This code-tip I discovered while developing a webservice to
"screen scrape" a webpage to determine if a certain text phrase was
present. Regular expressions are best suited for achieving this task;
however, they are not the easiest to learn.
The System.Text.RegularExpressions namespace in
.NET 2.0 has a handy function called IsMatch that achieves what I wanted. The
code snippet below accepts two arguments (the URL to monitor, the Text to
search for), makes an HTTP request and reads the webpage into a stream.
The stream is searched for the text passed into the method. The one thing I
discovered while using the 'IsMatch' method is that the text is case and space
sensitive. For example, if you are searching "http://www.iislogs.com"
for text in the title of the page, searching for "IIS Logs -" is the
exact phrase that would be searched for.
Listing 1
Public Function URLListed(ByVal URL As String, ByValstrArgument As String) As String
Dim blnListed As String
blnListed = readWebPage(URL, strArgument)
Return blnListed
End Function
Private Function readWebPage(ByVal strSource As String, ByVal strArgument AsString) As String
Dim strLine As String
Dim objSR As System.IO.StreamReader = Nothing
Dim objResponse As WebResponse = Nothing
Dim objRequest As WebRequest =System.Net.HttpWebRequest.Create(strSource)
Try
objResponse = objRequest.GetResponse
objSR = NewSystem.IO.StreamReader(objResponse.GetResponseStream(),System.Text.Encoding.ASCII)
Do While objSR.EndOfStream = False
strLine = objSR.ReadLine()
If Regex.IsMatch(strLine, strArgument) Then
Return "Listed"
Exit Function
End If
Loop
objSR.Close()
objResponse.Close()
Return "Not Listed"
Catch f As Exception
Return "Error:" &f.Message.ToString()
End Try
End Function
Conclusion
I hope this example helps in your Regular Expressions
adventure. Happy coding!
Resources
Regular Expression Library
Regular Expression Advice
