[Solved] Empty cells skipped (ignored) while reading data from Excel to DataTable in ClosedXML

adding (1, dt.Columns.Count) did the trick.

protected void ImportExcel(object sender, EventArgs e)
{
    //Save the uploaded Excel file.
    string filePath = Server.MapPath("~/Files/") + Path.GetFileName(FileUpload1.PostedFile.FileName);
    FileUpload1.SaveAs(filePath);

    //Open the Excel file using ClosedXML.
    using (XLWorkbook workBook = new XLWorkbook(filePath))
    {
        //Read the first Sheet from Excel file.
        IXLWorksheet workSheet = workBook.Worksheet(1);

        //Create a new DataTable.
        DataTable dt = new DataTable();

        //Loop through the Worksheet rows.
        bool firstRow = true;
        foreach (IXLRow row in workSheet.Rows())
        {
            //Use the first row to add columns to DataTable.
            if (firstRow)
            {
                foreach (IXLCell cell in row.Cells())
                {
                    dt.Columns.Add(cell.Value.ToString());
                }
                firstRow = false;
            }
            else
            {
                //Add rows to DataTable.
                dt.Rows.Add();
                int i = 0;
                foreach (IXLCell cell in row.Cells(1, dt.Columns.Count))
                {
                    dt.Rows[dt.Rows.Count - 1][i] = cell.Value.ToString();
                    i++;
                }
            }

            GridView1.DataSource = dt;
            GridView1.DataBind();
        }
    }
}

Protected Sub ImportExcel(sender As Object, e As EventArgs)
    'Save the uploaded Excel file.
    Dim filePath As String = Server.MapPath("~/Files/") + Path.GetFileName(FileUpload1.PostedFile.FileName)
    FileUpload1.SaveAs(filePath)

    'Open the Excel file using ClosedXML.
    Using workBook As New XLWorkbook(filePath)
        'Read the first Sheet from Excel file.
        Dim workSheet As IXLWorksheet = workBook.Worksheet(1)

        'Create a new DataTable.
        Dim dt As New DataTable()

        'Loop through the Worksheet rows.
        Dim firstRow As Boolean = True
        For Each row As IXLRow In workSheet.Rows()
            'Use the first row to add columns to DataTable.
            If firstRow Then
                For Each cell As IXLCell In row.Cells()
                    dt.Columns.Add(cell.Value.ToString())
                Next
                firstRow = False
            Else
                'Add rows to DataTable.
                dt.Rows.Add()
                Dim i As Integer = 0
                For Each cell As IXLCell In row.Cells(1, dt.Columns.Count)
                    dt.Rows(dt.Rows.Count - 1)(i) = cell.Value.ToString()
                    i += 1
                Next
            End If

            GridView1.DataSource = dt
            GridView1.DataBind()
        Next
    End Using
End Sub