iHTMLElementrender.drawtodc causes error in VB.net application

[ddd]

Hi,

I am having problems with using the DrawToDC of the
MSHTML.iHTMLElementRender in a VB.net application. For some reason I am
getting a "catastrophic error". I am basing the code on c# examples, and I
am not sure what exactly I am doing wrong. From the C# posts it seems that
the drawtodc has a bug and you need to redifine it, so i followed their
advice and specified an interface as below:
Imports System
Imports System.Drawing
Imports System.Runtime.InteropServices
Imports mshtml

<ComVisible(True), ComImport(),
Guid("3050f669-98b5-11cf-bb82-00aa00bdce0b"), _
InterfaceTypeAttribute(ComInterfaceType.InterfaceI sIUnknown)> _
Interface IHTMLElementRender
Sub DrawToDC(<[In]()> ByVal hDC As IntPtr)
Sub SetDocumentPrinter(<[In](), MarshalAs(UnmanagedType.BStr)> ByVal
bstrPrinterName As String, <[In]()> ByVal hDC As IntPtr)
End Interface 'IHTMLElementRender

On the main form of the application I am doing the following:

Dim objMSHTML As HTMLDocument
Dim objDocument As IHTMLDocument2
Dim ips As IPersistStreamInit

objMSHTML = New HTMLDocument()

ips = DirectCast(objMSHTML, IPersistStreamInit)
ips.InitNew()

objDocument =
objMSHTML.createDocumentFromUrl("http://www.google.com", String.Empty)

Do Until objDocument.readyState = "complete"
Application.DoEvents()
Loop

MsgBox(objDocument.body.outerHTML)
Dim bodyElement As IHTMLElement
Dim render As IHTMLElementRender
If objDocument.body.outerHTML <> Nothing Then
bodyElement = objDocument.body
render = bodyElement
Dim img As New Bitmap(600, 400)
Dim g As Graphics = Graphics.FromImage(img)
Dim memDC As IntPtr
memDC = g.GetHdc()

Try
render.DrawToDC(memDC)
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End If

It seems like I am getting the HTML document just fine, is just that when I
try to use DrawToDC to get the application to print/send to the DC i Created
in memory, it causes the error.Any ideas on what I am doing wrong?

Here are the links to where I got the C# examples:
http://groups.google.com/groups?hl=e...C%2B%2Bfailure
http://blogs.msdn.com/rfarber/archiv...12/240943.aspx

thanks

[Charles Law]

Are you sure the error occurs on DrawToDc? I would expect an invalid cast
error on the line

render = bodyElement
I also assume that you have Option Strict Off. Turning it on will ensure you
cast objects correctly.

It looks to me like you are caught between two stools. On the one hand you
want a light-weight program without the rendering part of the WebBrowser or
InternetExplorer controls (ShdocVw), and on the other you want to render
elements using the IHTMLElementRender interface.

Unfortunately you can't use this interface unless you host mshtml properly,
and that includes the rendering part.

When you load the document below it is not rendered; just loaded into
memory. Therefore you cannot render it to a device context because there is
no rendered page to copy.

You can continue to manipulate the html as you have below, but if you want
to render it you must either use the WebBrowser/InternetExplorer controls or
host mshtml fully yourself.

HTH

Charles
"ddd" <so******@nowhereforspam.com> wrote in message
news:uO**************@TK2MSFTNGP14.phx.gbl... Hi,

I am having problems with using the DrawToDC of the
MSHTML.iHTMLElementRender in a VB.net application. For some reason I am
getting a "catastrophic error". I am basing the code on c# examples, and I
am not sure what exactly I am doing wrong. From the C# posts it seems that
the drawtodc has a bug and you need to redifine it, so i followed their
advice and specified an interface as below:
Imports System
Imports System.Drawing
Imports System.Runtime.InteropServices
Imports mshtml

<ComVisible(True), ComImport(),
Guid("3050f669-98b5-11cf-bb82-00aa00bdce0b"), _
InterfaceTypeAttribute(ComInterfaceType.InterfaceI sIUnknown)> _
Interface IHTMLElementRender
Sub DrawToDC(<[In]()> ByVal hDC As IntPtr)
Sub SetDocumentPrinter(<[In](), MarshalAs(UnmanagedType.BStr)> ByVal
bstrPrinterName As String, <[In]()> ByVal hDC As IntPtr)
End Interface 'IHTMLElementRender

