// If an already invalid child is set or the previous child was invalid,
// the aggregated validation state of the owner changes, therefore an
// ValidationResultChanged event should be raised.
private void DetectValidationResultChange(IBehaviorContext context, Action action)
{
IViewModel oldChild = this.GetValueNext <TValue>(context);
action();
IViewModel newChild = this.GetValueNext <TValue>(context);
// It is important to query the 'oldResult' after executing the 'action'. The
// following scenario could happen otherwise:
// 1. 'oldResult' is assigned before the action and is valid.
// 2. The action is executed and makes 'oldChild' invalid and 'newChild'
// stays valid. Since 'oldChild' is still in the hierarchy at this
// time, the error is propagated to the validation caches of the
// parent.
// 3. 'newResult' is assigned to result of the 'newChild' (valid).
// 4. We would not detect a change in the 'if' below and therefore not
// raise a change which would leave the validation cache of the parents
// with the stale error.
ValidationResult oldResult = GetValidationResultOrValidIfNull(oldChild);
ValidationResult newResult = GetValidationResultOrValidIfNull(newChild);
if (!Object.Equals(oldResult, newResult))
{
context.NotifyChange(ChangeArgs.ValidationResultChanged());
}
}
public void HandleChange(IBehaviorContext context, CollectionChangedArgs <TItemVM> args)
{
IEnumerable <TItemVM> changedItems = args
.OldItems
.Concat(args.NewItems);
IEnumerable <ValidationResult> changedItemsResults = changedItems
.Select(x => x.Kernel.GetValidationResult());
var changedItemsResult = ValidationResult.Join(changedItemsResults);
this.HandleChangeNext(context, args);
// If already invalid items are added or removed, the aggregated
// validation state of the collection owner changes, therefore an
// ValidationResultChanged event should be raised.
if (!changedItemsResult.IsValid)
{
context.NotifyChange(ChangeArgs.ValidationResultChanged(args.Reason));
}
}
public override void InitializeValue(IBehaviorContext context)
{
base.InitializeValue(context);
TValue childVM = this.GetValueNext <TValue>(context);
if (childVM != null)
{
ValidationResult childValidatonResult = childVM
.Kernel
.GetValidationResult();
if (!childValidatonResult.IsValid)
{
// If 'PopulatedWith' returns an already invalid item, the aggregated
// validation state of the collection owner changes, therefore an
// 'ValidationResultChanged' event should be raised.
if (!childValidatonResult.IsValid)
{
context.NotifyChange(ChangeArgs.ValidationResultChanged());
}
}
}
}
