Sharepoint multi-column validation

Question

I've got a custom list that contains multi collumns. The validation is made by a custom contenttype. Now I want a combination of two columns to be unique. Until know I did not found a way to solve this problem with on-board functions, so my idea was to use the eventreceiver or a customcontenttype.

What I tried:

ListEventReceiver

public override void ItemAdding(SPItemEventProperties properties)
       {

           if (properties.AfterProperties["a1"].ToString() == properties.AfterProperties["a2"].ToString())
           {
               properties.Status = SPEventReceiverStatus.CancelWithError;
               properties.Cancel = true;
               properties.ErrorMessage = "Failure";
           }
           base.ItemAdding(properties);
       }

It works fine, but the error message is not show as a validation error. It is a new errorpage.

CustomContenttype

If I try to validate in a custom contenttype I can not access the value of an other field from the contenttype. So I can not compare two fields or check they are unique.

Answer 1

I think the only answer would be to look at doing this in Javascript on the client side.

I would also like to find a way to do this in server code and have it return a validation indication of an error, something like a "*" instead of a huge error page that cancels the entire entry.

Let me know if you have found your answer!

Answer 2

Could this be achieved by using a formula within the list validation settings?

Got to your List and select List Settings > Validation Settings. Use the below formula:

=[a1]<>[a2]

There is also an area for entering a user message for the validation error.