The sample demonstrates how to convert Excel workbook to HTML file via Spire.XLS.

using Spire.Xls;

namespace ToHtml
{
    class Program
    {
        static void Main(string[] args)
        {
            Workbook workbook = new Workbook();
            workbook.LoadFromFile(@"..\..\..\..\Data\vendors.xls",ExcelVersion.Version97to2003);
            Worksheet sheet = workbook.Worksheets[0];

            sheet.SaveToHtml("sample.html");
            System.Diagnostics.Process.Start("sample.html");
        }
    }
}

Imports Spire.Xls

Namespace ToHtml
	Friend Class Program
		Shared Sub Main(ByVal args() As String)
			Dim workbook As New Workbook()
			workbook.LoadFromFile("..\..\..\..\Data\vendors.xls",ExcelVersion.Version97to2003)
			Dim sheet As Worksheet = workbook.Worksheets(0)

			sheet.SaveToHtml("sample.html")
			System.Diagnostics.Process.Start("sample.html")
		End Sub
	End Class
End Namespace