Information Technology Reference
In-Depth Information
url => startDownload(url),
task => finishDownload(task.AsyncState.ToString(),
task.Result));
}
catch
(
AggregateException
problems)
{
var
handlers =
new
Dictionary
<
Type
,
Action
<
Exception
>>();
handlers.Add(
typeof
(
WebException
),
ex =>
Console
.WriteLine(ex.Message));
if
(!HandleAggregateError(problems, handlers))
throw
;
}
The HandleAggregateError method recursively looks at every exception. If the
exception is expected, the handler is called. Otherwise, HandleAggregateError
returns false, indicating that this set of aggregate exceptions cannot be
processed correctly.
private static bool
HandleAggregateError(
AggregateException
aggregate,
Dictionary
<
Type
,
Action
<
Exception
>> exceptionHandlers)
{
foreach
(
var
exception
in
aggregate.InnerExceptions)
if
(exception
is
AggregateException
)
return
HandleAggregateError(
exception
as
AggregateException
,
exceptionHandlers);
else if
(exceptionHandlers.ContainsKey(
exception.GetType()))
{
exceptionHandlers[exception.GetType()]
(exception);
}
else
return false
;
return true
;
}
This code does look a bit dense, but it's not that hard. When it encounters
an AggregateException, it evaluates that child list recursively. When it
