How to Read Excel Files in C# Without Interop: Complete Developer Guide

Imports IronXL
Imports System
Imports System.Linq

' Load Excel workbook from file path
Dim workBook As WorkBook = WorkBook.Load("test.xlsx")

' Access the first worksheet using LINQ
Dim workSheet As WorkSheet = workBook.WorkSheets.First()

' Read integer value from cell A2
Dim cellValue As Integer = workSheet("A2").IntValue
Console.WriteLine($"Cell A2 value: {cellValue}")

' Iterate through a range of cells
For Each cell In workSheet("A2:A10")
    Console.WriteLine("Cell {0} has value '{1}'", cell.AddressString, cell.Text)
Next

' Advanced Operations with LINQ
' Calculate sum using built_in Sum() method
Dim sum As Decimal = workSheet("A2:A10").Sum()

' Find maximum value using LINQ
Dim max As Decimal = workSheet("A2:A10").Max(Function(c) c.DecimalValue)

' Output calculated results
Console.WriteLine($"Sum of A2:A10: {sum}")
Console.WriteLine($"Maximum value: {max}")

Imports IronXL
Imports System
Imports System.Linq

' Load Excel workbook from file path
Dim workBook As WorkBook = WorkBook.Load("test.xlsx")

' Access the first worksheet using LINQ
Dim workSheet As WorkSheet = workBook.WorkSheets.First()

' Read integer value from cell A2
Dim cellValue As Integer = workSheet("A2").IntValue
Console.WriteLine($"Cell A2 value: {cellValue}")

' Iterate through a range of cells
For Each cell In workSheet("A2:A10")
    Console.WriteLine("Cell {0} has value '{1}'", cell.AddressString, cell.Text)
Next

' Advanced Operations with LINQ
' Calculate sum using built_in Sum() method
Dim sum As Decimal = workSheet("A2:A10").Sum()

' Find maximum value using LINQ
Dim max As Decimal = workSheet("A2:A10").Max(Function(c) c.DecimalValue)

' Output calculated results
Console.WriteLine($"Sum of A2:A10: {sum}")
Console.WriteLine($"Maximum value: {max}")

Imports IronXL
Imports System
Imports System.Linq

' Load Excel file from specified path
Dim workBook As WorkBook = WorkBook.Load("Spreadsheets\GDP.xlsx")

Console.WriteLine("Workbook loaded successfully.")

' Access specific worksheet by name
Dim sheet As WorkSheet = workBook.GetWorkSheet("Sheet1")

' Read and display cell value
Dim cellValue As String = sheet("A1").StringValue
Console.WriteLine($"Cell A1 contains: {cellValue}")

' Perform additional operations
' Count non_empty cells in column A
Dim rowCount As Integer = sheet("A:A").Count(Function(cell) Not cell.IsEmpty)
Console.WriteLine($"Column A has {rowCount} non_empty cells")

Imports IronXL
Imports System
Imports System.Linq

' Load Excel file from specified path
Dim workBook As WorkBook = WorkBook.Load("Spreadsheets\GDP.xlsx")

Console.WriteLine("Workbook loaded successfully.")

' Access specific worksheet by name
Dim sheet As WorkSheet = workBook.GetWorkSheet("Sheet1")

' Read and display cell value
Dim cellValue As String = sheet("A1").StringValue
Console.WriteLine($"Cell A1 contains: {cellValue}")

' Perform additional operations
' Count non_empty cells in column A
Dim rowCount As Integer = sheet("A:A").Count(Function(cell) Not cell.IsEmpty)
Console.WriteLine($"Column A has {rowCount} non_empty cells")

Imports IronXL
Imports System

' Get worksheet by name
Dim workSheet As WorkSheet = workBook.GetWorkSheet("GDPByCountry")

Console.WriteLine("Worksheet 'GDPByCountry' not found")
' List available worksheets
For Each sheet In workBook.WorkSheets
    Console.WriteLine($"Available: {sheet.Name}")
Next

Imports IronXL
Imports System

' Get worksheet by name
Dim workSheet As WorkSheet = workBook.GetWorkSheet("GDPByCountry")

Console.WriteLine("Worksheet 'GDPByCountry' not found")
' List available worksheets
For Each sheet In workBook.WorkSheets
    Console.WriteLine($"Available: {sheet.Name}")
Next

