/// <summary>
/// Builds a <see cref="FallbackPolicy"/> which provides a fallback action if the main execution fails. Executes the main delegate, but if this throws a handled exception, first calls <paramref name="onFallback"/> with details of the handled exception and the execution context; then calls <paramref name="fallbackAction"/>.
/// </summary>
/// <param name="policyBuilder">The policy builder.</param>
/// <param name="fallbackAction">The fallback action.</param>
/// <param name="onFallback">The action to call before invoking the fallback delegate.</param>
/// <exception cref="System.ArgumentNullException">fallbackAction</exception>
/// <exception cref="System.ArgumentNullException">onFallback</exception>
/// <returns>The policy instance.</returns>
public static FallbackPolicy Fallback(this PolicyBuilder policyBuilder, Action <Exception, Context, CancellationToken> fallbackAction, Action <Exception, Context> onFallback)
{
if (fallbackAction == null)
{
throw new ArgumentNullException(nameof(fallbackAction));
}
if (onFallback == null)
{
throw new ArgumentNullException(nameof(onFallback));
}
return(new FallbackPolicy(
(action, context, cancellationToken) => FallbackEngine.Implementation(
(ctx, ct) => { action(ctx, ct); return EmptyStruct.Instance; },
context,
cancellationToken,
policyBuilder.ExceptionPredicates,
PredicateHelper <EmptyStruct> .EmptyResultPredicates,
(outcome, ctx) => onFallback(outcome.Exception, ctx),
(outcome, ctx, ct) => { fallbackAction(outcome.Exception, ctx, ct); return EmptyStruct.Instance; }),
policyBuilder.ExceptionPredicates));
}
/// <summary>
/// Builds a <see cref="FallbackPolicy"/> which provides a fallback value if the main execution fails. Executes the main delegate, but if this throws a handled exception or raises a handled result, first calls <paramref name="onFallback"/> with details of the handled exception or result and the execution context; then calls <paramref name="fallbackAction"/> and returns its result.
/// </summary>
/// <param name="policyBuilder">The policy builder.</param>
/// <param name="fallbackAction">The fallback action.</param>
/// <param name="onFallback">The action to call before invoking the fallback delegate.</param>
/// <exception cref="System.ArgumentNullException">fallbackAction</exception>
/// <exception cref="System.ArgumentNullException">onFallback</exception>
/// <returns>The policy instance.</returns>
public static FallbackPolicy <TResult> Fallback <TResult>(this PolicyBuilder <TResult> policyBuilder, Func <DelegateResult <TResult>, Context, CancellationToken, TResult> fallbackAction, Action <DelegateResult <TResult>, Context> onFallback)
{
if (fallbackAction == null)
{
throw new ArgumentNullException(nameof(fallbackAction));
}
if (onFallback == null)
{
throw new ArgumentNullException(nameof(onFallback));
}
return(new FallbackPolicy <TResult>(
(action, context, cancellationToken) => FallbackEngine.Implementation <TResult>(
action,
context,
cancellationToken,
policyBuilder.ExceptionPredicates,
policyBuilder.ResultPredicates,
onFallback,
fallbackAction),
policyBuilder.ExceptionPredicates,
policyBuilder.ResultPredicates));
}