General Actions:
Last modified on August 15, 2012 17:21
The ability to intercept a validation chain while it is executing and possibly change validation behaviors and/or results is a surprisingly common requirement. To accomplish this DevForce provides a pluggable delegate that, if defined, will be called after the execution of each verifier within the validation chain. This is called a VerifierBatchInterceptor .
BatchInterceptor
A BatchInterceptor property is defined on the VerifierEngine.
| C# | public virtual VerifierBatchInterceptor BatchInterceptor { get; set; } |
| VB | Public Overridable Property BatchInterceptor() As VerifierBatchInterceptor |
The VerifierBatchInterceptor delegate is defined as:
| C# | public delegate VerifierErrorContinuationMode VerifierBatchInterceptor( object instance, TriggerContext triggerContext, VerifierContext verifierContext ) |
| VB | Public Delegate Function VerifierBatchInterceptor( _ ByVal instance As Object, ByVal triggerContext As TriggerContext, _ ByVal verifierContext As VerifierContext) As _ VerifierErrorContinuationMode _ Implements VerifierEngine.VerifierBatchInterceptor |
with the following VerifierErrorContinuationMode enum values:
| Value | Description |
|---|---|
| Stop | Stop executing, any verifiers further down the chain will be skipped. |
| Continue | Continue executing |
| Inherit | (See VerifierOptions inheritance discussion) |
Interception via the BatchInterceptor can be used to decide whether to continue with the current verification batch or to stop and return to the point in the program where the validation was triggered. The interception delegate also allows the currently executing validation's VerifierResultCollection to be modified. In other words, additional VerifierResults can be added or removed or summarized into a smaller number of VerifierResults after each verifier within the batch executes.
One example of its possible uses is to stop the verification process when the verification results already contains more than a maximum number of errors.
The following code sample below shows how you would create and use an interceptor.
| C# | public static VerifierErrorContinuationMode EmployeeBatchInterceptor(Object instance, TriggerContext triggerContext, VerifierContext verifierContext) { if (verifierContext.VerifierResults.Errors.Count > 10) { verifierContext.VerifierResults.Add( new VerifierResult(false, "Too many errors, stop immediately")); return VerifierErrorContinuationMode.Stop; } else { return VerifierErrorContinuationMode.Continue; } } public void DoEmployeeBatchInterceptor() { var mgr = new NorthwindIBEntityManager(); mgr.VerifierEngine.BatchInterceptor = EmployeeBatchInterceptor; mgr.VerifierEngine.DefaultVerifierOptions.ExecutionModes = VerifierExecutionModes.InstanceAndOnAfterSetTriggers; mgr.VerifierEngine.DefaultVerifierOptions.ErrorNotificationMode = VerifierErrorNotificationMode.Notify; var employee = mgr.Employees.FirstOrNullEntity(); employee.BirthDate = DateTime.Today.AddYears(7); //Verification batch will be executed here var results = mgr.VerifierEngine.Execute(employee); _localOutput.Append(results.Errors.Last().Message); } |
| VB | Public Shared Function EmployeeBatchInterceptor( _ ByVal instance As Object, ByVal triggerContext_Renamed As _ TriggerContext, ByVal verifierContext_Renamed As VerifierContext) _ As VerifierErrorContinuationMode If verifierContext_Renamed.VerifierResults.Errors.Count > 10 Then verifierContext_Renamed.VerifierResults.Add( _ New VerifierResult(False, "Too many errors, stop immediately")) Return VerifierErrorContinuationMode.Stop Else Return VerifierErrorContinuationMode.Continue End If End Function Public Sub DoEmployeeBatchInterceptor() Dim mgr = New NorthwindIBEntityManager() mgr.VerifierEngine.BatchInterceptor = _ AddressOf EmployeeBatchInterceptor mgr.VerifierEngine.DefaultVerifierOptions.ExecutionModes = _ VerifierExecutionModes.InstanceAndOnAfterSetTriggers mgr.VerifierEngine.DefaultVerifierOptions.ErrorNotificationMode _ = VerifierErrorNotificationMode.Notify Dim employee = mgr.Employees.FirstOrNullEntity() employee.BirthDate = Date.Today.AddYears(7) 'Verification batch will be executed here Dim results = mgr.VerifierEngine.Execute(employee) _localOutput.Append(results.Errors.Last().Message) End Sub |
VerifierContext.EndOfBatch
In addition to being fired after each verifier, the BatchInterceptor is also fired at the very end of the current verification batch. This is to provide useful behavior such as analyzing the results of the verification batch. Below is an example of the EmployeeBatchInterceptor delegate above modified by adding a simple logic using the VerifierContext.EndOfBatch property. The logic adds a new VerifierResult to the VerifierResultsCollection with a VerifierResultCode.Error and a string message to indicate how many total errors are accumulated at the end of batch.
| C# | public static VerifierErrorContinuationMode EmployeeBatchInterceptor( Object instance, TriggerContext triggerContext, VerifierContext verifierContext) { if (verifierContext.EndOfBatch) { verifierContext.VerifierResults.Add( new VerifierResult(VerifierResultCode.Error, String.Format("Accumulated a total of {0} error(s)", verifierContext.VerifierResults.Errors.Count))); return VerifierErrorContinuationMode.Stop; } else { if (verifierContext.VerifierResults.Errors.Count > 3) { verifierContext.VerifierResults.Add(new VerifierResult( VerifierResultCode.Error, "Too many errors, stop verification immediately")); return VerifierErrorContinuationMode.Stop; } else { return VerifierErrorContinuationMode.Continue; } } } |
| VB | Public Shared Function EmployeeBatchInterceptor(ByVal instance _ As Object, ByVal triggerContext_Renamed As TriggerContext, _ ByVal verifierContext_Renamed As VerifierContext) As _ VerifierErrorContinuationMode If verifierContext_Renamed.EndOfBatch Then verifierContext_Renamed.VerifierResults.Add( _ New VerifierResult(VerifierResultCode.Error, _ String.Format("Accumulated a total of {0} error(s)", _ verifierContext_Renamed.VerifierResults.Errors.Count))) Return VerifierErrorContinuationMode.Stop Else If verifierContext_Renamed.VerifierResults.Errors.Count > 3 Then verifierContext_Renamed.VerifierResults.Add( _ New VerifierResult(VerifierResultCode.Error, _ "Too many errors, stop verification immediately")) Return VerifierErrorContinuationMode.Stop Else Return VerifierErrorContinuationMode.Continue End If End If End Function |