Imports IronXL

' Create new XLSX workbook (recommended format)
Private workBook As WorkBook = WorkBook.Create(ExcelFileFormat.XLSX)

' Set workbook metadata
workBook.Metadata.Author = "Your Application"
workBook.Metadata.Comments = "Generated by IronXL"

' Create new XLS workbook for legacy support
Dim legacyWorkBook As WorkBook = WorkBook.Create(ExcelFileFormat.XLS)

' Save the workbook
workBook.SaveAs("NewDocument.xlsx")

Imports IronXL

' Create new XLSX workbook (recommended format)
Private workBook As WorkBook = WorkBook.Create(ExcelFileFormat.XLSX)

' Set workbook metadata
workBook.Metadata.Author = "Your Application"
workBook.Metadata.Comments = "Generated by IronXL"

' Create new XLS workbook for legacy support
Dim legacyWorkBook As WorkBook = WorkBook.Create(ExcelFileFormat.XLS)

' Save the workbook
workBook.SaveAs("NewDocument.xlsx")

Imports IronXL

' Create multiple worksheets with descriptive names
Dim summarySheet As WorkSheet = workBook.CreateWorkSheet("Summary")
Dim dataSheet As WorkSheet = workBook.CreateWorkSheet("RawData")
Dim chartSheet As WorkSheet = workBook.CreateWorkSheet("Charts")

' Set the active worksheet
workBook.SetActiveTab(0) ' Makes "Summary" the active sheet

' Access default worksheet (first sheet)
Dim defaultSheet As WorkSheet = workBook.DefaultWorkSheet

Imports IronXL

' Create multiple worksheets with descriptive names
Dim summarySheet As WorkSheet = workBook.CreateWorkSheet("Summary")
Dim dataSheet As WorkSheet = workBook.CreateWorkSheet("RawData")
Dim chartSheet As WorkSheet = workBook.CreateWorkSheet("Charts")

' Set the active worksheet
workBook.SetActiveTab(0) ' Makes "Summary" the active sheet

' Access default worksheet (first sheet)
Dim defaultSheet As WorkSheet = workBook.DefaultWorkSheet

Imports IronXL
Imports System
Imports System.Linq

' Load workbook and get worksheet
Dim workBook As WorkBook = WorkBook.Load("test.xlsx")
Dim workSheet As WorkSheet = workBook.DefaultWorkSheet

' Access cell B1
Dim cell As IronXL.Cell = workSheet("B1").First()

' Read cell value with type safety
Dim textValue As String = cell.StringValue
Dim intValue As Integer = cell.IntValue
Dim decimalValue As Decimal = cell.DecimalValue
Dim dateValue As DateTime? = cell.DateTimeValue

' Check cell data type
If cell.IsNumeric Then
    Console.WriteLine($"Numeric value: {cell.DecimalValue}")
ElseIf cell.IsText Then
    Console.WriteLine($"Text value: {cell.StringValue}")
End If

Imports IronXL
Imports System
Imports System.Linq

' Load workbook and get worksheet
Dim workBook As WorkBook = WorkBook.Load("test.xlsx")
Dim workSheet As WorkSheet = workBook.DefaultWorkSheet

' Access cell B1
Dim cell As IronXL.Cell = workSheet("B1").First()

' Read cell value with type safety
Dim textValue As String = cell.StringValue
Dim intValue As Integer = cell.IntValue
Dim decimalValue As Decimal = cell.DecimalValue
Dim dateValue As DateTime? = cell.DateTimeValue

' Check cell data type
If cell.IsNumeric Then
    Console.WriteLine($"Numeric value: {cell.DecimalValue}")
ElseIf cell.IsText Then
    Console.WriteLine($"Text value: {cell.StringValue}")
End If

' Write different data types to cells
workSheet("A1").Value = "Product Name" ' String
workSheet("B1").Value = 99.95D ' Decimal
workSheet("C1").Value = DateTime.Today ' Date
workSheet("D1").Formula = "=B1*1.2" ' Formula
											' Format cells
workSheet("B1").FormatString = "$#,##0.00" ' Currency format
workSheet("C1").FormatString = "yyyy-MM-dd" ' Date format
											' Save changes
workBook.Save()

