asp.net vb stream file from page request - asp.net

Question

I am trying to have a dynamically created csv file be the response to a page request. I have the code to create a file that can be downloaded by the client, but that isn't the solution. I have found code that can stream a file but the file seems to have to exist on the file system and I would rather not have to use a temp file if I can help it.
Here is what i have:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim csvTable As DataTable = pointsTable_Select_By_playerName_for_CSV()
Dim sb = New StringBuilder
For Each dcol As DataColumn In csvTable.Columns
sb.Append(dcol.ColumnName & ",")
Next
sb.Append(ControlChars.NewLine)
For Each drow As DataRow In csvTable.Rows
For i As Integer = 0 To csvTable.Columns.Count - 1
sb.Append(drow.Item(i).ToString & ",")
Next
sb.Append(ControlChars.NewLine)
Next
Response.Clear()
Response.ContentType = "text/csv"
Response.AppendHeader("Content-Disposition",
String.Format("attachment; filename={0}.csv", DateTime.Now))
Response.Write(sb.ToString)
Context.Response.End()
End Sub
And the code I found to stream a file:
'Create a stream for the file
Dim stream As Stream = Nothing
'This controls how many bytes to read at a time and send to the client
Dim bytesToRead As Integer = 10000
' Buffer to read bytes in chunk size specified above
Dim buffer As Byte() = New [Byte](bytesToRead - 1) {}
' The number of bytes read
Try
'Create a WebRequest to get the file
Dim fileReq As HttpWebRequest = DirectCast(HttpWebRequest.Create(url), HttpWebRequest)
'Create a response for this request
Dim fileResp As HttpWebResponse = DirectCast(fileReq.GetResponse(), HttpWebResponse)
If fileReq.ContentLength > 0 Then
fileResp.ContentLength = fileReq.ContentLength
End If
'Get the Stream returned from the response
stream = fileResp.GetResponseStream()
' prepare the response to the client. resp is the client Response
Dim resp = HttpContext.Current.Response
'Indicate the type of data being sent
resp.ContentType = "application/octet-stream"
'Name the file
resp.AddHeader("Content-Disposition", String.Format("attachment; filename={0}.csv", DateTime.Now))
resp.AddHeader("Content-Length", fileResp.ContentLength.ToString())
Dim length As Integer
Do
' Verify that the client is connected.
If resp.IsClientConnected Then
' Read data into the buffer.
length = stream.Read(buffer, 0, bytesToRead)
' and write it out to the response's output stream
resp.OutputStream.Write(buffer, 0, length)
' Flush the data
resp.Flush()
'Clear the buffer
buffer = New [Byte](bytesToRead - 1) {}
Else
' cancel the download if client has disconnected
length = -1
End If
'Repeat until no data is read
Loop While length > 0
Finally
If stream IsNot Nothing Then
'Close the input stream
stream.Close()
End If
End Try
The problem is that this code needs to point to a file, is there a way I can use a stream to move the string from sb to the httpresponse?

Answer 1

You can use use Response.Write().
Additionally, If your data might contain , you should be escaping it by placing inside a text qualifier like ".
You also can not use Date Time as the File Name unless you remove special characters from it.
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim FileName As String = (From C In DateTime.Now.ToString()
Where Char.IsLetterOrDigit(C)) & ".csv"
Response.Clear()
Response.ContentType = "text/csv"
Response.AppendHeader("Content-Disposition",
String.Format("attachment; filename={0}.csv", filename)
Dim csvTable As DataTable = pointsTable_Select_By_playerName_for_CSV()
For Each dcol As DataColumn In csvTable.Columns
Response.Write(dcol.ColumnName & ",")
Next
Response.Write(ControlChars.NewLine)
For Each drow As DataRow In csvTable.Rows
Response.Write(String.Join(",", row.ItemArray()) & VbNewLine)
Next
Response.End()
End Sub