How to export list(of entity) to text file

Using n-tire architecture and getting values
PresentationLayer:
Dim objBLayer As New BuisnessLayer()
Datagridview1.datasource = objBLayer.getDetails(startDt, endDt, 1)
instead of binding to datagridview....i want to export data to text file.... any help would be appreciated!
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BusinessLayer:
Dim objDal As New Dal()
Public Function getDetails(ByVal startdate As Date, ByVal enddate As Date, ByVal intvalue As Integer) As List(Of Entity)      Return objDal.getDetails(startdate, enddate, intvalue) End Function
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DataAccessLayer
Public Function getDetails(ByVal startdate As Date, ByVal enddate As Date, ByVal intvalue As Integer) As List(Of Entity) Dim objDetails As New List(Of Entity)() Try
some code.........
While dr.Read() Dim obj ...