April 12, 2019

Limit TreelistEx Selections to X Number of Items

April 12, 2019

Sitecore Item Limit

I recently had a requirement to limit the content author's ability to select items.  In this case, they were only allowed to select two items.  I love using "TreeListEx" and therefore selected that field type.  I knew that I could set validation on fields and went about looking for the built-in validator that would limit the number of selections. . . I didn't find it.

While I was surprised to not find this validator, I thought that surely, someone else smarter than me had mentioned it on the interwebs; I was not disappointed.  A quick search yielded a StackOverflow post about it that cited a blog post.  In summary, apply a Regex value to the "Validation" field of your field. (Add a helpful "ValidationText" message while you're at it.)

I dutifully copied and pasted the Regex expression into my field and was a little surprised to see an error message while testing the validator:

Sitecore Validation Error

Well, that didn't go as expected.  After a bit of Internet sleuthing on the error, I found that there might be a character (or "characters") in the string that needs to be escaped.  I simply changed "^({[^}]+}|?){0,2}$" to "^(\{[^}]+\}|\?){0,2}$" (included the escaping 'backslashes' before the curly brackets and question mark) and was on my way!

Sitecore Validation Working

Update: And of course as I'm finalizing the research for this post, I see that Ben *actually* did solve this and it can be seen in the screenshot he included, but the Regex text in his post didn't include the escape characters


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