Unfortunately, there is a bug which allows the editors to create any block from the "quick link" in the content area. But the attribute AllowedTypes stops editors from using drag-n-drop, this works for ContentReference and PageReference as well.

Hi Sara, you can allow only one kind of block with:

        [Display(
            Name = "Header",
            Description = "Place here the Header Text Block",
            GroupName = SystemTabNames.Content,
            Order = 1)]
        [Editable(true)]
        [AllowedBlockTypes(new[] { typeof(HeaderOfferTypeBlock) })]
        public virtual ContentArea HeaderTextBlock { get; set; }

Alfredeo, that will unfortunately not stop editors from creating blocks from the "quick link". Your code will only stop editors from drag-n-dropping blocks to the content area.

However, EPiServer is working on a solution where the "quick link" will work as well.

Before the arrival of the AvailableTypesAttribute I had an ValidationAttribute class with the same name. I've since changed it name but still use it to restrict the types allowed in content areas.

http://world.episerver.com/code/dannymurphy/contentarea-item-restrictions/

regards,

Danny