Try
Dim wb As HSSFWorkbook = Nothing
Using fs As New FileStream("FilePath", FileMode.Open, FileAccess.Read)
wb = New HSSFWorkbook(fs, True)
End Using
Dim sht As HSSFSheet = wb.GetSheetAt(0)
Dim bs As HSSFCellStyle = GetThinBDRStyle(wb)
For iRow As Integer = 0 To 10
With sht.CreateRow(iRow).CreateCell(0).SetCellValue("AAA")
.CreateCell(1).SetCellValue("BBB")
.CreateCell(2).SetCellValue("CCC")
'CellBorder
.GetCell(0).CellStyle = bs.GetCell(1).CellStyle = bs
.GetCell(2).CellStyle = bs
End With
Next
Using fs As New FileStream("SavePath", FileMode.OpenOrCreate, FileAccess.Write)
wb.Write(fs)
End Using
Catch ex As Exception
End Try
End Sub
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Private Function GetThinBDRStyle(WB As HSSFWorkbook) As HSSFCellStyle
Dim style As HSSFCellStyle = WB.CreateCellStyle()
style.BorderTop = BorderStyle.THIN
style.BorderRight = BorderStyle.THIN
style.BorderLeft = BorderStyle.THIN
style.BorderBottom = BorderStyle.THIN
Return style
End Function