questo è asp classico / vbscript, ma non farai assolutamente alcuna fatica a riportarlo in .net

codice:
ExcelFile = "C:\Cartella\foglio.xls"

Set ExcelConnection = Server.createobject("ADODB.Connection") 
ExcelConnection.Open "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & ExcelFile & ";Extended Properties=""Excel 12.0 Xml;HDR=YES;IMEX=1"";"

SET ExcelRS = Server.CreateObject("ADODB.Recordset") 
ExcelSQL = "SELECT * FROM [NomeTab$] ORDER BY ColonnaCheVuoiTu" 
ExcelRS.Open ExcelSQL, ExcelConnection

Do While Not ExcelRS.EOF 
	Response.Write ExcelRS("nomecolonna")
	ExcelRS.MoveNext
Loop


ExcelRS.Close()
Set ExcelRS = Nothing


ExcelConnection.Close()
Set ExcelConnection = Nothing