' Write different data types to cells
workSheet("A1").Value = "Product Name" ' String
workSheet("B1").Value = 99.95D ' Decimal
workSheet("C1").Value = DateTime.Today ' Date
workSheet("D1").Formula = "=B1*1.2" ' Formula
											' Format cells
workSheet("B1").FormatString = "$#,##0.00" ' Currency format
workSheet("C1").FormatString = "yyyy-MM-dd" ' Date format
											' Save changes
workBook.Save()

Imports IronXL

' Select range using Excel notation
Dim range As Range = workSheet("D2:D101")

' Alternative: Use Range class for dynamic selection
Dim dynamicRange As Range = workSheet.GetRange("D2:D101") ' Row 2_101, Column D

' Perform bulk operations
range.Value = 0 ' Set all cells to 0

Imports IronXL

' Select range using Excel notation
Dim range As Range = workSheet("D2:D101")

' Alternative: Use Range class for dynamic selection
Dim dynamicRange As Range = workSheet.GetRange("D2:D101") ' Row 2_101, Column D

' Perform bulk operations
range.Value = 0 ' Set all cells to 0

' Data validation example
Public Class ValidationResult
    Public Property Row As Integer
    Public Property PhoneError As String
    Public Property EmailError As String
    Public Property DateError As String
    Public ReadOnly Property IsValid As Boolean
        Get
            Return String.IsNullOrEmpty(PhoneError) AndAlso
                   String.IsNullOrEmpty(EmailError) AndAlso
                   String.IsNullOrEmpty(DateError)
        End Get
    End Property
End Class

' Validate data in rows 2-101
Dim results As New List(Of ValidationResult)()

For row As Integer = 2 To 101
    Dim result As New ValidationResult With {.Row = row}

    ' Get row data efficiently
    Dim phoneCell = workSheet($"B{row}")
    Dim emailCell = workSheet($"D{row}")
    Dim dateCell = workSheet($"E{row}")

    ' Validate phone number
    If Not IsValidPhoneNumber(phoneCell.StringValue) Then
        result.PhoneError = "Invalid phone format"
    End If

    ' Validate email
    If Not IsValidEmail(emailCell.StringValue) Then
        result.EmailError = "Invalid email format"
    End If

    ' Validate date
    If Not dateCell.IsDateTime Then
        result.DateError = "Invalid date format"
    End If

    results.Add(result)
Next

' Helper methods
Private Function IsValidPhoneNumber(phone As String) As Boolean
    Return System.Text.RegularExpressions.Regex.IsMatch(phone, "^\d{3}-\d{3}-\d{4}$")
End Function

Private Function IsValidEmail(email As String) As Boolean
    Return email.Contains("@") AndAlso email.Contains(".")
End Function

' Data validation example
Public Class ValidationResult
    Public Property Row As Integer
    Public Property PhoneError As String
    Public Property EmailError As String
    Public Property DateError As String
    Public ReadOnly Property IsValid As Boolean
        Get
            Return String.IsNullOrEmpty(PhoneError) AndAlso
                   String.IsNullOrEmpty(EmailError) AndAlso
                   String.IsNullOrEmpty(DateError)
        End Get
    End Property
End Class

' Validate data in rows 2-101
Dim results As New List(Of ValidationResult)()

For row As Integer = 2 To 101
    Dim result As New ValidationResult With {.Row = row}

    ' Get row data efficiently
    Dim phoneCell = workSheet($"B{row}")
    Dim emailCell = workSheet($"D{row}")
    Dim dateCell = workSheet($"E{row}")

    ' Validate phone number
    If Not IsValidPhoneNumber(phoneCell.StringValue) Then
        result.PhoneError = "Invalid phone format"
    End If

    ' Validate email
    If Not IsValidEmail(emailCell.StringValue) Then
        result.EmailError = "Invalid email format"
    End If

    ' Validate date
    If Not dateCell.IsDateTime Then
        result.DateError = "Invalid date format"
    End If

    results.Add(result)
Next

' Helper methods
Private Function IsValidPhoneNumber(phone As String) As Boolean
    Return System.Text.RegularExpressions.Regex.IsMatch(phone, "^\d{3}-\d{3}-\d{4}$")
End Function