On the main form of the application I am doing the following:

Dim objMSHTML As HTMLDocument
Dim objDocument As IHTMLDocument2
Dim ips As IPersistStreamInit

objMSHTML = New HTMLDocument()

ips = DirectCast(objMSHTML, IPersistStreamInit)
ips.InitNew()

objDocument =
objMSHTML.createDocumentFromUrl("http://www.google.com", String.Empty)

Do Until objDocument.readyState = "complete"
Application.DoEvents()
Loop

MsgBox(objDocument.body.outerHTML)
Dim bodyElement As IHTMLElement
Dim render As IHTMLElementRender
If objDocument.body.outerHTML <> Nothing Then
bodyElement = objDocument.body
render = bodyElement
Dim img As New Bitmap(600, 400)
Dim g As Graphics = Graphics.FromImage(img)
Dim memDC As IntPtr
memDC = g.GetHdc()

Try
render.DrawToDC(memDC)
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End If

It seems like I am getting the HTML document just fine, is just that when
I
try to use DrawToDC to get the application to print/send to the DC i
Created
in memory, it causes the error.Any ideas on what I am doing wrong?

Here are the links to where I got the C# examples:
http://groups.google.com/groups?hl=e...C%2B%2Bfailure
http://blogs.msdn.com/rfarber/archiv...12/240943.aspx

thanks

[ddd]

Hi Charles,

First of all thanks for taking the time to reply to this post. I am
definetly not getting an error on the render=bodyelement and i do have
Option Explicit On and Option Strict On for the IHTMLElementRender
interface class.

As about using the WebBrowser control. I am not sure how exactly to do this.
I added a reference to SHDocVw, but I still cannot figure out how to do this
properly. Do I just add the references, to I load the page through the
webbrowser object? I did look at the C# example and they declare an object
that as IHTMLDocument2 and than they set it to be the document of the
webbrowser, however, I got errors when I did this. I also was unclear if i
would need to load the URL through Navigate2 (of the webbrowser) or the
createDocumentFromUrl.

Can you point me to any documents/tutorial where they explain how to host
the MSHTML correctly?

thanks

tony

"Charles Law" <bl***@nowhere.com> wrote in message
news:%2****************@TK2MSFTNGP10.phx.gbl...

Are you sure the error occurs on DrawToDc? I would expect an invalid cast
error on the line

render = bodyElement
I also assume that you have Option Strict Off. Turning it on will ensure

you cast objects correctly.

It looks to me like you are caught between two stools. On the one hand you
want a light-weight program without the rendering part of the WebBrowser or InternetExplorer controls (ShdocVw), and on the other you want to render
elements using the IHTMLElementRender interface.

Unfortunately you can't use this interface unless you host mshtml properly, and that includes the rendering part.

When you load the document below it is not rendered; just loaded into
memory. Therefore you cannot render it to a device context because there is no rendered page to copy.

You can continue to manipulate the html as you have below, but if you want
to render it you must either use the WebBrowser/InternetExplorer controls or host mshtml fully yourself.

HTH

Charles
"ddd" <so******@nowhereforspam.com> wrote in message
news:uO**************@TK2MSFTNGP14.phx.gbl...

Hi,

I am having problems with using the DrawToDC of the
MSHTML.iHTMLElementRender in a VB.net application. For some reason I am
getting a "catastrophic error". I am basing the code on c# examples, and I am not sure what exactly I am doing wrong. From the C# posts it seems that the drawtodc has a bug and you need to redifine it, so i followed their
advice and specified an interface as below:
Imports System
Imports System.Drawing
Imports System.Runtime.InteropServices
Imports mshtml

<ComVisible(True), ComImport(),
Guid("3050f669-98b5-11cf-bb82-00aa00bdce0b"), _
InterfaceTypeAttribute(ComInterfaceType.InterfaceI sIUnknown)> _
Interface IHTMLElementRender
Sub DrawToDC(<[In]()> ByVal hDC As IntPtr)
Sub SetDocumentPrinter(<[In](), MarshalAs(UnmanagedType.BStr)> ByVal
bstrPrinterName As String, <[In]()> ByVal hDC As IntPtr)
End Interface 'IHTMLElementRender

