/// <summary>
/// Starts a validation asynchronously and returns a Task for the operation.
/// </summary>
/// <typeparam name="TTarget"> The type of the object to validate. </typeparam>
/// <param name="plan"> The validation plan to execute asynchronously. </param>
/// <param name="target"> The type of the object to validate. </param>
/// <returns> </returns>
public static Task <ValidationReport> ExecuteAsync <TTarget>(
this ValidationPlan <TTarget> plan,
TTarget target)
{
var tcs = new TaskCompletionSource <ValidationReport>(target);
var scope = new ValidationScope(enter: false);
Task.Factory.StartNew(() =>
{
var taskDictionary =
new ConcurrentDictionary <IValidationRule <TTarget>, Task <bool> >();
// create and start a task for each rule
plan.Select(
rule => taskDictionary.GetOrAdd(rule,
rule.ToTask(target,
taskDictionary,
scope,
TaskCreationOptions.AttachedToParent)))
.ForEach(t => t.TryStart());
})
.ContinueWith(t =>
{
try
{
tcs.Complete(t, () => ValidationReport.FromScope(scope));
}
finally
{
scope.Dispose();
}
});
return(tcs.Task);
}
/// <summary>
/// Determines whether the specified target is valid.
/// </summary>
/// <param name="target"> The target. </param>
/// <returns> <c>true</c> if the specified target is valid; otherwise, <c>false</c> . </returns>
public bool Check(TTarget target)
{
using (var scope = new ValidationScope {
Rule = this
})
{
return(Check(target, scope));
}
}
/// <summary>
/// Determines (synchronously) whether the specified target is valid.
/// </summary>
/// <param name="target"> The object to be validated. </param>
/// <param name="scope"> The <see cref="ValidationScope" /> in which to perform the validation. </param>
/// <returns> <c>true</c> if the specified target is valid; otherwise, <c>false</c> . </returns>
public override bool Check(TTarget target, ValidationScope scope)
{
var task = TaskFor(target, scope).TryStart();
if (task.Status == TaskStatus.WaitingForActivation)
{
throw new InvalidOperationException("The rule cannot be evaluated because its task is dependent on another task that has not been started.");
}
return(task.Result);
}
/// <summary>
/// Performs the actual rule check.
/// </summary>
protected override bool PerformCheck(TTarget target, ValidationScope scope = null)
{
using (scope = new ValidationScope(scope)
{
Rule = this
})
{
return(scope.HaltsOnFirstFailure
? EvaluationStrategy <TTarget> .HaltOnFirstFailure.Evaluate(this, target, scope)
: Strategy.Evaluate(this, target, scope));
}
}
/// <summary>
/// Exit the specified <paramref name="scope" /> .
/// </summary>
/// <remarks>
/// If there are nested scopes within the specified <paramref name="scope" /> , those will be exited as well.
/// </remarks>
/// <param name="scope"> The scope to exit </param>
protected static void ExitScope(ValidationScope scope)
{
if (!ActiveScopes.Contains(scope))
{
return;
}
ValidationScope popped;
do
{
popped = ActiveScopes.Pop();
} while (scope != popped);
}
/// <summary>
/// Determines whether the specified target is valid.
/// </summary>
/// <param name="target"> The target. </param>
/// <param name="scope"> The ValidationScope for the operation. </param>
/// <returns> <c>true</c> if the specified target is valid; otherwise, <c>false</c> . </returns>
public virtual bool Check(TTarget target, ValidationScope scope)
{
// when there is no active ValidationScope, simply perform the check
if (scope == null)
{
if (preconditions != null && preconditions.Any(rule => !rule.Check(target)))
{
// this rule is considered to have succeeded, i.e. not failed, because it has not been evaluated, so return true:
return(true);
}
return(PerformCheck(target, scope));
}
if (CheckPreconditions(scope.Parent ?? scope, target))
{
return(true);
}
// get the result of the rule
var result = PerformCheck(target, scope);
var messageGenerator = MessageGenerator ?? scope.MessageGenerator;
// extract paramaters from the scope and store them if needed in a FailedEvaluation
var parameters = scope.FlushParameters();
if (!result)
{
// record the failure in the ValidationScope
scope.AddEvaluation(new FailedEvaluation(target, this, messageGenerator)
{
IsInternal = CreatesEvaluationsAsInternal,
Parameters = parameters
});
}
else
{
scope.AddEvaluation(new SuccessfulEvaluation(target, this, messageGenerator)
{
IsInternal = CreatesEvaluationsAsInternal,
Parameters = parameters
});
}
return(result);
}
/// <summary>
/// Initializes a new instance of the <see cref="ValidationScope" /> class.
/// </summary>
public ValidationScope(bool enter = true)
{
if (activeScopes != null && activeScopes.Count > 0)
{
parent = ActiveScopes.Peek();
evaluations = parent.evaluations;
}
else
{
evaluations = new ConcurrentBag <RuleEvaluation>();
}
if (enter)
{
EnterScope(this);
}
}
private Func <TTarget, ValidationScope, Task <bool> > CreateTask(Func <TTarget, Task <TTarget> > setup, Func <TTarget, bool> validate) =>
(target, parentScope) =>
{
var tcs = new TaskCompletionSource <bool>();
var task = setup(target);
task.ContinueWith(
t => tcs.Complete(t,
() =>
{
using (var scope = new ValidationScope(parentScope))
{
var result = validate(t.Result);
RecordResult(scope, result, target);
return(result);
}
}));
return(tcs.Task);
};
public Task <bool> TaskFor(TTarget target, ValidationScope scope)
{
var tcs = new TaskCompletionSource <bool>();
Task.Factory
.StartNew(() =>
{
// TODO: (TaskFor) prevent setup from running if a precondition failed. IsPreconditionUnsatisfied may not be appropriate for async since it forces evaluation when it finds an unevaluated precondition.
