Proxy Items and Reference Items

Proxy items in Sitecore are, loosely speaking, pointers to source content items located elsewhere in the content tree. Editing a proxy item updates the source item and vice-versa. To create a proxy item, consult the documentation provided on the SDN (http://sdn5.sitecore.net/Articles/Administration/Using%20Proxy%20Items%20in%205,-d-,3/What%20is%20a%20Proxy%20Item.aspx). Note that using proxy items may have performance impacts and the documentation should be consulted closely before using this approach. Additionally, requirements should be carefully analyzed and prototyped to ensure that proxy items provide a complete solution.

Developers sometimes envision proxy items as a solution for content sharing:

I. Sitecore
  a. Content
    i. Site A
      1. Content Item A
    ii. Site B
      1. Proxy of Content Item A

While this may initially appear to be an ideal solution, at least one major problem presents itself – proxy items cannot have unique presentation settings. In other words, the proxied content item will use the same presentation settings (i.e. layout, sublayouts and renderings) as are applied to the source content item. In this case, even though the proxied item is in Site B, it will be rendered in the same manner as the source item in Site A. While it may be possible to work around this – for example by implementing a pipeline processor – this approach may become complex quickly, particularly if you deploy many proxy items.

The most common use of proxy items is for lookup values that do not require presentation settings and may, in fact, be located in different databases. Consider, for example, a requirement that business users be able to associate a content item (perhaps a site or a major branch of a site) with particular users or roles. This metadata may be used to drive email notifications within workflow actions. The Security database (containing user and role information for content authors) may be proxied to a global folder in the main content tree. For example:

I. Content
  a. Global
    i. Users
      1. User A
      2. User B
  b. Home
    i. Content Item A

Content Item A may have a multilist field whose source is /sitecore/content/Global/Users.

Another instance of using proxy items is in proxying data sourced from an external data provider. The Sitecore Sharepoint Module uses this approach. Sitecore allows Sharepoint document libraries or lists to appear as proxy items in the Media Library or elsewhere in the content tree.

"Reference items" are a simpler, but in some ways more complete, approach to referencing other content items. A reference item is an item whose template has at least one field that references another content item. Consider the following template design:

Product
Title	Text
Description	Rich Text
Reference Item	Reference

The reference field type provides a tree control that allows users to choose any item in the content tree to which they have read access.

The advantages to using reference items are at least two fold: 1) Presentation settings can be placed on reference items completely independently of the item referenced and 2) Fields in the reference item can – through presentation logic – implicitly override the same fields in the source item. Some disadvantages to using reference items are: 1) Presentation logic becomes more complicated, 2) The concept of referencing other content items may be confusing to business users and 3) Dependencies are created between content items. Presentation logic will be required to handle unforeseen scenarios (such as the deletion of the source item). When using this approach, consider pre-populating the reference fields in template standard values to simplify the configuration for business users.