On the main form of the application I am doing the following:

Dim objMSHTML As HTMLDocument
Dim objDocument As IHTMLDocument2
Dim ips As IPersistStreamInit

objMSHTML = New HTMLDocument()

ips = DirectCast(objMSHTML, IPersistStreamInit)
ips.InitNew()

objDocument =
objMSHTML.createDocumentFromUrl("http://www.google.com", String.Empty)

Do Until objDocument.readyState = "complete"
Application.DoEvents()
Loop

MsgBox(objDocument.body.outerHTML)
Dim bodyElement As IHTMLElement
Dim render As IHTMLElementRender
If objDocument.body.outerHTML <> Nothing Then
bodyElement = objDocument.body
render = bodyElement
Dim img As New Bitmap(600, 400)
Dim g As Graphics = Graphics.FromImage(img)
Dim memDC As IntPtr
memDC = g.GetHdc()

Try
render.DrawToDC(memDC)
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End If

It seems like I am getting the HTML document just fine, is just that when I
try to use DrawToDC to get the application to print/send to the DC i
Created
in memory, it causes the error.Any ideas on what I am doing wrong?

Here are the links to where I got the C# examples:
http://groups.google.com/groups?hl=e...C%2B%2Bfailure http://blogs.msdn.com/rfarber/archiv...12/240943.aspx

thanks

[ddd]

I tried the following code which use the internetexplorer to load the page
and than use MSHTML, but this time I got a cast error at the
render=Bodyelement, didn't even make it to the DrawToDc.

Dim browser As New SHDocVw.InternetExplorer()

browser.Navigate("http://www.google.com")

Do Until browser.ReadyState = 4
Application.DoEvents()
Loop
Dim objDocument As IHTMLDocument2 = browser.Document

MsgBox(objDocument.body.outerHTML)

Dim bodyElement As IHTMLElement = objDocument.body

Dim render As IHTMLElementRender = bodyElement
Dim img As New Bitmap(600, 400)
Dim g As Graphics = Graphics.FromImage(img)
Dim memDC As IntPtr
memDC = g.GetHdc()

Try
render.DrawToDC(memDC)
Catch ex As Exception
MsgBox(ex.ToString)
End Try

I also tried to use the webbrowser and iWebBrowser2 like in the c# examples
but no luck in getting them work either. for some reason Navigate/Navigate2
were throwing uknown errors (i think because the control was not in the
form).

Any suggestions?
thanks

tony
"Charles Law" <bl***@nowhere.com> wrote in message
news:%2****************@TK2MSFTNGP10.phx.gbl...

Are you sure the error occurs on DrawToDc? I would expect an invalid cast
error on the line

render = bodyElement
I also assume that you have Option Strict Off. Turning it on will ensure

you cast objects correctly.

It looks to me like you are caught between two stools. On the one hand you
want a light-weight program without the rendering part of the WebBrowser or InternetExplorer controls (ShdocVw), and on the other you want to render
elements using the IHTMLElementRender interface.

Unfortunately you can't use this interface unless you host mshtml properly, and that includes the rendering part.

When you load the document below it is not rendered; just loaded into
memory. Therefore you cannot render it to a device context because there is no rendered page to copy.

You can continue to manipulate the html as you have below, but if you want
to render it you must either use the WebBrowser/InternetExplorer controls or host mshtml fully yourself.

HTH

Charles
"ddd" <so******@nowhereforspam.com> wrote in message
news:uO**************@TK2MSFTNGP14.phx.gbl...

