Gray Wolf Blog

This is a very simple function for extracting any ASP .Net page state value such as __VIEWSTATE or __EVENTVALIDATION. These values are necessary when scraping some websites.

1. Public Shared Function ExtractDotNetData(ByVal strData As String, ByVal strStateName As String, ByVal strDelimiter As String) As String
2.  
3. Dim iStateNamePosition As Integer = strData.IndexOf(strStateName)
4. If iStateNamePosition < 0 Then Return ""
5.  
6. Dim iStateValuePosition As Integer = strData.IndexOf(strDelimiter, iStateNamePosition)
7. If iStateValuePosition < 0 Then Return ""
8.  
9. Dim iStateStartPosition As Integer = iStateValuePosition + strDelimiter.Length
10. Dim iStateEndPosition As Integer = strData.IndexOf("""", iStateStartPosition)
11.  
12. Return HttpUtility.UrlEncodeUnicode(strData.Substring(iStateStartPosition, iStateEndPosition - iStateStartPosition))
13. End Function
14.  
15. strViewState = ExtractDotNetData(strResponseData, "__VIEWSTATE", "value=""")
16. strEventValidation = ExtractDotNetData(strResponseData, "__EVENTVALIDATION", "value=""")
17. Download this code: ExtractDotNetData.txt