question

Hi @AmitRawat-3636,

In sharepoint on OnPremise CSOM, there is no exist api to get the versions of the items. That's why you get the error. If you want to get version history of a list item, you may need to use SharePoint web service to retrieve the version history and related data of list item In client-side. You could refer to this post: https://social.msdn.microsoft.com/Forums/SqlServer/en-US/177ceafb-debd-4020-b943-904c220cbf5f/how-to-get-list-item-versions-using-csom?forum=appsforsharepoint

And we could get the content for a wiki page like this:

         ListItem item = web.Lists.GetByTitle("Site Pages").GetItemById(11);
         ctx.Load(item);
         ctx.ExecuteQuery();            
         Console.WriteLine(item["WikiField"]);

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