Hi,

I am having problems with using the DrawToDC of the
MSHTML.iHTMLElementRender in a VB.net application. For some reason I am
getting a "catastrophic error". I am basing the code on c# examples, and I am not sure what exactly I am doing wrong. From the C# posts it seems that the drawtodc has a bug and you need to redifine it, so i followed their
advice and specified an interface as below:
Imports System
Imports System.Drawing
Imports System.Runtime.InteropServices
Imports mshtml

<ComVisible(True), ComImport(),
Guid("3050f669-98b5-11cf-bb82-00aa00bdce0b"), _
InterfaceTypeAttribute(ComInterfaceType.InterfaceI sIUnknown)> _
Interface IHTMLElementRender
Sub DrawToDC(<[In]()> ByVal hDC As IntPtr)
Sub SetDocumentPrinter(<[In](), MarshalAs(UnmanagedType.BStr)> ByVal
bstrPrinterName As String, <[In]()> ByVal hDC As IntPtr)
End Interface 'IHTMLElementRender

On the main form of the application I am doing the following:

Dim objMSHTML As HTMLDocument
Dim objDocument As IHTMLDocument2
Dim ips As IPersistStreamInit

objMSHTML = New HTMLDocument()

ips = DirectCast(objMSHTML, IPersistStreamInit)
ips.InitNew()

objDocument =
objMSHTML.createDocumentFromUrl("http://www.google.com", String.Empty)

Do Until objDocument.readyState = "complete"
Application.DoEvents()
Loop

MsgBox(objDocument.body.outerHTML)
Dim bodyElement As IHTMLElement
Dim render As IHTMLElementRender
If objDocument.body.outerHTML <> Nothing Then
bodyElement = objDocument.body
render = bodyElement
Dim img As New Bitmap(600, 400)
Dim g As Graphics = Graphics.FromImage(img)
Dim memDC As IntPtr
memDC = g.GetHdc()

Try
render.DrawToDC(memDC)
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End If

It seems like I am getting the HTML document just fine, is just that when I
try to use DrawToDC to get the application to print/send to the DC i
Created
in memory, it causes the error.Any ideas on what I am doing wrong?

Here are the links to where I got the C# examples:
http://groups.google.com/groups?hl=e...C%2B%2Bfailure http://blogs.msdn.com/rfarber/archiv...12/240943.aspx

thanks

[Charles Law]

The easiest way in VB.NET is still to add a WebBrowser control to a form.
When I select Customize Toolbox, it shows up on the COM Components tab as
Microsoft Web Browser.

When you do this the WebBrowser control will be wrapped (it is an ActiveX)
and called AxWebBrowser1, indicating that it is wrapped in an AxHost. This
is to marshal calls backwards and forwards between managed and unmanaged
code.

The AxWebBrowser1 object will have a document property, which supports the
IHTMLDocument2 interface, amongst others.

If you do this you should find that you can cast bodyElement to render, as
in

render = DirectCast(bodyElement, mshtml.IHTMLElementRender)

Just a note on the Option Strict thing: when you say that you have it on, do
you mean that you have a statement

Option Strict On

at the start of the module containing the code? If so, I would expect a
compile error on the line

render = bodyElement

because they are not the same types.

HTH

Charles
"ddd" <so******@nowhereforspam.com> wrote in message
news:%2******************@TK2MSFTNGP11.phx.gbl...

Hi Charles,

First of all thanks for taking the time to reply to this post. I am
definetly not getting an error on the render=bodyelement and i do have
Option Explicit On and Option Strict On for the IHTMLElementRender
interface class.

As about using the WebBrowser control. I am not sure how exactly to do
this.
I added a reference to SHDocVw, but I still cannot figure out how to do
this
properly. Do I just add the references, to I load the page through the
webbrowser object? I did look at the C# example and they declare an object
that as IHTMLDocument2 and than they set it to be the document of the
webbrowser, however, I got errors when I did this. I also was unclear if i
would need to load the URL through Navigate2 (of the webbrowser) or the
createDocumentFromUrl.

Can you point me to any documents/tutorial where they explain how to host
the MSHTML correctly?

thanks

tony

"Charles Law" <bl***@nowhere.com> wrote in message
news:%2****************@TK2MSFTNGP10.phx.gbl...

Are you sure the error occurs on DrawToDc? I would expect an invalid cast
error on the line

> render = bodyElement

I also assume that you have Option Strict Off. Turning it on will ensure

you

cast objects correctly.

It looks to me like you are caught between two stools. On the one hand
you
want a light-weight program without the rendering part of the WebBrowser

or

InternetExplorer controls (ShdocVw), and on the other you want to render
elements using the IHTMLElementRender interface.

Unfortunately you can't use this interface unless you host mshtml

properly,

and that includes the rendering part.

