I have a method which can be written pretty neatly through method chaining:
return viewer.ServerReport.GetParameters()
.Single(p => p.Name == Convention.Ssrs.RegionParamName)
.ValidValues
.Select(v => v.Value);
However I'd like to be able to do some checks at each point as I wish to provide helpful diagnostics information if any of the chained methods returns unexpected results.
To achieve this, I need to break up all my chaining and follow each call with an if
block. It makes the code a lot less readable.
Ideally I'd like to be able to weave in some chained method calls which would allow me to handle unexpected outcomes at each point (e.g. throw a meaningful exception such as new ConventionException("The report contains no parameter")
if the first method returns an empty collection). Can anyone suggest a simple way to achieve such a thing?
Edit:
This is the result of using @JeffreyZhao's answer:
return viewer.ServerReport.GetParameters()
.Assert(result => result.Any(), "The report contains no parameter")
.SingleOrDefault(p => p.Name == Convention.Ssrs.RegionParamName)
.Assert(result => result != null, "The report does not contain a region parameter")
.ValidValues
.Select(v => v.Value)
.Assert(result => result.Any(), "The region parameter in the report does not contain any valid value");
Maybe you can use this approach.
static T Check<T>(this T value)
{
if (...) throw ...;
return value;
}
then:
xxx.Single(...).Check().Select(...).Check()...
Update:
You can even:
static T Validate<T>(this T value, Func<T, bool> validate, string errorMessage)
{
if (!validate(value))
throw new ValidationFailedException(errorMessage);
return value;
}
then:
xxxx.Single()
.Validate(v => v > 0, "Must be greater than zero")
.NextStep()
.Validate(...);