Adding new fields to search

we are adding some fileds to the documents  by using 

static void Events_BeforeBulkIndex(BeforeBulkIndexingEventArgs e){
foreach (var doc in e.Documents)
			{
			
			if (doc.ContentTypeId == apiBlogPost.ContentTypeId)
				{
				BlogPost blogPost = apiBlogPost.Get(doc.ContentId);
					if (blogPost == null) return;
					var labelvalue = blogPost.ExtendedAttributes["somefiled"]?.Value;
					if (!string.IsNullOrEmpty(labelvalue))
					{
						doc.AddField("key", labelvalue);
							}
					
				}
			
			}
			
}

But if we search for the value , we are unable to find them in search results