// if (CheckPreconditions(scope, target))
// {
// tcs.SetCanceled();
// return;
// }
taskFactory(target, scope).TryStart();
});
return(tcs.Task);
}
/// <summary>
/// Evaluates all constituent validation rules against the specified target.
/// </summary>
/// <param name="target"> The target. </param>
/// <param name="haltOnFirstFailure"> When true, stops execution on the first failed rule </param>
/// <returns> </returns>
public ValidationReport Execute(TTarget target, bool haltOnFirstFailure = false)
{
using (var scope = new ValidationScope {
MessageGenerator = MessageGenerator, Rule = this
})
{
if (haltOnFirstFailure)
{
scope.HaltsOnFirstFailure = true;
}
foreach (var rule in rules)
{
var ruleTemp = rule;
if (!scope.HasFailed(target, ruleTemp))
{
var success = rule.Check(target);
// ValidationRule<TTarget> handles this internally but otherwise add it to the scope.
if (!(rule is ValidationRule <TTarget>))
{
if (!success)
{
scope.AddEvaluation(new FailedEvaluation(target, rule, MessageGenerator));
}
else
{
scope.AddEvaluation(new SuccessfulEvaluation(target, rule, MessageGenerator));
}
}
}
if (scope.ShouldHalt())
{
break;
}
}
return(ValidationReport.FromScope(scope));
}
}
private void RecordResult(ValidationScope scope, bool result, TTarget target)
{
var parameters = scope.FlushParameters();
var messageGenerator = scope.MessageGenerator;
if (result)
{
scope.AddEvaluation(new SuccessfulEvaluation(target, this)
{
MessageGenerator = messageGenerator,
Parameters = parameters
});
}
else
{
scope.AddEvaluation(new FailedEvaluation(target, this)
{
MessageGenerator = messageGenerator,
Parameters = parameters
});
}
}
private static Task <bool> ToTask <T>(
this IValidationRule <T> forRule,
T target,
ConcurrentDictionary <IValidationRule <T>, Task <bool> > tasks,
ValidationScope scope,
TaskCreationOptions options = TaskCreationOptions.PreferFairness)
{
// if the rule is inherently capable of async, let it build the task
var asyncRule = forRule as AsyncValidationRule <T>;
if (asyncRule != null)
{
return(asyncRule.TaskFor(target, scope));
}
// otherwise, build a task from its tree
var task = new Task <bool>(
() =>
{
var rule = forRule as ValidationRule <T>;
// there are preconditions, so each will need its own task, and main task must wait on them all
rule?.preconditions
.ForEach(pre => tasks.GetOrAdd(rule,
_ => pre.ToTask(target,
tasks,
scope,
TaskCreationOptions.AttachedToParent)));
using (var innerScope = new ValidationScope(scope))
{
return(forRule.Check(target, innerScope));
}
}, options);
return(task);
}
internal static ValidationReport FromScope(ValidationScope scope) => new ValidationReport(scope.Evaluations);
/// <summary>
/// Enters the specified <paramref name="scope" /> .
/// </summary>
/// <param name="scope"> The scope. </param>
protected static void EnterScope(ValidationScope scope)
{
ActiveScopes.Push(scope);
}
/// <summary>
/// Initializes a new instance of the <see cref="ValidationScope" /> class.
/// </summary>
/// <param name="parent"> The parent. </param>
public ValidationScope(ValidationScope parent)
{
this.parent = parent;
evaluations = parent.evaluations;
EnterScope(this);
}
/// <summary> /// Performs the actual rule check. /// </summary> protected virtual bool PerformCheck(TTarget target, ValidationScope scope = null) => condition(target);
protected bool CheckPreconditions(ValidationScope scope, TTarget target)
{
if (preconditions == null)
{
return(false);
}
// check previously-evaluated preconditions. any occurrence of the same combination of rule and target will short circuit the current operation.
if (scope.AllFailures.Any(f =>
preconditions.Any(pre =>
Equals(f.Target, target) &&
ValidationRuleComparer.Instance.Equals(pre, f.Rule))))
{
// this failure indicates a short-circuited precondition. this mechanism identifies preconditions of preconditions.
// TODO: (CheckPreconditions) mark the failure so that it can be identified as such for debug purposes
scope.AddEvaluation(new FailedEvaluation(target, this)
{
IsInternal = true
});
return(true);
}
// check unevaluated preconditions
foreach (var rule in preconditions)
{
var tempRule = rule;
if (!scope.Evaluations.Any(ex => Equals(ex.Target, target) &&
ValidationRuleComparer.Instance.Equals(ex.Rule, tempRule)))
{
using (var internalScope = new ValidationScope {
Rule = this
})
{
internalScope.RuleEvaluated += (s, e) =>
{
var failure = e.RuleEvaluation as FailedEvaluation;
if (failure != null)
{
failure.IsInternal = true;
}
};
if (!rule.Check(target))
{
return(true);
}
}
// finally we have to check if the rule's preconditions were in turn unsatisfied.
var vRule = rule as ValidationRule <TTarget>;
if (vRule != null)
{
if (vRule.CheckPreconditions(scope, target))
{
return(true);
}
}
}
}
return(false);
}
public virtual bool Evaluate(IEnumerable <IValidationRule <T> > rules, T target, ValidationScope scope) => evaluate(rules, target, scope);
