Capturing the HTML from an ASP.NET 2.0 page

Ken Cox - Microsoft MVP

I'm trying to find a way to program in ASP.NET 2.0 but capture the HTML
output. I found the following routine in ASP.NET 2.0 Cookbook from O'Reilly.
It doesn't work if I include a server-side dropdownlist control on the page.
The error is RegisterForEven tValidation can only be called during Render();

Any ideas?

Ken
Microsoft MVP [ASP.NET]
<%@ Page Language="VB" %>

<script runat="server">
Protected Sub Page_Load _
(ByVal sender As Object, _
ByVal e As System.EventArg s) Handles Me.Load
Const OUTPUT_FILENAME As String = "renderedpage.h tml"
Dim renderedOutput As StringBuilder = Nothing
Dim strWriter As IO.StringWriter = Nothing
Dim tWriter As HtmlTextWriter = Nothing
Dim outputStream As IO.FileStream = Nothing
Dim sWriter As IO.StreamWriter = Nothing
Dim filename As String
Dim nextPage As String

Try
'create a HtmlTextWriter to use for rendering the page
renderedOutput = New StringBuilder
strWriter = New IO.StringWriter (renderedOutput )
tWriter = New HtmlTextWriter( strWriter)

'render the page output
Page.RenderCont rol(tWriter)

'save the rendered output to a file
filename = Server.MapPath( ".") & "\" & OUTPUT_FILENAME
outputStream = New IO.FileStream(f ilename, _
IO.FileMode.Cre ate)
sWriter = New IO.StreamWriter (outputStream)
sWriter.Write(r enderedOutput.T oString())
sWriter.Flush()

'redirect to another page
'NOTE: Continuing with the display of this page will result in
the
' page being rendered a second time which will cause an
exception
' to be thrown
nextPage = "DisplayMessage .aspx?" & _
"PageHeader=Inf ormation" & "&" & _
"Message1=H TML Output Saved To " & OUTPUT_FILENAME
Response.Redire ct(nextPage)

Finally
'clean up
If (Not IsNothing(outpu tStream)) Then
outputStream.Cl ose()
End If

If (Not IsNothing(tWrit er)) Then
tWriter.Close()
End If

If (Not IsNothing(strWr iter)) Then
strWriter.Close ()
End If
End Try
End Sub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Captur e Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:dropdownli st id="DropDownLis t1" runat="server">
<asp:listitem>r ed</asp:listitem>
<asp:listitem>b lue</asp:listitem>
<asp:listitem>g reen</asp:listitem>
</asp:dropdownlis t></div>
</form>
</body>
</html>

Feb 12 '06 #1

Subscribe Reply

1711

Teemu Keiski

I responded already on Forums, but here's for reference
**
Hello,

it complained for me about event validation , so when disabling it with
EnableEventVali dation="False" helped. But, if you try it this way e.g moving
the code to overridden Render method

<%@ Page Language="VB" %>

<script runat="server">

Protected Overrides Sub Render(ByVal writer As
System.Web.UI.H tmlTextWriter)
Const OUTPUT_FILENAME As String = "renderedpage.h tml"
Dim renderedOutput As StringBuilder = Nothing
Dim strWriter As IO.StringWriter = Nothing
Dim tWriter As HtmlTextWriter = Nothing
Dim outputStream As IO.FileStream = Nothing
Dim sWriter As IO.StreamWriter = Nothing
Dim filename As String
Dim nextPage As String

Try
'create a HtmlTextWriter to use for rendering the page
renderedOutput = New StringBuilder
strWriter = New IO.StringWriter (renderedOutput )
tWriter = New HtmlTextWriter( strWriter)

MyBase.Render(t Writer)

'save the rendered output to a file
filename = Server.MapPath( ".") & "\" & OUTPUT_FILENAME
outputStream = New IO.FileStream(f ilename, _
IO.FileMode.Cre ate)
sWriter = New IO.StreamWriter (outputStream)
sWriter.Write(r enderedOutput.T oString())
sWriter.Flush()

' redirect to another page
' NOTE: Continuing with the display of this page will result in
the
' page being rendered a second time which will cause an
exception
' to be thrown
nextPage = "DisplayMessage .aspx?" & _
"PageHeader=Inf ormation" & "&" & _
"Message1=H TML Output Saved To " & OUTPUT_FILENAME
'Response.Redir ect(nextPage)
'Response.Write (renderedOutput .ToString())

writer.Write(re nderedOutput.To String())
Finally

'clean up
If (Not IsNothing(outpu tStream)) Then
outputStream.Cl ose()
End If

If (Not IsNothing(tWrit er)) Then
tWriter.Close()
End If

If (Not IsNothing(strWr iter)) Then
strWriter.Close ()
End If
End Try
End Sub
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>Captur e Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:dropdownli st id="DropDownLis t1" runat="server">
<asp:listitem>r ed</asp:listitem>
<asp:listitem>b lue</asp:listitem>
<asp:listitem>g reen</asp:listitem>
</asp:dropdownlis t></div>
</form>
</body>

Is that what you are looking for?
Teemu
"Ken Cox - Microsoft MVP" <BA**********@h otmail.com> wrote in message
news:ei******** ********@TK2MSF TNGP10.phx.gbl. ..

