Here Mudassar Ahmed Khan has explained with an example, how to read Excel File (xls & xlsx) data in ASP.Net using C# and VB.Net.
When the Excel file is uploaded, the Excel File data is available in the InputStream property of the FileUpload control.
Using ClosedXml library, the Excel file data can be easily read from the InputStream property and displayed on Web Page using GridView in ASP.Net using C# and VB.Net.