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POPublic member 'elements' on type 'DBNull' not found
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copied!<p>We have an ActiveX component that displays a Web page in an Internet Explorer window via SHDocVw. In the DocumentComplete event handler, we attempt to retrieve the value from one of the controls on the page. We <em>know</em> the control is on the page (it's visible via a <a href="http://fiddler2.com/" rel="nofollow">Fiddler</a> trace).</p> <p>It's at this point that things get wonky. We receive the following error message at runtime:</p> <pre><code>Error Message: Public member 'elements' on type 'DBNull' not found. Error Routine Location: at Microsoft.VisualBasic.CompilerServices.Symbols.Container.GetMembers(String& MemberName, Boolean ReportErrors) at Microsoft.VisualBasic.CompilerServices.NewLateBinding.LateGet(Object Instance, Type Type, String MemberName, Object[] Arguments, String[] ArgumentNames, Type[] TypeArguments, Boolean[] CopyBack) at Foo.AddinModule.m_internetExplorer_DownloadComplete(Object pDisp, Object& url) Error Source: Microsoft.VisualBasic Error Site Location: System.Reflection.MemberInfo[] GetMembers(System.String ByRef, Boolean) </code></pre> <p>The offending line of code is this one:</p> <pre><code>Me.IEInstance.Document.forms("frmRedirect").elements("redirectData").Value = outlookXML.OuterXml </code></pre> <p>So, essentially, <code>Me.IEInstance.Document.forms("frmRedirect")</code> is evaluating to <code>DBNull</code>.</p> <p>We've eliminated case sensitivity issues. Tried moving the control around within the page, and verified that the HTML is well-formed. I have no idea why this is occurring. A sample of the generated HTML is below.</p> <p>Can anyone suggest a cause and a possible resolution for this issue? I'm entertaining any and all suggestions at this point.</p> <p><strong>HTML Sample</strong></p> <pre><code><form id='frmRedirect' name='frmRedirect' action='pw_outlook/choosecontacts.aspx' method='POST'> <input type='hidden' name='redirectData'> </form> </code></pre> <p><strong>UPDATE 3/28/2012</strong></p> <p>We have determined that the code works fine under certain configurations. Then, mysteriously, it will succeed <em>for some users</em> if you change the code as follows:</p> <pre><code>Me.IEInstance.Document.forms("frmRedirect").Elements("redirectData").Value = outlookXML.OuterXml ^ ^ </code></pre> <p>That is, if you simply change the case of <code>Elements</code>. This, to me, smacks of a case sensitivity issue during a COM vtable lookup, but the mystery is that it doesn't occur for everyone. Just <em>some</em> users.</p> <p>Also, please note that the form that is returned by <code>.forms("frmRedirect")</code> is a valid object; however, it doesn't appear to have an <code>elements()</code> method.</p>

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