When you load the document below it is not rendered; just loaded into
memory. Therefore you cannot render it to a device context because there

is

no rendered page to copy.

You can continue to manipulate the html as you have below, but if you
want
to render it you must either use the WebBrowser/InternetExplorer controls

or

host mshtml fully yourself.

HTH

Charles
"ddd" <so******@nowhereforspam.com> wrote in message
news:uO**************@TK2MSFTNGP14.phx.gbl...

> Hi,
>
> I am having problems with using the DrawToDC of the
> MSHTML.iHTMLElementRender in a VB.net application. For some reason I am
> getting a "catastrophic error". I am basing the code on c# examples,
> and I > am not sure what exactly I am doing wrong. From the C# posts it seems that > the drawtodc has a bug and you need to redifine it, so i followed their
> advice and specified an interface as below:
>
>
> Imports System
> Imports System.Drawing
> Imports System.Runtime.InteropServices
> Imports mshtml
>
> <ComVisible(True), ComImport(),
> Guid("3050f669-98b5-11cf-bb82-00aa00bdce0b"), _
> InterfaceTypeAttribute(ComInterfaceType.InterfaceI sIUnknown)> _
> Interface IHTMLElementRender
> Sub DrawToDC(<[In]()> ByVal hDC As IntPtr)
> Sub SetDocumentPrinter(<[In](), MarshalAs(UnmanagedType.BStr)> ByVal
> bstrPrinterName As String, <[In]()> ByVal hDC As IntPtr)
> End Interface 'IHTMLElementRender
>
> On the main form of the application I am doing the following:
>
> Dim objMSHTML As HTMLDocument
> Dim objDocument As IHTMLDocument2
> Dim ips As IPersistStreamInit
>
> objMSHTML = New HTMLDocument()
>
> ips = DirectCast(objMSHTML, IPersistStreamInit)
> ips.InitNew()
>
> objDocument =
> objMSHTML.createDocumentFromUrl("http://www.google.com", String.Empty)
>
> Do Until objDocument.readyState = "complete"
> Application.DoEvents()
> Loop
>
> MsgBox(objDocument.body.outerHTML)
> Dim bodyElement As IHTMLElement
> Dim render As IHTMLElementRender
>
>
> If objDocument.body.outerHTML <> Nothing Then
> bodyElement = objDocument.body
> render = bodyElement
> Dim img As New Bitmap(600, 400)
> Dim g As Graphics = Graphics.FromImage(img)
> Dim memDC As IntPtr
> memDC = g.GetHdc()
>
> Try
> render.DrawToDC(memDC)
> Catch ex As Exception
> MsgBox(ex.ToString)
> End Try
>
>
> End If
>
> It seems like I am getting the HTML document just fine, is just that when > I
> try to use DrawToDC to get the application to print/send to the DC i
> Created
> in memory, it causes the error.Any ideas on what I am doing wrong?
>
> Here are the links to where I got the C# examples:
> http://groups.google.com/groups?hl=e...C%2B%2Bfailure > http://blogs.msdn.com/rfarber/archiv...12/240943.aspx
>
> thanks
>
>

[Charles Law]

You are right about the unknown errors (unspecified error, I think). This
is, as you surmise, because mshtml is not hosted properly. As per my other
reply, the easiest way to is to put a WebBrowser control on the form. I
wouldn't recommend going the other route (hosting it manually) as all you
will end up doing is recreating the code already in the WebBrowser control,
and it is not for the faint-hearted.

Charles
"ddd" <so******@nowhereforspam.com> wrote in message
news:u4**************@TK2MSFTNGP12.phx.gbl...

I tried the following code which use the internetexplorer to load the page
and than use MSHTML, but this time I got a cast error at the
render=Bodyelement, didn't even make it to the DrawToDc.

Dim browser As New SHDocVw.InternetExplorer()

browser.Navigate("http://www.google.com")

Do Until browser.ReadyState = 4
Application.DoEvents()
Loop
Dim objDocument As IHTMLDocument2 = browser.Document

MsgBox(objDocument.body.outerHTML)

Dim bodyElement As IHTMLElement = objDocument.body

Dim render As IHTMLElementRender = bodyElement
Dim img As New Bitmap(600, 400)
Dim g As Graphics = Graphics.FromImage(img)
Dim memDC As IntPtr
memDC = g.GetHdc()

Try
render.DrawToDC(memDC)
Catch ex As Exception
MsgBox(ex.ToString)
End Try

I also tried to use the webbrowser and iWebBrowser2 like in the c#
examples
but no luck in getting them work either. for some reason
Navigate/Navigate2
were throwing uknown errors (i think because the control was not in the
form).

