A Comparison of IronXL and NPOI

using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
using System.Data;
using System.IO;
using System.Collections.Generic;

Imports NPOI.SS.UserModel
Imports NPOI.XSSF.UserModel
Imports System.Data
Imports System.IO
Imports System.Collections.Generic

public void ReadExcelNPOI()
{
    DataTable dtTable = new DataTable();
    List<string> lstRows = new List<string>();
    ISheet objWorksheet;
    string strPath = @"c:\temp\NPOI_Test.XLSX";

    // Use FileStream to open the Excel file
    using (var fStream = new FileStream(strPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
    {
        fStream.Position = 0;
        XSSFWorkbook objWorkbook = new XSSFWorkbook(fStream);
        objWorksheet = objWorkbook.GetSheetAt(0);
        IRow objHeader = objWorksheet.GetRow(0);
        int countCells = objHeader.LastCellNum;

        // Add columns to the DataTable based on the header row of Excel
        for (int j = 0; j < countCells; j++)
        {
            ICell objCell = objHeader.GetCell(j);
            if (objCell == null || string.IsNullOrWhiteSpace(objCell.ToString())) continue;
            {
                dtTable.Columns.Add(objCell.ToString());
            }
        }

        // Add rows to the DataTable, looping through each row and cell
        for (int i = (objWorksheet.FirstRowNum + 1); i <= objWorksheet.LastRowNum; i++)
        {
            IRow objRow = objWorksheet.GetRow(i);
            if (objRow == null || objRow.Cells.All(d => d.CellType == CellType.Blank)) continue;

            for (int j = objRow.FirstCellNum; j < countCells; j++)
            {
                ICell cell = objRow.GetCell(j);
                if (cell != null && !string.IsNullOrEmpty(cell.ToString()) && !string.IsNullOrWhiteSpace(cell.ToString()))
                {
                    lstRows.Add(cell.ToString());
                }
            }

            if (lstRows.Count > 0)
                dtTable.Rows.Add(lstRows.ToArray());

            lstRows.Clear();
        }
    }

    // Assuming dataGridView1 is a DataGridView control on a Form
    dataGridView1.DataSource = dtTable;
}

private void button1_Click(object sender, EventArgs e)
{
    ReadExcelNPOI();
}

Public Sub ReadExcelNPOI()
	Dim dtTable As New DataTable()
	Dim lstRows As New List(Of String)()
	Dim objWorksheet As ISheet
	Dim strPath As String = "c:\temp\NPOI_Test.XLSX"

	' Use FileStream to open the Excel file
	Using fStream = New FileStream(strPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)
		fStream.Position = 0
		Dim objWorkbook As New XSSFWorkbook(fStream)
		objWorksheet = objWorkbook.GetSheetAt(0)
		Dim objHeader As IRow = objWorksheet.GetRow(0)
		Dim countCells As Integer = objHeader.LastCellNum

		' Add columns to the DataTable based on the header row of Excel
		For j As Integer = 0 To countCells - 1
			Dim objCell As ICell = objHeader.GetCell(j)
			If objCell Is Nothing OrElse String.IsNullOrWhiteSpace(DirectCast(objCell, Object).ToString()) Then
				Continue For
			End If
			If True Then
				dtTable.Columns.Add(DirectCast(objCell, Object).ToString())
			End If
		Next j

		' Add rows to the DataTable, looping through each row and cell
		For i As Integer = (objWorksheet.FirstRowNum + 1) To objWorksheet.LastRowNum
			Dim objRow As IRow = objWorksheet.GetRow(i)
			If objRow Is Nothing OrElse objRow.Cells.All(Function(d) d.CellType = CellType.Blank) Then
				Continue For
			End If

			For j As Integer = objRow.FirstCellNum To countCells - 1
				Dim cell As ICell = objRow.GetCell(j)
				If cell IsNot Nothing AndAlso Not String.IsNullOrEmpty(DirectCast(cell, Object).ToString()) AndAlso Not String.IsNullOrWhiteSpace(DirectCast(cell, Object).ToString()) Then
					lstRows.Add(DirectCast(cell, Object).ToString())
				End If
			Next j

			If lstRows.Count > 0 Then
				dtTable.Rows.Add(lstRows.ToArray())
			End If

			lstRows.Clear()
		Next i
	End Using

	' Assuming dataGridView1 is a DataGridView control on a Form
	dataGridView1.DataSource = dtTable
End Sub

Private Sub button1_Click(ByVal sender As Object, ByVal e As EventArgs)
	ReadExcelNPOI()
End Sub

using IronXL;
using System.Data;

Imports IronXL
Imports System.Data

private void button2_Click(object sender, EventArgs e)
{
    // Load the Excel workbook
    string strPath = @"c:\temp\NPOI_Test.XLSX";
    WorkBook workbook = WorkBook.Load(strPath);

    // Access the default worksheet
    WorkSheet sheet = workbook.DefaultWorkSheet;

    // Convert the worksheet to a DataTable
    var dtTable = sheet.ToDataTable(true);

    // Assuming dataGridView1 is a DataGridView control on a Form
    dataGridView1.DataSource = dtTable;
}

Private Sub button2_Click(ByVal sender As Object, ByVal e As EventArgs)
	' Load the Excel workbook
	Dim strPath As String = "c:\temp\NPOI_Test.XLSX"
	Dim workbook As WorkBook = WorkBook.Load(strPath)

	' Access the default worksheet
	Dim sheet As WorkSheet = workbook.DefaultWorkSheet

	' Convert the worksheet to a DataTable
	Dim dtTable = sheet.ToDataTable(True)

	' Assuming dataGridView1 is a DataGridView control on a Form
	dataGridView1.DataSource = dtTable
End Sub