Private Function IsValidEmail(email As String) As Boolean
    Return email.Contains("@") AndAlso email.Contains(".")
End Function

Imports IronXL

' Add formulas to calculate percentages
Dim lastRow As Integer = 50
For row As Integer = 2 To lastRow - 1
    ' Calculate percentage: current value / total
    workSheet($"C{row}").Formula = $"=B{row}/B{lastRow}"
    ' Format as percentage
    workSheet($"C{row}").FormatString = "0.00%"
Next
' Add summary formulas
workSheet("B52").Formula = "=SUM(B2:B50)"      ' Sum
workSheet("B53").Formula = "=AVERAGE(B2:B50)"  ' Average
workSheet("B54").Formula = "=MAX(B2:B50)"      ' Maximum
workSheet("B55").Formula = "=MIN(B2:B50)"      ' Minimum
' Force formula evaluation
workBook.EvaluateAll()

Imports IronXL

' Add formulas to calculate percentages
Dim lastRow As Integer = 50
For row As Integer = 2 To lastRow - 1
    ' Calculate percentage: current value / total
    workSheet($"C{row}").Formula = $"=B{row}/B{lastRow}"
    ' Format as percentage
    workSheet($"C{row}").FormatString = "0.00%"
Next
' Add summary formulas
workSheet("B52").Formula = "=SUM(B2:B50)"      ' Sum
workSheet("B53").Formula = "=AVERAGE(B2:B50)"  ' Average
workSheet("B54").Formula = "=MAX(B2:B50)"      ' Maximum
workSheet("B55").Formula = "=MIN(B2:B50)"      ' Minimum
' Force formula evaluation
workBook.EvaluateAll()

Imports System.Text.RegularExpressions
Imports IronXL

' Validation implementation
For i As Integer = 2 To 101
    Dim result As New PersonValidationResult With {.Row = i}
    results.Add(result)
    
    ' Get cells for current person
    Dim cells = workSheet($"A{i}:E{i}").ToList()
    
    ' Validate phone (column B)
    Dim phone As String = cells(1).StringValue
    If Not Regex.IsMatch(phone, "^\+?1?\d{10,14}$") Then
        result.PhoneNumberErrorMessage = "Invalid phone format"
    End If
    
    ' Validate email (column D)
    Dim email As String = cells(3).StringValue
    If Not Regex.IsMatch(email, "^[^@\s]+@[^@\s]+\.[^@\s]+$") Then
        result.EmailErrorMessage = "Invalid email address"
    End If
    
    ' Validate date (column E)
    If Not cells(4).IsDateTime Then
        result.DateErrorMessage = "Invalid date format"
    End If
Next i

Imports System.Text.RegularExpressions
Imports IronXL

' Validation implementation
For i As Integer = 2 To 101
    Dim result As New PersonValidationResult With {.Row = i}
    results.Add(result)
    
    ' Get cells for current person
    Dim cells = workSheet($"A{i}:E{i}").ToList()
    
    ' Validate phone (column B)
    Dim phone As String = cells(1).StringValue
    If Not Regex.IsMatch(phone, "^\+?1?\d{10,14}$") Then
        result.PhoneNumberErrorMessage = "Invalid phone format"
    End If
    
    ' Validate email (column D)
    Dim email As String = cells(3).StringValue
    If Not Regex.IsMatch(email, "^[^@\s]+@[^@\s]+\.[^@\s]+$") Then
        result.EmailErrorMessage = "Invalid email address"
    End If
    
    ' Validate date (column E)
    If Not cells(4).IsDateTime Then
        result.DateErrorMessage = "Invalid date format"
    End If
Next i

Imports System

' Create results worksheet
Dim resultsSheet = workBook.CreateWorkSheet("ValidationResults")

' Add headers
resultsSheet("A1").Value = "Row"
resultsSheet("B1").Value = "Valid"
resultsSheet("C1").Value = "Phone Error"
resultsSheet("D1").Value = "Email Error"
resultsSheet("E1").Value = "Date Error"

' Style headers
resultsSheet("A1:E1").Style.Font.Bold = True
resultsSheet("A1:E1").Style.SetBackgroundColor("#4472C4")
resultsSheet("A1:E1").Style.Font.Color = "#FFFFFF"

