Validation Rule on a Multi select picklist limiting the total number of characters selected

Question

I have a multi-select picklist with many items, however I want the total number of characters to be less than 60. For example a user can select this: apple car banana pineapple watermelon grapefruit melon, but not: apple car banana pineapple watermelon grapefruit melon strawberry because that would be more than 60 characters.

I'm getting an error (items__c is a multi-select picklist field. Multi-select picklist fields are only supported in certain functions), so how can I make my Validation Rule work?

LEN(items__c) >  60)

Answer 1

I don't think you would be able to count the characters of a multipicklist field in a validation rule or even validation + formula combination.

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You might have to roll your own before trigger that counts the length of the string & adds an error if it exceeds any particular length. You can optionally eliminate the value separator (;).

trigger SObjectTrigger on SObject__c (before insert, before update) {
    for(SObject__c record: Trigger.new){
        if(record.items__c != null && record.items__c.replaceAll(';', '').length() > 60){
            record.addError('Items__c', 'Characters can\'t exceed 60');
        }
    }
}