I want to create a deep copy of an object. I chose to use the automapper because this way I dont have to edit classes and add there any extra code. Plus I use automapper for mapping my classes to DTOs.
On my surprise when I wanted to do a copy like:
var original = new TrainingSetDto()
var output = _mapper.Map<TrainingSetDto>(original);
the output variable retrieved reference to the original variable (shallow copy).
How to achieve my wanted result (deep copy of the original) to get new instance with same properties ?
E.g. on this blog
https://jshowers.com/create-deep-copies-of-object-in-c-using-automapper/
was mentioned that static call Mapper.Map<Person>(originalPerson); is the way how to do so. But these static methods are not there anymore.
Could you please point me to the right direction ?
As #LucianBargoanu pointed out it is possible to do a deep copy by AutoMapper.
By firstly specifying map for your object e.g.
CreateMap<TrainingSetDto, TrainingSetDto>();
and then just calling your mapping function
var copy = _mapper.Map<TrainingSetDto>(original);
I was able to reproduce the correct behavior in the Console app but in the API project it still didnt work correctly.
Finally the problem in the API project was in the dependency injection package: AutoMapper.Extensions.Microsoft.DependencyInjection. And thats why when I replaced:
services.AddAutoMapper(provider => new MapperConfiguration(cfg =>
{
cfg.AddProfile(new AutoMapperProfile());
cfg.AddMaps(Assembly.GetExecutingAssembly().GetReferencedAssemblies().Select(x => x.FullName));
}));
by:
services.AddSingleton(provider => new MapperConfiguration(cfg => {
cfg.AddProfile(new AutoMapperProfile());
cfg.AddMaps(Assembly.GetExecutingAssembly().GetReferencedAssemblies().Select(x => x.FullName));
}).CreateMapper());
it started to work correcly.
PS: I put my findings also to the discussion thread on AutoMapper github, but for some reason they deleted my comment and locked the thread.
I am wondering if there is a way to modify asserting value in the config.
For example,
I have the following assertion
customer.Should().Be(c, config => config.Excluding(c => c.Updated));
customer.Updated.Should().Be(c.Updated.ToString());
Is there any way to have conversion to string as part of the assertion instead of a separate assertion.
Something like this
customer.Should().Be(c, config => config.SomeFunction(c => c.Updated.ToString()))
According to the documentation here
Object graph comparison: Auto-Conversion
You should be able to instruct the assertion to
attempt to convert the value of a property of the subject-under-test to the type of the corresponding property on the expectation
customer.Should().BeEquivalentTo(c, options => options
.WithAutoConversionFor(x => x.Path.Contains("Updated")));
or
customer.Should().BeEquivalentTo(c, options => options.WithAutoConversion());
Ok folks, this is a rather long question, where I´m trying my best to describe the current situation and provide some meaningful context, before I´m comming to my actual question.
TL;DR;
I need a way to identify invalid enum-to-enum mappings, which might cause runtime-issues, as their definitions diverged over the time.
Some Context
So my team and I are maintaining this rather complex set of REST-APIs...complex at least when it comes down to the actual object-graphs involved.
We have to deal with some hundreds of models in total.
To raise structural complexity, the original architectures went with full n-tier-style on an inner API-level.
On top of that, we´re having multiple of such architectured services, which sometimes need calling each other.
This is achieved through either ordinary http-calls here, some messaging there, you get the idea.
For letting an API communicate with another, and to maintain SOA- and/or microservice-principles, every API at least provides a corresponding client-library, which manages communication with it´s representing API, regardless of the actual underlying protocol involved.
Boiling this down, this incorporates at least the following layers per API (top-down)
Client-Layer
API-Layer
Domain-Layer
Persistence-Layer
Additionally, all those layers maintain their own representation of the various models. Often, those are 1:1 representation, just in another namespace. Sometimes there are more significant differences in between these layers. It depends...
To reduce boiler-plate when communicating between these layers, we´re falling back on AutoMapper most of the time (hate it or love it).
The problem:
As we evolve our overall system, we more and more noticed problems when mapping enum-to-enum properties within the various representations of the models.
