Unable to cast COM object of type 'System.__ComObject' to class type 'System.Xml.XmlDocument'

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I have a com component, which i have registered and added as reference in my vb.net project. While trying to access its method I am getting the above error. Need your help.

Below is the code snippet

Dim testResult As Object = Nothing
Dim oxmldom As Object
Dim sXML As String
sXML = ""
testResult = CreateObject("ComReferenceDLL.iInterface1")
oxmldom = CreateObject("MSXML2.DOMDocument")
oxmldom = testResult.SampleMethod(sXML)

Here ComReferenceDLL is the COM component.

Posted 19-May-13 20:25pm

preeti_007

Updated 19-May-13 20:28pm

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Sergey Alexandrovich Kryukov 20-May-13 1:40am

Why? why?!
—SA

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Sergey Alexandrovich Kryukov · Answer 1 · 2013-05-19T20:44:00

Of course you cannot. Who told you these type are related somehow, forget about its assignment compatibility.

You should not mix old-not-so-good COM with .NET FCL classes, which already provide you will all you need to reading, parsing and generating XML. This is my short overview of them:

Use System.Xml.XmlDocument class. It implements DOM interface; this way is the easiest and good enough if the size if the document is not too big.
See http://msdn.microsoft.com/en-us/library/system.xml.xmldocument.aspx[^].
Use the class System.Xml.XmlTextReader; this is the fastest way of reading, especially is you need to skip some data.
See http://msdn.microsoft.com/en-us/library/system.xml.xmlreader.aspx[^].
Use the class System.Xml.Linq.XDocument; this is the most adequate way similar to that of XmlDocument, supporting LINQ to XML Programming.
See http://msdn.microsoft.com/en-us/library/system.xml.xmldocument.aspx[^], http://msdn.microsoft.com/en-us/library/bb387063.aspx[^].

—SA

Unable to cast COM object of type 'System.__ComObject' to class type 'System.Xml.XmlDocument'

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Unable to cast COM object of type 'System.__ComObject' to class type 'System.Xml.XmlDocument'

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