' Output validation results
For i As Integer = 0 To results.Count - 1
    Dim result = results(i)
    Dim outputRow As Integer = i + 2

    resultsSheet($"A{outputRow}").Value = result.Row
    resultsSheet($"B{outputRow}").Value = If(result.IsValid, "Yes", "No")
    resultsSheet($"C{outputRow}").Value = If(result.PhoneNumberErrorMessage, "")
    resultsSheet($"D{outputRow}").Value = If(result.EmailErrorMessage, "")
    resultsSheet($"E{outputRow}").Value = If(result.DateErrorMessage, "")

    ' Highlight invalid rows
    If Not result.IsValid Then
        resultsSheet($"A{outputRow}:E{outputRow}").Style.SetBackgroundColor("#FFE6E6")
    End If
Next

' Auto-fit columns
For col As Integer = 0 To 4
    resultsSheet.AutoSizeColumn(col)
Next

' Save validated workbook
workBook.SaveAs("Spreadsheets\PeopleValidated.xlsx")

Imports System

' Create results worksheet
Dim resultsSheet = workBook.CreateWorkSheet("ValidationResults")

' Add headers
resultsSheet("A1").Value = "Row"
resultsSheet("B1").Value = "Valid"
resultsSheet("C1").Value = "Phone Error"
resultsSheet("D1").Value = "Email Error"
resultsSheet("E1").Value = "Date Error"

' Style headers
resultsSheet("A1:E1").Style.Font.Bold = True
resultsSheet("A1:E1").Style.SetBackgroundColor("#4472C4")
resultsSheet("A1:E1").Style.Font.Color = "#FFFFFF"

' Output validation results
For i As Integer = 0 To results.Count - 1
    Dim result = results(i)
    Dim outputRow As Integer = i + 2

    resultsSheet($"A{outputRow}").Value = result.Row
    resultsSheet($"B{outputRow}").Value = If(result.IsValid, "Yes", "No")
    resultsSheet($"C{outputRow}").Value = If(result.PhoneNumberErrorMessage, "")
    resultsSheet($"D{outputRow}").Value = If(result.EmailErrorMessage, "")
    resultsSheet($"E{outputRow}").Value = If(result.DateErrorMessage, "")

    ' Highlight invalid rows
    If Not result.IsValid Then
        resultsSheet($"A{outputRow}:E{outputRow}").Style.SetBackgroundColor("#FFE6E6")
    End If
Next

' Auto-fit columns
For col As Integer = 0 To 4
    resultsSheet.AutoSizeColumn(col)
Next

' Save validated workbook
workBook.SaveAs("Spreadsheets\PeopleValidated.xlsx")

Imports System
Imports System.ComponentModel.DataAnnotations
Imports Microsoft.EntityFrameworkCore
Imports IronXL

' Define entity model
Public Class Country
    <Key>
    Public Property Id As Guid = Guid.NewGuid()

    <Required>
    <MaxLength(100)>
    Public Property Name As String

    <Range(0, Double.MaxValue)>
    Public Property GDP As Decimal

    Public Property ImportedDate As DateTime = DateTime.UtcNow
End Class

Imports System
Imports System.ComponentModel.DataAnnotations
Imports Microsoft.EntityFrameworkCore
Imports IronXL

' Define entity model
Public Class Country
    <Key>
    Public Property Id As Guid = Guid.NewGuid()

    <Required>
    <MaxLength(100)>
    Public Property Name As String

    <Range(0, Double.MaxValue)>
    Public Property GDP As Decimal

    Public Property ImportedDate As DateTime = DateTime.UtcNow
End Class

Public Class CountryContext
    Inherits DbContext

    Public Property Countries As DbSet(Of Country)

    Protected Overrides Sub OnConfiguring(optionsBuilder As DbContextOptionsBuilder)
        ' Configure SQLite connection
        optionsBuilder.UseSqlite("Data Source=CountryGDP.db")

        ' Enable sensitive data logging in development
#If DEBUG Then
        optionsBuilder.EnableSensitiveDataLogging()
#End If
    End Sub

    Protected Overrides Sub OnModelCreating(modelBuilder As ModelBuilder)
        ' Configure decimal precision
        modelBuilder.Entity(Of Country)() _
            .Property(Function(c) c.GDP) _
            .HasPrecision(18, 2)
    End Sub
End Class