Sometimes it´s because some dev just forgot to add a new enum-value in one of the layers, sometimes we re-generated an Open-API based generated client, etc., which then leads to out-of-sync definitions of those enums. The primary issue is, that a source enum may have more values then the target enum.
Another issue might occur, when there are slight differences in the naming, e.g. Executer vs. Executor
Let´s say we have this (very very over-simplified) model-representations
public enum Source { A, B, C, D, Executer, A1, B2, C3 } // more values than below
public enum Destination { C, B, X, Y, A, Executor } //fewer values, different ordering, no D, but X, Y and a Typo
class SourceType
{
public Source[] Enums { get; set; }
}
class DestinationType
{
public Destination[] Enums { get; set; }
}
Now let´s say our AutoMapper config looks something like this:
var problematicMapper = new MapperConfiguration(config =>
{
config.CreateMap<SourceType, DestinationType>();
}).CreateMapper();
So mapping the following model is kind of a jeopardy, semantic-wise (or at least offers some very odd fun while debugging).
var destination = problematicMapper.Map<DestinationType>(new SourceType()
{
Enums = new []
{
Source.A,
Source.B,
Source.C,
Source.D,
Source.Executer,
Source.A1,
Source.B2,
Source.C3
}
});
var mappedValues = destination.Enums.Select(x => x.ToString()).ToArray();
testOutput.WriteLine(string.Join(Environment.NewLine, mappedValues));
/*
Source.A => A <- ✔️ ok
Source.B => b <- ✔️ok
Source.C => c <- ✔️ok
Source.D => Y <- 🤷♀️ whoops
Source.Executer => A <- 🧏♂️ wait, what?
Source.A1 => Executor <- 🙊 nah
Source.B2 => 6 <- 🙉 wtf?
Source.C3 => 7 <- 🙈 wth?
*/
bare with me, as some situations here are staged and possibly more extreme than found in reality. Just wanted to point out some weird behavior, even with AutoMapper trying to gracefully handle most cases, like the re-orderings or different casings. Currently, we are facing either more values in the source-enum, or slightly differences in naming / typos
Fewer fun can be observed, when this ultimately causes some nasty production-bugs, which also may have more or less serious business-impact - especially when this kind of issue only happens during run-time, rather than test- and/or build-time.
Additionally, the problem is not exclusive to n-tier-ish architectures, but could also be an issue in orthogonal/onion-/clean-ish-architecture styles (wheras in such cases it should be more likely that such value-types would be placed somewhere in the center of the APIs, rather than on every corner / outer-ring /adapter-layer or whatever the current terminology is)
A (temporary) solution
Despite trying to reduce the shear amount of redundancy within the respective layers, or (manually) maintaining explicit enum-values within the definitions itself (which both are valid options, but heck, this is a lot of PITA-work), there is not much left to do while trying to mitigate this kind of issues.
Gladly, there is a nice option available, which levereages mapping enum-to-enum-properties per-name instead of per-value, as well as doing more customization on a very fine-granular level on a per-member-basis.
[AutoMapper.Extensions.EnumMapping] to the rescue!
from the docs:
The package AutoMapper.Extensions.EnumMapping will map all values from Source type to Destination type if both enum types have the same value (or by name or by value)
and
This package adds an extra EnumMapperConfigurationExpressionExtensions.EnableEnumMappingValidation extension method to extend the existing AssertConfigurationIsValid() method to validate also the enum mappings.
To enable and cusomize mappings, one should just need to create the respective type-maps within AutoMapper-configuration:
var mapperConfig = new MapperConfiguration(config =>
{
config.CreateMap<SourceType, DestinationType>();
config.CreateMap<Source, Destination>().ConvertUsingEnumMapping(opt => opt.MapByName());
config.EnableEnumMappingValidation();
});
mapperConfig.AssertConfigurationIsValid();
Which then would validate even enum-to-enum mappings.
