Streaming the file from memory

The users have requested the option to "generate" an excel  file representation of GridView contents.
Does anyone know how to do this without saving the file to the server but rather just streaming it to the user from memory?


My below code is working
I just need help in streaming directly from memory instead of using physical path of server machine  then saving the file on client machine







Private Sub generateExcelSheet()
        Try
            Dim weekFrom As String = DdFromWeek.SelectedValue
            Dim weekTo As String = DdToWeek.SelectedValue

            Dim sql As String = "SELECT distinct[Wk_no] FROM [Nd] WHERE [Wk_no] BETWEEN '" ...