Update: the set of test results in this blog didn’t turn out to all be based on fair comparisons - I’ve updated them and re-measured. I’m leaving this blog in place as it describes the tests.

This is the first in a series of posts comparing a subset of the available mappers. I’m going to compare performance, features and ease of use, and I’ll turn those words into links as I write the blogs. This blog is on that favourite thing we’re not supposed to obsess too much about (in programming) - performance.

The Mappers

AgileMapper

My mapper project which I first published last month. AgileMapper focuses on ease of use, flexibility and transparency.

AutoMapper

343 thousand downloads of the latest version; pretty safe to say you all already know about AutoMapper, right? Not much else to say, then :)

ExpressMapper

ExpressMapper is a ‘lightweight’ mapper, first written as a faster alternative to the AutoMapper 4.x.x series.

Mapster

Mapster is another ‘lightweight’ mapper, written to be “kind of like AutoMapper, just simpler and way, way faster” (quoted from their NuGet page).

ValueInjecter

ValueInjecter is written for flexibility, and supports unflattening as well as flattening.

The Tests

The performance test project is a console project based on the AutoMapper benchmark which performs each of the following, for each mapper, 1 million times:

• Constructor mapping - creating a POCO with a single constructor parameter from a POCO with a matching property

• Complex mapping - deep cloning a Foo POCO with various kinds of value type properties, multiply-recursive Foo, List<Foo> and Foo[] properties, and IEnumerable<int> and int[] properties

• Flattening - mapping from a POCO with nested POCO properties to a POCO with all value type (and string) properties

• Unflattening - mapping from a POCO with all value type (and string) properties to an object with nested POCO properties - only AgileMapper and ValueInjecter support this at the time of writing

• Deep mapping - mapping a POCO with nested POCO and POCO collection properties onto a differently-typed POCO with corresponding properties

An aside about Unflattening

As it turned out, it was only AgileMapper and ValueInjecter that supported the unflattening scenario. AutoMapper has limited configurable support for unflattening, but can’t - or at least I couldn’t figure out how it could - map to two different nested POCO properties of the same type. Not a knock against AutoMapper - it’s just not what it’s made for.

The Results!

I bet at least some of you skipped to this bit :) That’s ok! :) Here’s the results I got - the numbers are the total elapsed seconds for 1 million mappings of each type. I used the latest versions of each mapper.

Points to Note

• Mapster is the fastest!

• At this point I’d say AgileMapper’s performance is ‘comparable’ - faster than some, slower than others. I’m pretty happy with that having worked on it as a pet project over the last 6ish months

• The performance improvements in AutoMapper 5 were huge; benchmarks you may find against the much-slower version 4 are pretty much irrelevant

• Obviously some of the ValueInjecter numbers look like outliers - the test classes can be viewed here; if there’s a better way I could have set them up please do let me know and I’ll be happy to say so!

I’ll continue making performance tweaks as I continue with AgileMapper - in the meantime stay tuned for comparisons of features and ease of use.

Update: the set of test results in this blog didn’t turn out to all be based on fair comparisons - I’ve updated them and re-measured. I’m leaving this blog in place as it describes the tests.