The question (finally ^^)
As our team previously did not (need to) configure AutoMapper with maps for every enum-to-enum mapping (as was the case for dynamic-maps in previous-versions of AutoMapper), we´re a bit lost on how to efficiently and deterministically discover every map needed to be configured this way. Especially, as we´re dealing with possibly a couple of dozens of such cases per api (and per layer).
How could we possibly get to the point, where we have validated and adapted our existing code-base, as well as further preventing this kind of dumbery in the first place?
Leverage custom validation to discover missing mappings during test-time
Ok, now this approach leverages a multi-phased analysis, best fitted into an unit-test (which may already be present in your solution(s), nevertheless).
It´s not a golden gun to magically solve all your issues which may be prevalent, but puts you into a very tight dev-loop which should help clean up things.
Period.
The steps involved are
enable validation of your AutoMapper-configuration
use AutoMapper custom-validation to discover missing type maps
add and configure missing type-maps
ensure maps are valid
adapt changes in enums, or mapping logic (whatever best fits)
this can be cumbersome and needs extra attention, depending on the issues discovered by this approach
rinse and repeat
Examples below use xUnit. Use whatever you might have at hands.
0. starting point
We´re starting with your initial AutoMapper-configuration:
var mapperConfig = new MapperConfiguration(config =>
{
config.CreateMap<SourceType, DestinationType>();
});
1. enable validation of your AutoMapper-Configuration
Somewhere within your test-suit, ensure you are validating your AutoMapper-configuration:
[Fact]
public void MapperConfigurationIsValid() => mapperConfig.AssertConfigurationIsValid();
2. use AutoMapper custom-validation to discover missing type maps
Now modify your AutoMapper-configuration to this:
mapperConfig = new MapperConfiguration(config =>
{
config.CreateMap<SourceType, DestinationType>();
config.Advanced.Validator(context => {
if (!context.Types.DestinationType.IsEnum) return;
if (!context.Types.SourceType.IsEnum) return;
if (context.TypeMap is not null) return;
var message = $"config.CreateMap<{context.Types.SourceType}, {context.Types.DestinationType}>().ConvertUsingEnumMapping(opt => opt.MapByName());";
throw new AutoMapperConfigurationException(message);
});
config.EnableEnumMappingValidation();
});
This does a couple of things:
look for mappings, that map from an enum to an enum
which have no type-map associated to them (that is, they were "generated" by AutoMapper itself and hence are lacking an explicit CreateMap call)
if (!context.Types.DestinationType.IsEnum) return;
if (!context.Types.SourceType.IsEnum) return;
if (context.TypeMap is not null) return;
Raise an error, which message is the equivalent of the actual call missing to CreateMap
var message = $"config.CreateMap<{context.Types.SourceType}, {context.Types.DestinationType}>().ConvertUsingEnumMapping(opt => opt.MapByName());";
throw new AutoMapperConfigurationException(message);
3. add and configure missing type-maps
Re-running our previous test, which should fail now, should output something like this:
AutoMapper.AutoMapperConfigurationException : config.CreateMap<Sample.AutoMapper.EnumValidation.Source, Sample.AutoMapper.EnumValidation.Destination>().ConvertUsingEnumMapping(opt => opt.MapByName());
And boom, there you go. The missing type-map configuration call on a silver-plate.
Now copy that line and place it somewhere suitable withing your AutoMapper-configuration.
For this post I´m just putting it below the existing one:
config.CreateMap<SourceType, DestinationType>();
config.CreateMap<Sample.AutoMapper.EnumValidation.Source, Sample.AutoMapper.EnumValidation.Destination>().ConvertUsingEnumMapping(opt => opt.MapByName());
in a real-world scenario, this would be a line for every enum-to-enum mapping that not already has a type-map associated to it within the AutoMapper-configuration. Depending on how you actually configure AutoMapper, this line could need to be slightly adopted to your needs, e.g. for usage in MappingProfiles.
adapt changes in enums
Re-run the test from above, which should fail now, too, as there are incompatible enum-values.
