Search for values in between two values in a string?

13 May 2009 5:13 AM

pat

The subject may not be written well but what I'm trying to do is
search for a value in a string by searching for its span class. The
string is an HTML file so what I want is the value in between and 

Is there anything in vb.net that can do that? c#.net has a function,
but I can't seem to find it in vb.net. Thanks

13 May 2009 7:41 AM

Mike

pat wrote:

> The subject may not be written well but what I'm trying to do is
> search for a value in a string by searching for its span class. The
> string is an HTML file so what I want is the value in between class="myclass"> and 
>
> Is there anything in vb.net that can do that? c#.net has a function,
> but I can't seem to find it in vb.net. Thanks

You can use XPATH or LINQ to perform XML or HTML lookups. I'm not
familar with LINQ and I believe its for .NET 3.0 with I haven't
upgraded to yet. But in XPATH, its fairly simple;

Example HTML file:


<html>
<body>
text
text1
text2
text2.2
text2.3
text2.4
text3
text4
text5
</body>
</html>

Using XPATH VB.NET Example:

Imports System.XML.XPath

Class Test_Xpath

 '' load xml doc, query and return values array
 Shared Function GetHtmlValue( _
 ByVal xpq As String, _
 ByVal xmlfn As String) As String()
 Dim xmldoc As New XPathDocument(xmlfn)
 Dim nav As XPathNavigator = xmldoc.CreateNavigator()
 Dim iterator As XPathNodeIterator
 Dim result As New List(Of String)
 Try
 iterator = nav.Select(xpq)
 Do While iterator.MoveNext
 result.Add(iterator.Current.Value)
 Loop
 Catch ex As Exception
 End Try
 Return result.ToArray()
 End Function

 Shared Sub DoTest1(byval query as string, byval fn as string)
 Dim res As String() = GetHtmlValue(query, fn)
 Console.WriteLine("Total DOM elements Found: {0}", res.Length)
 For Each s As String In res
 Console.WriteLine("{0}", s)
 Next
 Console.ReadKey(True)
 End Sub

 Shared Sub main()

 ' expecting one
 DoTest1("//child::*/span[@class='myclass']", "c:\spantest.htm")

 ' expecting multiple
 DoTest1("//child::*/span[@class='myclass2']","c:\spantest.htm")

 ' expecting none
 DoTest1("//child::*/span[@class='myclassXX']","c:\spantest.htm")

 End Sub
End Class

Of course, learning XPATH statements is the trick. It is well
documented in MSDN.

--

13 May 2009 7:33 PM

Herfried K. Wagner [MVP]

"Mike" <unkn***@unknown.tv> schrieb:
>> The subject may not be written well but what I'm trying to do is
>> search for a value in a string by searching for its span class. The
>> string is an HTML file so what I want is the value in between > class="myclass"> and 
>>
>> Is there anything in vb.net that can do that? c#.net has a function,
>> but I can't seem to find it in vb.net. Thanks
>
> You can use XPATH or LINQ to perform XML or HTML lookups. I'm not
> familar with LINQ and I believe its for .NET 3.0 with I haven't upgraded
> to yet. But in XPATH, its fairly simple;

Note that this will only work with XHTML or HTML which is "compatible" to
XHTML, but it will not work with every HTML document. For the latter, using
an SGML parser might be an option.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://dotnet.mvps.org/dotnet/faqs/>