How to update properties of existing documents using a Controller. Context: I have a container page that has hunderts of news documents and each of them has many fields, s.a title, body etc. This documents have also SEO related information s.a metatitle and metadescription. I want to create a controller that checks if this fields are empty and in case to fill them with existing fields such as title and body. Follwoing the code of the controller: There is a HTTP requesto to SEO Controller and private methods. FillEmptyFields that should check and fill empty fields and another helper that creates a string. The problem is on FillEmptyFields that does not set the new values and also save them.

>  public class SEOController : UmbracoAuthorizedApiController  {
>      private readonly IContentService _contentService;
>      private readonly ILogger<SEOController> _logger;
>      private readonly HttpClient _httpClient;
>      private readonly IShortStringHelper _shortStringHelper;
>      private readonly IContentTypeBaseServiceProvider _contentTypeBaseServiceProvider;
>      private readonly IUmbracoContextAccessor _accessor;
>      private int index = 150;
> 
>      public SEOController(
>          IContentService contentService,
>          IShortStringHelper shortStringHelper,
>          IContentTypeBaseServiceProvider contentTypeBaseServiceProvider,
>          IUmbracoContextAccessor accessor,
>          ILogger<SEOController> logger)
>      {
>          _logger = logger;
>          _contentService = contentService;
>          _shortStringHelper = shortStringHelper;
>          _contentTypeBaseServiceProvider = contentTypeBaseServiceProvider;
>          _accessor = accessor;
> 
>          _httpClient = new HttpClient();
>      }
> 
>      // ~/umbraco/backoffice/api/seo/news
>      public void News()
>      {
>          _accessor.TryGetUmbracoContext(out var context);
>          IPublishedContent? root = context?.Content?
>              .GetAtRoot()?.First()?
>              .Children(x => x.ContentType.Alias == "knowledgeEvents")?.First()?
>              .Children(x => x.ContentType.Alias == "newsEvents")?
>              .Where(x => x.Name == "News & Events").First();
> 
>          if (root != null)
>          {
>              FillEmptyFields(root.Children());
>          }
>      }
>     private void FillEmptyFields(IEnumerable<IPublishedContent> childrens)
>     {
> 
>         if (childrens != null)
>         {
>             foreach (var child in childrens)
>             {
>                 var itemContent = _contentService.GetById(child.Id);
>                 var singleNewsEventsTitle = child.HasValue("singleNewsEventsTitle") ?
> child.Value<string>("singleNewsEventsTitle") : child.Name;
>                 var body = CreateMetaDescription(child.Value<string>("singleKnowledgeEventsBody"));
>                 var description = CreateMetaDescription(body);
> 
>                 if (string.IsNullOrEmpty(child.Value<string>("title")))
>                 {
>                     itemContent.SetValue("title", singleNewsEventsTitle);
>                 }
> 
>                 if (string.IsNullOrEmpty(child.Value<string>("metaDescription")))
>                 {
>                     itemContent.SetValue("metaDescription", description);
>                 }
>                 if (itemContent != null) _contentService.SaveAndPublish(itemContent);
>             }
>         }
>     }
> 
>     private string CreateMetaDescription(string? body)
>     {
>         string? result = string.Empty;
> 
>         result = (body != null && body.Length >= index) ? string.Concat(body.Substring(index), "...") : body;
> 
>         if (result != null)
>         {
>             return result;
>         }
>         else
>         {
>             return string.Empty;
>         }
>     } }

Here is the error i see:

{"ExceptionMessage":"Variation \"<null>,<null>\" is not supported by the property type.","ExceptionType":null,"StackTrace":null}

Any suggestions?!

Thank You