Any suggestions?
thanks

tony
"Charles Law" <bl***@nowhere.com> wrote in message
news:%2****************@TK2MSFTNGP10.phx.gbl...

Are you sure the error occurs on DrawToDc? I would expect an invalid cast
error on the line

> render = bodyElement

I also assume that you have Option Strict Off. Turning it on will ensure

you

cast objects correctly.

It looks to me like you are caught between two stools. On the one hand
you
want a light-weight program without the rendering part of the WebBrowser

or

InternetExplorer controls (ShdocVw), and on the other you want to render
elements using the IHTMLElementRender interface.

Unfortunately you can't use this interface unless you host mshtml

properly,

and that includes the rendering part.

When you load the document below it is not rendered; just loaded into
memory. Therefore you cannot render it to a device context because there

is

no rendered page to copy.

You can continue to manipulate the html as you have below, but if you
want
to render it you must either use the WebBrowser/InternetExplorer controls

or

host mshtml fully yourself.

HTH

Charles
"ddd" <so******@nowhereforspam.com> wrote in message
news:uO**************@TK2MSFTNGP14.phx.gbl...

> Hi,
>
> I am having problems with using the DrawToDC of the
> MSHTML.iHTMLElementRender in a VB.net application. For some reason I am
> getting a "catastrophic error". I am basing the code on c# examples,
> and I > am not sure what exactly I am doing wrong. From the C# posts it seems that > the drawtodc has a bug and you need to redifine it, so i followed their
> advice and specified an interface as below:
>
>
> Imports System
> Imports System.Drawing
> Imports System.Runtime.InteropServices
> Imports mshtml
>
> <ComVisible(True), ComImport(),
> Guid("3050f669-98b5-11cf-bb82-00aa00bdce0b"), _
> InterfaceTypeAttribute(ComInterfaceType.InterfaceI sIUnknown)> _
> Interface IHTMLElementRender
> Sub DrawToDC(<[In]()> ByVal hDC As IntPtr)
> Sub SetDocumentPrinter(<[In](), MarshalAs(UnmanagedType.BStr)> ByVal
> bstrPrinterName As String, <[In]()> ByVal hDC As IntPtr)
> End Interface 'IHTMLElementRender
>
> On the main form of the application I am doing the following:
>
> Dim objMSHTML As HTMLDocument
> Dim objDocument As IHTMLDocument2
> Dim ips As IPersistStreamInit
>
> objMSHTML = New HTMLDocument()
>
> ips = DirectCast(objMSHTML, IPersistStreamInit)
> ips.InitNew()
>
> objDocument =
> objMSHTML.createDocumentFromUrl("http://www.google.com", String.Empty)
>
> Do Until objDocument.readyState = "complete"
> Application.DoEvents()
> Loop
>
> MsgBox(objDocument.body.outerHTML)
> Dim bodyElement As IHTMLElement
> Dim render As IHTMLElementRender
>
>
> If objDocument.body.outerHTML <> Nothing Then
> bodyElement = objDocument.body
> render = bodyElement
> Dim img As New Bitmap(600, 400)
> Dim g As Graphics = Graphics.FromImage(img)
> Dim memDC As IntPtr
> memDC = g.GetHdc()
>
> Try
> render.DrawToDC(memDC)
> Catch ex As Exception
> MsgBox(ex.ToString)
> End Try
>
>
> End If
>
> It seems like I am getting the HTML document just fine, is just that when > I
> try to use DrawToDC to get the application to print/send to the DC i
> Created
> in memory, it causes the error.Any ideas on what I am doing wrong?
>
> Here are the links to where I got the C# examples:
> http://groups.google.com/groups?hl=e...C%2B%2Bfailure > http://blogs.msdn.com/rfarber/archiv...12/240943.aspx
>
> thanks
>
>