Cannot add Table Of Contents web part using the Client Object Model

Question

I am trying to add a Table-of-contents webpart to an Enterprise Wiki page using the Client Object Model in a custom migration Add-in for Sharepoint Online.

I have exported the xml for the webpart and it starts with this:

<webParts>
  <webPart xmlns="http://schemas.microsoft.com/WebPart/v3">
    <metaData>
      <type name="Microsoft.SharePoint.Publishing.WebControls.TableOfContentsWebPart, Microsoft.SharePoint.Publishing, Version=16.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" />

I try to add it with the following code:

 Microsoft.SharePoint.Client.File page = context.Web.GetFileByServerRelativeUrl(pageUrl); 
 LimitedWebPartManager lwp = page.GetLimitedWebPartManager(PersonalizationScope.Shared);

 WebPartDefinition wpd = lwp.ImportWebPart(tocWebPartXml);

 lwp.AddWebPart(wpd.WebPart, "wpz", 0); 
 context.ExecuteQueryRetry();

Where pageUrl = "/sites/DKWikiTst/wiki/User_lpedersen/Pages/home.aspx" and the site Url for context is "https://COMPANY.sharepoint.com/sites/DKWikiTst"

But I get "Exception has been thrown by the target of an invocation".

I also tried to add a Document Library web part using this xml:

<?xml version="1.0" encoding="utf-8" ?>
<webParts>
  <webPart xmlns="http://schemas.microsoft.com/WebPart/v3">
    <metaData>
      <type name="Microsoft.SharePoint.WebPartPages.XsltListViewWebPart, Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" />
      <importErrorMessage>Cannot import this Web Part.</importErrorMessage>
    </metaData>
    <data>
      <properties>
        <property name="ListUrl" type="string">MyLibrary</property>
        <property name="MissingAssembly" type="string">Cannot import this Web Part.</property>
      </properties>
    </data>
  </webPart>
</webParts>

That failed with "File not found", but that was because its ListUrl property was set to a placeholder value like "MyLibrary". I changed it to "Documents" and the error went away.

Answer 1

Since Sharepoint errors are meaningless, I had to use trial and error to find the problem. It turns out that 2 properties in the exported XML caused the error. The offending properties were "ListId" and "ListName". After I deleted those two from the XML, the webpart could be added.