MSXML COM Object

  • Thread starter Thread starter rajkiranpro
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rajkiranpro

I tried to create an object of xmlhttpclass.

MSXML2.XMLHTTPClass xmlclass = new MSXML2.XMLHTTPClass();
xmlclass.open("POST", txtURL.Text, false, null, null);
xmlclass.setRequestHeader("Content-Type",
"application/x-www-form-urlencoded");
xmlclass.send(txtRequest.Text);
System.IO.StreamReader sr = new
System.IO.StreamReader((System.IO.Stream)xmlclass.responseStream);
txtREsponse.Text = sr.ReadToEnd();
sr.Close();

however I couldn't get the response stream. I get the following error while
doing so

Unable to cast COM object of type 'System.__ComObject' to class type
'System.IO.Stream'. Instances of types that represent COM components cannot
be cast to types that do not represent COM components; however they can be
cast to interfaces as long as the underlying COM component supports
QueryInterface calls for the IID of the interface.

Please help me


Regards
Rajkiran
 
rajkiranpro said:
I tried to create an object of xmlhttpclass.
Click to expand...
Why? .NET has perfectly serviceable classes for this. If you are not just
copying old VB/ASP code and trying to port it, I'm very interested in the
kind of scenario that would need this.
MSXML2.XMLHTTPClass xmlclass = new MSXML2.XMLHTTPClass();
xmlclass.open("POST", txtURL.Text, false, null, null);
xmlclass.setRequestHeader("Content-Type",
"application/x-www-form-urlencoded");
xmlclass.send(txtRequest.Text);
System.IO.StreamReader sr = new
System.IO.StreamReader((System.IO.Stream)xmlclass.responseStream);
txtREsponse.Text = sr.ReadToEnd();
sr.Close();
Click to expand...
The .NET equivalent is

WebClient webClient = new WebClient();
webClient.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
txtResponse.Text = webClient.UploadString(txtURL.Text, txtRequest.Text);

Much simpler, no?

If you are going to .NET from the unmanaged world, I recommend reading a
book on getting started with .NET first, to get an idea of what the
framework supports. Trying to force in unmanaged concepts is a recipe for
disaster.
Unable to cast COM object of type 'System.__ComObject' to class type
'System.IO.Stream'. Instances of types that represent COM components
cannot be cast to types that do not represent COM components; however
they can be cast to interfaces as long as the underlying COM component
supports QueryInterface calls for the IID of the interface.
Click to expand...
First of all, the XMLHTTP object has a "responseText" property that allows
you to read the response directly as a string, so no need to muck about with
streams even if you do want to use XMLHTTP for some reason I can't fathom.

Second, if you absolutely do need to get the stream of XMLHTTP, try
Marshal.GetObjectForNativeVariant(xmlclass.responseStream). This *should*
return a Stream instance, but I haven't tested it (I'm not sure it supports
IStream variants).
 
thanks for the answer.

yes I implemented first using the webclient and it worked perfect.

I just wanted to try the same using MSXML com object.

and I`ll try using the Marshal
 
rajkiranpro said:
thanks for the answer.

yes I implemented first using the webclient and it worked perfect.

I just wanted to try the same using MSXML com object.

and I`ll try using the Marshal
Click to expand...

Could you elaborate why you would using MSXML (which in this case is acting
merely as a way to use the WinINet) stack, when the .NET Fx has much better
API for this sort of thing?
 
just tried how to use com components under .net


Anthony Jones said:
Could you elaborate why you would using MSXML (which in this case is
acting merely as a way to use the WinINet) stack, when the .NET Fx has
much better API for this sort of thing?
Click to expand...
 
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