Convert CSV to Excel or XLSX/XLS to CSV with C# VB.NET

CSVtoExcel.cs

// Opening CSV Files
// Creating CSV LoadOptions object
LoadOptions loadOptions = new LoadOptions(LoadFormat.CSV);
// Creating an Workbook object with CSV file path and the loadOptions
// object
Workbook workbook = new Workbook(dataDir + "Sample.csv", loadOptions);
workbook.Save(dataDir + "CSVtoExcel.xlsx", SaveFormat.Xlsx);

ExcelToCSV.cs

// Load the input Excel file
Workbook workbook = new Workbook(dataDir + "CSVtoExcel.xlsx");

// Save output CSV file
workbook.Save(dataDir + "ExcelToCSV.csv", SaveFormat.CSV);