I'm trying to find a way to program in ASP.NET 2.0 but capture the HTML
output. I found the following routine in ASP.NET 2.0 Cookbook from
O'Reilly. It doesn't work if I include a server-side dropdownlist control
on the page. The error is RegisterForEven tValidation can only be called
during Render();

Any ideas?

Ken
Microsoft MVP [ASP.NET]
<%@ Page Language="VB" %>

<script runat="server">
Protected Sub Page_Load _
(ByVal sender As Object, _
ByVal e As System.EventArg s) Handles Me.Load
Const OUTPUT_FILENAME As String = "renderedpage.h tml"
Dim renderedOutput As StringBuilder = Nothing
Dim strWriter As IO.StringWriter = Nothing
Dim tWriter As HtmlTextWriter = Nothing
Dim outputStream As IO.FileStream = Nothing
Dim sWriter As IO.StreamWriter = Nothing
Dim filename As String
Dim nextPage As String

Try
'create a HtmlTextWriter to use for rendering the page
renderedOutput = New StringBuilder
strWriter = New IO.StringWriter (renderedOutput )
tWriter = New HtmlTextWriter( strWriter)

'render the page output
Page.RenderCont rol(tWriter)

'save the rendered output to a file
filename = Server.MapPath( ".") & "\" & OUTPUT_FILENAME
outputStream = New IO.FileStream(f ilename, _
IO.FileMode.Cre ate)
sWriter = New IO.StreamWriter (outputStream)
sWriter.Write(r enderedOutput.T oString())
sWriter.Flush()

'redirect to another page
'NOTE: Continuing with the display of this page will result in
the
' page being rendered a second time which will cause an
exception
' to be thrown
nextPage = "DisplayMessage .aspx?" & _
"PageHeader=Inf ormation" & "&" & _
"Message1=H TML Output Saved To " & OUTPUT_FILENAME
Response.Redire ct(nextPage)

Finally
'clean up
If (Not IsNothing(outpu tStream)) Then
outputStream.Cl ose()
End If

If (Not IsNothing(tWrit er)) Then
tWriter.Close()
End If

If (Not IsNothing(strWr iter)) Then
strWriter.Close ()
End If
End Try
End Sub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Captur e Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:dropdownli st id="DropDownLis t1" runat="server">
<asp:listitem>r ed</asp:listitem>
<asp:listitem>b lue</asp:listitem>
<asp:listitem>g reen</asp:listitem>
</asp:dropdownlis t></div>
</form>
</body>
</html>

Feb 12 '06 #2

Ken Cox - Microsoft MVP

Thanks Teemu! That's perfect!

Ken

"Teemu Keiski" <jo****@aspalli ance.com> wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. ..

I responded already on Forums, but here's for reference
**
Hello,

it complained for me about event validation , so when disabling it with
EnableEventVali dation="False" helped. But, if you try it this way e.g
moving the code to overridden Render method

<%@ Page Language="VB" %>

<script runat="server">

Protected Overrides Sub Render(ByVal writer As
System.Web.UI.H tmlTextWriter)
Const OUTPUT_FILENAME As String = "renderedpage.h tml"
Dim renderedOutput As StringBuilder = Nothing
Dim strWriter As IO.StringWriter = Nothing
Dim tWriter As HtmlTextWriter = Nothing
Dim outputStream As IO.FileStream = Nothing
Dim sWriter As IO.StreamWriter = Nothing
Dim filename As String
Dim nextPage As String

Try
'create a HtmlTextWriter to use for rendering the page
renderedOutput = New StringBuilder
strWriter = New IO.StringWriter (renderedOutput )
tWriter = New HtmlTextWriter( strWriter)

MyBase.Render(t Writer)

'save the rendered output to a file
filename = Server.MapPath( ".") & "\" & OUTPUT_FILENAME
outputStream = New IO.FileStream(f ilename, _
IO.FileMode.Cre ate)
sWriter = New IO.StreamWriter (outputStream)
sWriter.Write(r enderedOutput.T oString())
sWriter.Flush()

' redirect to another page
' NOTE: Continuing with the display of this page will result
in the
' page being rendered a second time which will cause an
exception
' to be thrown
nextPage = "DisplayMessage .aspx?" & _
"PageHeader=Inf ormation" & "&" & _
"Message1=H TML Output Saved To " & OUTPUT_FILENAME
'Response.Redir ect(nextPage)
'Response.Write (renderedOutput .ToString())

writer.Write(re nderedOutput.To String())
Finally

'clean up
If (Not IsNothing(outpu tStream)) Then
outputStream.Cl ose()
End If

If (Not IsNothing(tWrit er)) Then
tWriter.Close()
End If

If (Not IsNothing(strWr iter)) Then
strWriter.Close ()
End If
End Try
End Sub
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>Captur e Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:dropdownli st id="DropDownLis t1" runat="server">
<asp:listitem>r ed</asp:listitem>
<asp:listitem>b lue</asp:listitem>
<asp:listitem>g reen</asp:listitem>
</asp:dropdownlis t></div>
</form>
</body>

Is that what you are looking for?
Teemu

Feb 12 '06 #3

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