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Utility Belt:
HttpPost
by Gary Pupurs
HttpGrab() is great when
you want to screen scrape a URL you've seen in the browser's location box.
But what about POSTs? How do you screen scrape when you need to submit a
remote form via ASP.NET?
Fortunately, Utility Belt also makes
this easy!
The code below shows "Utility Belt"
submitting form parameters to a third party server, based on the form fields on
your page. The result of the form POST is captured and returned as a
string. Easy!
Tips on building your custom
form:
-
On the remote form you want to
scrape, do a 'View Source' and cut/paste the code to a page on your server.
-
Pare it down to the basic elements
between the <FORM> </FORM> tags.
-
Save as a plain HTML file and try
to submit the form.
-
Keep removing non-essential form
elements and retest until you find the minimum fields for your desired
results.
-
Then build your ASP.NET form with
similar elements, using hidden form elements for any required but non-changing
fields.
Note: Some servers may use
Javascript, redirection, HTTP header checks or other methods to defeat form
submissions from servers other than their own. You might be able to get
around these with some ingenuity. Or you may not. YMMV.
filename=/experiments/utilitybelt/vercurrent/ubdemo_httppost.aspx
<%@ Debug="true" %>
<%@ Assembly Src="utilitybelt.vb" %>
<script runat="server">
Dim ub as New learnasp.UtilityBelt()
Sub Page_Load(Src As Object, E As EventArgs)
If IsPostback
dim ht1 as new hashtable
ht1.add("searchtext",txtSearch.Text)
ht1.add("searchdatabase",rblNewsSource.SelectedItem.Value)
lblResults.Text = ub.HttpPost("http://www.washingtonpost.com/cgi-bin/search99.pl",ht1)
End If
End Sub
</script>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>HttpPost demo</title>
</head>
<body>
<form runat="server">
<h1>Utility Belt HttpPost() Demo</h1>
Enter a word or phrase to search for headlines:<br>
<asp:textbox id="txtSearch" Columns="40" runat="server" />
<br>
<asp:RadioButtonList id="rblNewsSource" runat="server">
<asp:ListItem value="ap">Associated Press</asp:ListItem>
<asp:ListItem value="reut">Reuters</asp:ListItem>
</asp:RadioButtonList>
<br>
<input type="submit" value="Do that ASP.NET magic!" />
<hr>
<p>
Results:<br>
<asp:label id="lblResults" runat="server" />
<hr>
<asp:placeholder id="phExceptionInfo" runat="server" />
</form>
</body>
</html>
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