Please excuse mo for the delayed answer. RadDataForm internally manages binding DataErrors and there is no easy way to make big changes in this mechanism. However, you can try disabling it. Basically it executes this logic on the BindingValidationError event, so that you can subscribe to it on DataFields' level and handle it there. Then you can implement your own custom validation errors like this:
Please, be advised that in case you choose this approach, you should also manage these errors removal from the validation summary. An alternative approach would be to retemplate the validation summary ItemTemplate, adding a converter that will generate the desired label names. As for the last point of your list, it will be great if you can send us a small project that illustrates your approach via a support ticket, so that we could debug it and implement a solution on our side. Please, do not hesitate to ask us for an example project if you have any difficulties while implementing the proposed approach, in case it meets your requirements.
the Telerik team
Explore the entire Telerik portfolio by downloading the Ultimate Collection trial package. Get it now >>