XML code no longer working in SharePoint

Question

I have a SharePoint that displays data from the parent site in a sub-site. I used SharePoint Designer to set up the web parts that I needed. (see http://sharepointontop.blogspot.com/2012/06/show-listview-webpart-from-parent-site.html ) These sites use the classic template for SharePoint. The sites worked fine until my organisation migrated to a new O365 tenancy. The parent site was migrated without loss of data and all links on the page worked. However, the sub-site home page was bare. None of the data and the page formatting was migrated.

I thought, no problem. I could recreate the subsite, but I fell at the first hurdle. When I tried to set up the first web part and import the appropriate list (as per the above process), I got an error message:

I looked at the XML file and there were indeed errors in the file, at least as far as the validation tools I used were concerned. What I don't understand is that the XML code should not have changed as the SharePoint data on which the webpart file is based did not change with the migration, apart from the URL for the site. Did the migration change something that I cannot see in the file? I did not save the XML code from before the migration, so have nothing to compare it with.

Can anyone explain what might have gone wrong and if there is a solution to my dilemma? 

Answer 1

Hi @Steve Kennedy ,

I could reproduce this issue, however I am unable to find a workaround for it.

I am a bit regretful that I wasn’t able to help you much on this.

In this case, I would propose a new support ticket to be raised to have a dedicated Technical Professional to support you from there. The contact number for your region could be easily found from below website, you can simply refer to the Customer Service Representative and he/she will be glad to help you with creating a new ticket.

https://support.microsoft.com/en-us/topic/global-customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2

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Answer 2

This is may due to the deprecation and removal of the DataFormWebPart as part of MC242207.

Message Summary
To enhance data integrity and improve the overall reliability of the service, we are retiring support for external XSLT file references for the DataFormWebParts and its sub-classes (e.g. XsltListFormWebPart, XsltListViewWebPart).

This retirement affects only classic SharePoint pages.

Key points

Timing: mid-March
Roll-out: tenant level
Action: review and assess before March 15, 2021
How this affects your organization

Support for external XSLT files references in the DataFormsWebPart and its subclasses will no longer be available after March 14, 2021.

After March 14, 2021, the DataFormsWebPart will be unable to perform functions that rely on external XSLT code.
If you are currently using a DataFormWebPart that references external XSLT code, you will need to modify the reference to an internal XSLT file located in the site’s asset library instead.
Potential scenarios for using the DataFormWebParts on classic SharePoint pages:

DataFormWebParts have been created via SharePoint Designer and include XSLT code
DataFormWebParts have been created and customized in the browser or via PowerShell to include XSLT code
What you need to do to prepare

Conduct an audit of DataFormWebParts for all classic SharePoint pages that may exist in your tenant. If you discover external XSLT references, remove them.

To retain the same functionality as before, use one of two methods:

Copy the external XSLT files to the asset library of the same site on which the DataFormWebParts are hosted. Then reference the XSLT files from there instead.
Consider using a modern solution such as JSLink for classic SharePoint pages, and SPFx or custom formatters for SharePoint modern pages and lists.