Public Class CountryContext
    Inherits DbContext

    Public Property Countries As DbSet(Of Country)

    Protected Overrides Sub OnConfiguring(optionsBuilder As DbContextOptionsBuilder)
        ' Configure SQLite connection
        optionsBuilder.UseSqlite("Data Source=CountryGDP.db")

        ' Enable sensitive data logging in development
#If DEBUG Then
        optionsBuilder.EnableSensitiveDataLogging()
#End If
    End Sub

    Protected Overrides Sub OnModelCreating(modelBuilder As ModelBuilder)
        ' Configure decimal precision
        modelBuilder.Entity(Of Country)() _
            .Property(Function(c) c.GDP) _
            .HasPrecision(18, 2)
    End Sub
End Class

Imports System.Threading.Tasks
Imports IronXL
Imports Microsoft.EntityFrameworkCore

Public Async Function ImportGDPDataAsync() As Task
    Try
        ' Load Excel file
        Dim workBook = WorkBook.Load("Spreadsheets\GDP.xlsx")
        Dim workSheet = workBook.GetWorkSheet("GDPByCountry")

        Using context = New CountryContext()
            ' Ensure database exists
            Await context.Database.EnsureCreatedAsync()

            ' Clear existing data (optional)
            Await context.Database.ExecuteSqlRawAsync("DELETE FROM Countries")

            ' Import data with progress tracking
            Dim totalRows As Integer = 213
            For row As Integer = 2 To totalRows
                ' Read country data
                Dim countryName = workSheet($"A{row}").StringValue
                Dim gdpValue = workSheet($"B{row}").DecimalValue

                ' Skip empty rows
                If String.IsNullOrWhiteSpace(countryName) Then
                    Continue For
                End If

                ' Create and add entity
                Dim country = New Country With {
                    .Name = countryName.Trim(),
                    .GDP = gdpValue * 1_000_000 ' Convert to actual value if in millions
                }

                Await context.Countries.AddAsync(country)

                ' Save in batches for performance
                If row Mod 50 = 0 Then
                    Await context.SaveChangesAsync()
                    Console.WriteLine($"Imported {row - 1} of {totalRows} countries")
                End If
            Next

            ' Save remaining records
            Await context.SaveChangesAsync()
            Console.WriteLine($"Successfully imported {Await context.Countries.CountAsync()} countries")
        End Using
    Catch ex As Exception
        Console.WriteLine($"Import failed: {ex.Message}")
        Throw
    End Try
End Function

Imports System.Threading.Tasks
Imports IronXL
Imports Microsoft.EntityFrameworkCore

Public Async Function ImportGDPDataAsync() As Task
    Try
        ' Load Excel file
        Dim workBook = WorkBook.Load("Spreadsheets\GDP.xlsx")
        Dim workSheet = workBook.GetWorkSheet("GDPByCountry")

        Using context = New CountryContext()
            ' Ensure database exists
            Await context.Database.EnsureCreatedAsync()

            ' Clear existing data (optional)
            Await context.Database.ExecuteSqlRawAsync("DELETE FROM Countries")

            ' Import data with progress tracking
            Dim totalRows As Integer = 213
            For row As Integer = 2 To totalRows
                ' Read country data
                Dim countryName = workSheet($"A{row}").StringValue
                Dim gdpValue = workSheet($"B{row}").DecimalValue

                ' Skip empty rows
                If String.IsNullOrWhiteSpace(countryName) Then
                    Continue For
                End If

                ' Create and add entity
                Dim country = New Country With {
                    .Name = countryName.Trim(),
                    .GDP = gdpValue * 1_000_000 ' Convert to actual value if in millions
                }

                Await context.Countries.AddAsync(country)

                ' Save in batches for performance
                If row Mod 50 = 0 Then
                    Await context.SaveChangesAsync()
                    Console.WriteLine($"Imported {row - 1} of {totalRows} countries")
                End If
            Next

            ' Save remaining records
            Await context.SaveChangesAsync()
            Console.WriteLine($"Successfully imported {Await context.Countries.CountAsync()} countries")
        End Using
    Catch ex As Exception
        Console.WriteLine($"Import failed: {ex.Message}")
        Throw
    End Try
End Function

