Looking up values in Validation Rules

The VLookup function provides the ability to lookup values from other objects.  Note that it ONLY works on Custom Objects.  The format is: VLookup(field_to_return, field_on_lookup_object, lookup_value).

So if you need need to lookup an item from a custom table with an Id of 00Xj000000NK03j, and return the name, the formula would look something like this:  

Viewing the ValidationExceptions Collection

Occassionally, .NET apps that are using EntityFramework will throw the following error

System.Data.Entity.Validation.DbEntityValidationException: Validation failed for one or more entities. See 'EntityValidationErrors' property for more details.

The easiest way to see what these exceptions is to add the following to the Watch window:

((System.Data.Entity.Validation.DbEntityValidationException)$exception).EntityValidationErrors