无法将类型为“System .__ ComObject”的COM对象强制转换为类类型“System.Xml.XmlDocument”

问题描述：

我有一个com组件，我已在我的vb.net项目中注册并添加为参考。在尝试访问其方法时，我收到上述错误。需要你的帮助。

以下是代码片段

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）

这里ComReferenceDLL是COM组件。

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.

答

当然你不能。谁告诉你这些类型是以某种方式相关的，忘了它的赋值兼容性。

你不应该将旧的不太好的COM与.NET FCL类混合使用，已经为您提供阅读，解析和生成XML所需的一切。这是我对它们的简短概述：

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:

使用 System.Xml.XmlDocument 类。它实现了DOM接口;如果文档的大小不是太大，这种方式是最简单和最好的。
参见 http://msdn.microsoft.com/en-us/library/system.xml.xmldocument.aspx [ ^ ]。
使用类 System.Xml.XmlTextReader ;这是最快的阅读方式，特别是你需要跳过一些数据。
参见 http://msdn.microsoft.com/en-us/library/system.xml.xmlreader.aspx [ ^ ]。
使用类 System.Xml.Linq.XDocument ;这是类似于 XmlDocument 的最合适的方式，支持LINQ to XML Programming。
参见 http://msdn.microsoft.com/en-us/library/system.xml.xmldocument.aspx [ ^ ]，http://msdn.microsoft.com/en-us/library/bb387063.aspx [ ^ ]。

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

无法将类型为“System .__ ComObject”的COM对象强制转换为类类型“System.Xml.XmlDocument”

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