Imports System
Imports System.Collections.Generic
Imports System.Net.Http
Imports System.Threading.Tasks
Imports Newtonsoft.Json
Imports IronXL

' Define data model matching API response
Public Class RestCountry
    Public Property Name As String
    Public Property Population As Long
    Public Property Region As String
    Public Property NumericCode As String
    Public Property Languages As List(Of Language)
End Class

Public Class Language
    Public Property Name As String
    Public Property NativeName As String
End Class

' Fetch and process API data
Public Async Function ImportCountryDataAsync() As Task
    Using httpClient As New HttpClient()

        Try
            ' Call REST API
            Dim response As String = Await httpClient.GetStringAsync("https://restcountries.com/v3.1/all")
            Dim countries As List(Of RestCountry) = JsonConvert.DeserializeObject(Of List(Of RestCountry))(response)

            ' Create new workbook
            Dim workBook As WorkBook = WorkBook.Create(ExcelFileFormat.XLSX)
            Dim workSheet As WorkSheet = workBook.CreateWorkSheet("Countries")

            ' Add headers with styling
            Dim headers As String() = {"Country", "Population", "Region", "Code", "Language 1", "Language 2", "Language 3"}
            For col As Integer = 0 To headers.Length - 1
                Dim headerCell = workSheet(0, col)
                headerCell.Value = headers(col)
                headerCell.Style.Font.Bold = True
                headerCell.Style.SetBackgroundColor("#366092")
                headerCell.Style.Font.Color = "#FFFFFF"
            Next

            ' Import country data
            Await ProcessCountryData(countries, workSheet)

            ' Save workbook
            workBook.SaveAs("CountriesFromAPI.xlsx")
        Catch ex As Exception
            Console.WriteLine($"API import failed: {ex.Message}")
        End Try

    End Using
End Function

Imports System
Imports System.Collections.Generic
Imports System.Net.Http
Imports System.Threading.Tasks
Imports Newtonsoft.Json
Imports IronXL

' Define data model matching API response
Public Class RestCountry
    Public Property Name As String
    Public Property Population As Long
    Public Property Region As String
    Public Property NumericCode As String
    Public Property Languages As List(Of Language)
End Class

Public Class Language
    Public Property Name As String
    Public Property NativeName As String
End Class

' Fetch and process API data
Public Async Function ImportCountryDataAsync() As Task
    Using httpClient As New HttpClient()

        Try
            ' Call REST API
            Dim response As String = Await httpClient.GetStringAsync("https://restcountries.com/v3.1/all")
            Dim countries As List(Of RestCountry) = JsonConvert.DeserializeObject(Of List(Of RestCountry))(response)

            ' Create new workbook
            Dim workBook As WorkBook = WorkBook.Create(ExcelFileFormat.XLSX)
            Dim workSheet As WorkSheet = workBook.CreateWorkSheet("Countries")

            ' Add headers with styling
            Dim headers As String() = {"Country", "Population", "Region", "Code", "Language 1", "Language 2", "Language 3"}
            For col As Integer = 0 To headers.Length - 1
                Dim headerCell = workSheet(0, col)
                headerCell.Value = headers(col)
                headerCell.Style.Font.Bold = True
                headerCell.Style.SetBackgroundColor("#366092")
                headerCell.Style.Font.Color = "#FFFFFF"
            Next

            ' Import country data
            Await ProcessCountryData(countries, workSheet)

            ' Save workbook
            workBook.SaveAs("CountriesFromAPI.xlsx")
        Catch ex As Exception
            Console.WriteLine($"API import failed: {ex.Message}")
        End Try

    End Using
End Function

Private Async Function ProcessCountryData(countries As List(Of RestCountry), workSheet As WorkSheet) As Task
    For i As Integer = 0 To countries.Count - 1
        Dim country = countries(i)
        Dim row As Integer = i + 1 ' Start from row 1 (after headers)
        
        ' Write basic country data
        workSheet($"A{row}").Value = country.Name
        workSheet($"B{row}").Value = country.Population
        workSheet($"C{row}").Value = country.Region
        workSheet($"D{row}").Value = country.NumericCode
        
