Question

I have a LINQ partial class:

public partial class resp {     public IEnumerable<RuleViolation> GetRuleViolations()     {         if (String.IsNullOrEmpty(respName))             yield return new RuleViolation('Responsibility name required', 'respName');         yield break;     }      public bool IsValid     {         // Quick method for checking to see whether an object contains any RuleViolations         get { return (GetRuleViolations().Count() == 0); }     }      partial void OnValidate(ChangeAction action)     {         // Hook to LINQ to be notified before db is actually persisted .. and check to make sure resp is not used by respApprover or approvals         if (action == ChangeAction.Delete && ((respApprovers.Count() != 0 || approvals.Count() != 0)))             throw new ApplicationException('You cannot delete a responsibility that is in use');         if (!IsValid)             throw new ApplicationException('Rule violations prevent saving');     } } 

In my code I would like to be able to check whether a responsibility (dbo.resp) exists before it is deleted.

I am accomplishing this check with a hook to OnValidate as above ... if (action == ChangeAction.Delete) ... and returning an application exception if it fails.

Also, during normal validation, I would like to check to make sure rule violations aren’t made (resp.respName in this case…)

So, normally I can just do a try { } catch { var errors = resps.GetRuleViolations() } and check whether I have validation errors. Of course, that doesn’t know what action is being taken (Changeaction.Delete)

I guess my main question is, how can I have OnValidate return a reason rather than crash my whole app when the Changeaction is delete. Normally I would catch GetRuleViolations but if I put the ‘if statement’ in the GetRuleViolations … it will always be true even during checks to see if the data was correct (in other words, respApprovers.Count() will matter even for checks on new insertions which I don’t want to. I only want those count checks to be made on deletion)

Or possibly more simply stated: I want GetRuleViolations to tell me when someone attempts to delete resp that has respApprovers.Count() > 0 or approvals.Count() > 0 but only when the OnValidate Changeaction is delete.

Answer 1

Change GetRuleViolations to accept the ChangeAction parameter and add a parameterless version that calls it with ChangeAction.None (or Update or Insert, as appropriate). Then move your check in there as you want.

public IEnumerable<RuleViolation> GetRuleViolations( ChangeAction action ) {     if (action == ChangeAction.Delete) {        ...     }     else {        ...     } }  public IEnumerable<RuleViolation> GetRuleViolations() {     return GetRuleViolations( ChangeAction.None ); }