sub
End Module

Public NotInheritable Class LargeCsvReader
    Inherits TextReader

    Private Const MaxRow As Integer = 1_048_576
    Private ReadOnly reader As TextReader
    Private ReadOnly options As CsvLoadOptions

    Private currentRow As Integer
    Private finished As Boolean

    Public Shared Function ReadFile(path As String, options As CsvLoadOptions) As ExcelFile
        Dim workbook As New ExcelFile()
        Dim sheetIndex As Integer = 0

        Using reader = New LargeCsvReader(path, options)
            While reader.CanReadNextSheet()
                sheetIndex += 1
                reader.ReadSheet(workbook, $"Sheet{sheetIndex}")
            End While
        End Using

        Return workbook
    End Function

    Private Sub New(path As String, options As CsvLoadOptions)
        Me.reader = File.OpenText(path)
        Me.options = options
    End Sub

    Public Overrides Function ReadLine() As String
        If Me.currentRow = MaxRow Then Return Nothing

        Me.currentRow += 1
        Dim line As String = Me.reader.ReadLine()
        If line Is Nothing Then Me.finished = True

        Return line
    End Function

    Private Sub ReadSheet(ByVal workbook As ExcelFile, ByVal name As String)
        Dim worksheet = ExcelFile.Load(Me, Me.options).Worksheets.ActiveWorksheet
        workbook.Worksheets.AddCopy(name, worksheet)
    End Sub

    Private Function CanReadNextSheet() As Boolean
        If Me.finished Then Return False

        Me.currentRow = 0
        Return True
    End Function

    Protected Overrides Sub Dispose(ByVal disposing As Boolean)
        Me.reader.Dispose()
    End Sub
End Class

Imports System
Imports System.IO
Imports System.Linq
Imports GemBox.Spreadsheet

Module Program

    Sub Main()

        ' If using the Professional version, put your serial key below.
        SpreadsheetInfo.SetLicense("FREE-LIMITED-KEY")

        ' Create large ExcelFile.
        Dim workbook As New ExcelFile()
        Dim worksheet As ExcelWorksheet = Nothing

        Dim max As Integer = 1_048_576
        For index As Integer = 0 To 5_000_000 - 1
            Dim current As Integer = index Mod max
            If current = 0 Then worksheet = workbook.Worksheets.Add($"Sheet{index / max}")
            worksheet.Cells(current, 0).SetValue(index)
        Next

        ' Export multiple sheets into single CSV file.
        Dim options = SaveOptions.CsvDefault
        Using writer = File.CreateText("large-file.csv")
            For Each sheet In workbook.Worksheets
                workbook.Worksheets.ActiveWorksheet = sheet
                workbook.Save(writer, options)
            Next
        End Using

        ' Display number of lines, or records, in generated CSV file.
        Dim csvLinesCount As Integer = File.ReadLines("large-file.csv").Count()
        Console.WriteLine($"Records: {csvLinesCount}")

    End Sub
End Module