        ' Format population with thousands separator
        workSheet($"B{row}").FormatString = "#,##0"
        
        ' Add up to 3 languages
        For langIndex As Integer = 0 To Math.Min(3, If(country.Languages?.Count, 0)) - 1
            Dim language = country.Languages(langIndex)
            Dim columnLetter As String = ChrW(AscW("E"c) + langIndex).ToString()
            workSheet($"{columnLetter}{row}").Value = language.Name
        Next
        
        ' Add conditional formatting for regions
        If country.Region = "Europe" Then
            workSheet($"C{row}").Style.SetBackgroundColor("#E6F3FF")
        ElseIf country.Region = "Asia" Then
            workSheet($"C{row}").Style.SetBackgroundColor("#FFF2E6")
        End If
        
        ' Show progress every 50 countries
        If i Mod 50 = 0 Then
            Console.WriteLine($"Processed {i} of {countries.Count} countries")
        End If
    Next
    
    ' Auto-size all columns
    For col As Integer = 0 To 6
        workSheet.AutoSizeColumn(col)
    Next
End Function

Private Async Function ProcessCountryData(countries As List(Of RestCountry), workSheet As WorkSheet) As Task
    For i As Integer = 0 To countries.Count - 1
        Dim country = countries(i)
        Dim row As Integer = i + 1 ' Start from row 1 (after headers)
        
        ' Write basic country data
        workSheet($"A{row}").Value = country.Name
        workSheet($"B{row}").Value = country.Population
        workSheet($"C{row}").Value = country.Region
        workSheet($"D{row}").Value = country.NumericCode
        
        ' Format population with thousands separator
        workSheet($"B{row}").FormatString = "#,##0"
        
        ' Add up to 3 languages
        For langIndex As Integer = 0 To Math.Min(3, If(country.Languages?.Count, 0)) - 1
            Dim language = country.Languages(langIndex)
            Dim columnLetter As String = ChrW(AscW("E"c) + langIndex).ToString()
            workSheet($"{columnLetter}{row}").Value = language.Name
        Next
        
        ' Add conditional formatting for regions
        If country.Region = "Europe" Then
            workSheet($"C{row}").Style.SetBackgroundColor("#E6F3FF")
        ElseIf country.Region = "Asia" Then
            workSheet($"C{row}").Style.SetBackgroundColor("#FFF2E6")
        End If
        
        ' Show progress every 50 countries
        If i Mod 50 = 0 Then
            Console.WriteLine($"Processed {i} of {countries.Count} countries")
        End If
    Next
    
    ' Auto-size all columns
    For col As Integer = 0 To 6
        workSheet.AutoSizeColumn(col)
    Next
End Function

Dim cell = sheet("B5")
If Not cell.IsEmpty Then
    total += cell.DecimalValue
End If

Dim cell = sheet("B5")
If Not cell.IsEmpty Then
    total += cell.DecimalValue
End If

' What you probably want:
Dim birthday As DateTime = sheet("E2").DateTimeValue

' What gives you "45292":
Dim birthday As String = sheet("E2").StringValue

' What you probably want:
Dim birthday As DateTime = sheet("E2").DateTimeValue

' What gives you "45292":
Dim birthday As String = sheet("E2").StringValue

Imports System
Imports System.Diagnostics
Imports IronXL

License.LicenseKey = Environment.GetEnvironmentVariable("IRONXL_LICENSE_KEY")

Dim sw As Stopwatch = Stopwatch.StartNew()
Dim workbook = WorkBook.Load("GDP.xlsx")
Dim sum As Decimal = workbook.WorkSheets.First()("B2:B214").Sum()
sw.Stop()
Console.WriteLine($"cold: {sw.Elapsed.TotalMilliseconds:F1} ms")

Imports System
Imports System.Diagnostics
Imports IronXL

License.LicenseKey = Environment.GetEnvironmentVariable("IRONXL_LICENSE_KEY")

Dim sw As Stopwatch = Stopwatch.StartNew()
Dim workbook = WorkBook.Load("GDP.xlsx")
Dim sum As Decimal = workbook.WorkSheets.First()("B2:B214").Sum()
sw.Stop()
Console.WriteLine($"cold: {sw.Elapsed.TotalMilliseconds:F1} ms")