How to convert xls document to xlsx format document?

9 May 20242 minutes to read

The following code illustrates how to convert xls document to xlsx format document.

C# [Cross-platform]

using (ExcelEngine excelEngine = new ExcelEngine())
{
    IApplication application = excelEngine.Excel;
    application.DefaultVersion = ExcelVersion.Xlsx;
    
    //Loads an xls file
    FileStream fileStream = new FileStream("InputTemplate.xls", FileMode.Open, FileAccess.Read);
    IWorkbook workbook = application.Workbooks.Open(fileStream);

    //Set the workbook version to xlsx
    workbook.Version = ExcelVersion.Xlsx;
    
    //Saving the workbook as stream in xlsx format
    FileStream stream = new FileStream("Output.xlsx", FileMode.Create, FileAccess.ReadWrite);
    workbook.SaveAs(stream);
    stream.Dispose();
}

C# [Windows-specific]

using (ExcelEngine engine = new ExcelEngine())
{
    IApplication application = engine.Excel;
    application.DefaultVersion = ExcelVersion.Xlsx;

    //Loads an xls file
    IWorkbook workbook = application.Workbooks.Open("InputTemplate.xls");

    //Set the workbook version to xlsx
    workbook.Version = ExcelVersion.Xlsx;

    //Saving the workbook in xlsx format
    workbook.SaveAs("Output.xlsx");
}

VB.NET [Windows-specific]

Using engine As ExcelEngine = New ExcelEngine()
    Dim application As IApplication = engine.Excel
    application.DefaultVersion = ExcelVersion.Xlsx

    'Loads an xls file
    Dim workbook As IWorkbook = application.Workbooks.Open("InputTemplate.xls")

    'Set the workbook version to xlsx
    workbook.Version = ExcelVersion.Xlsx;

    'Saving the workbook in xlsx format
    workbook.SaveAs("Output.xlsx")
End Using