`Article Publish Date` is a field of type `Datetime`

```
List<Item> articles = GetArticles();

articles = articles.OrderByDescending(x => x.Fields[Constants.Templates.Article.Fields.ArticlePublishDate]).ToList();

```

The above line of code throws an error:

> 
> At least one object must implement IComparable.
> 
> 
> 

How can this be resolved.