string inputFileName = "input.xlsx";
            if (!File.Exists(inputFileName))
            {
                throw new FileNotFoundException(String.Format("File {0} was not found!", inputFileName));
            }

            Telerik.Windows.Documents.Spreadsheet.Model.Workbook workbook;
            IWorkbookFormatProvider formatProvider = new Telerik.Windows.Documents.Spreadsheet.FormatProviders.OpenXml.Xlsx.XlsxFormatProvider();

            using (Stream input = new FileStream(inputFileName, FileMode.Open))
            { 
                workbook = formatProvider.Import(input, TimeSpan.MaxValue);
            }
            string outputFilePath = "output.xlsx";

            using (Stream output = new FileStream(outputFilePath, FileMode.Create))
            {
                formatProvider.Export(workbook, output, TimeSpan.MaxValue);
            }
            Process.Start(new ProcessStartInfo() { FileName = outputFilePath, UseShellExecute = true });

<?xml version="1.0" encoding="utf-8"?>
<workbook xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
	<sheets>
		<sheet sheetId="1" name="Sheet1" state="visible" r:id="rId1" />
	</sheets>
	<definedNames>
		<definedName name="Print_Titles" localSheetId="0" hidden="false">Sheet1!$A$1:$IV$3</definedName>
		<definedName name="_xlnm.Print_Area" localSheetId="0" hidden="false">Sheet1!$A:$G</definedName>
		<definedName name="_xlnm.Print_Titles" localSheetId="0" hidden="false">Sheet1!$1:$3</definedName>
	</definedNames>
</workbook>

var usedCellRange = workbook.ActiveWorksheet.GetUsedCellRange(
    CellPropertyDefinitions.AllPropertyDefinitions
    .Except(
        CellPropertyDefinitions.AllPropertyDefinitions.Where(p => p.Name == "DataValidationRule" || p.Name == "ConditionalFormatting")));

            string fileName = "file.xlsm"; 
            Telerik.Windows.Documents.Spreadsheet.Model.Workbook workbook;
            IWorkbookFormatProvider formatProvider = new Telerik.Windows.Documents.Spreadsheet.FormatProviders.OpenXml.Xlsm.XlsmFormatProvider();

            using (Stream input = new FileStream(fileName, FileMode.Open))
            {
                workbook = formatProvider.Import(input);
            }