The output should look something like this:
AutoMapper.AutoMapperConfigurationException : Missing enum mapping from Sample.AutoMapper.EnumValidation.Source to Sample.AutoMapper.EnumValidation.Destination based on Name
The following source values are not mapped:
- B
- C
- D
- Executer
- A1
- B2
- C3
There you go, AutoMapper discovered missing or un-mappable enum-values.
note that we lost automatic handling of differences in casing.
What´s to do now heavily depends on your solution and cannot be covered in a SO-post. So take appropriate actions to mitigate.
6. rinse and repeat
Go back to 3. until all issues are solved.
From then on, you should have a saftey-net in place, that should prevent you from falling into that kind of trap in the future.
However, note that mapping per-name instead of per-value might have a negative impact, performance-wise. That should definetley be taken into account when applying this kind of change to your code-base. But with all those inter-layer-mappings present I would guess a possible bottleneck is in another castle, Mario ;)
A full wrapup of the samples shown in this post can be found in this github-repo
I wrote a validator that would check if the Enums match so I don't have to add those Enum Mappings.
var problematicMapperConfiguration = new MapperConfiguration(config =>
{
config.Advanced.Validator(EnumMappingValidator.ValidateNamesMatch());
config.CreateMap<SourceType, DestinationType>();
});
problematicMapperConfiguration.AssertConfigurationIsValid();
With your example it would fail like that:
Expected enum AutoMapperEnumValidation.EarlocTests+Destination to contain enum "D".
Expected enum AutoMapperEnumValidation.EarlocTests+Destination to contain enum "Executer".
Expected enum AutoMapperEnumValidation.EarlocTests+Destination to contain enum "A1".
Expected enum AutoMapperEnumValidation.EarlocTests+Destination to contain enum "B2".
Expected enum AutoMapperEnumValidation.EarlocTests+Destination to contain enum "C3".
The validator is very simple and looks like this:
public class EnumMappingValidator
{
public static Action<ValidationContext> ValidateNamesMatch()
{
return validationContext =>
{
var sourceEnumType = GetEnumType(validationContext.Types.SourceType);
if (sourceEnumType == null)
return;
var destinationEnumType = GetEnumType(validationContext.Types.DestinationType);
if (destinationEnumType == null) throw new ArgumentException("Unexpected Enum to Non-Enum Map");
var sourceEnumNames = sourceEnumType.GetFields().Select(x => x.Name).ToList();
var destinationEnumNames = destinationEnumType.GetFields().Select(x => x.Name).ToList();
var errors = new List<string>();
foreach (var sourceEnumName in sourceEnumNames)
{
if (destinationEnumNames.All(x => x.ToLower() != sourceEnumName.ToLower()))
errors.Add($"Expected enum {destinationEnumType} to contain enum \"{sourceEnumName}\".");
}
if (errors.Any())
throw new ArgumentException(string.Join(Environment.NewLine, errors));
};
}
private static Type? GetEnumType(Type type)
{
if (type.IsEnum) return type;
var nullableUnderlyingType = Nullable.GetUnderlyingType(type);
if (nullableUnderlyingType?.IsEnum ?? false) return nullableUnderlyingType;
return null;
}
}
Github: https://github.com/matthiaslischka/AutoMapperEnumValidation
Is it possible to disable the built-in mapper for enums in AutoMapper, or replace it with one that always throws an exception?
I find the built in mapper to be highly unreliable as it will try it's best to map an input to any enum you give it which increases the risk of introducing, difficult to trace, bugs in your code.
I'd much rather have it fail with an exception telling me that I'm missing a mapper/converter than have it just work and then several steps down the call stack the code fails because the value isn't right in the current context.
Based on the comment from Lucian i added the following code to my configuration:
services.AddAutoMapper(config =>
{
var enumMapper = config.Mappers.Single(m => m is AutoMapper.Mappers.EnumToEnumMapper);
config.Mappers.Remove(enumMapper);
}, typeof(Startup));
This removes the default EnumToEnum mapper and gives me the exception when no mapping is configured.
From what you write I can think of a few options:
If you have an enum property on an object, you can ignore it
explicitly by using:
CreateMap<Foo, Bar>().ForMember(dest => dest.EnumProperty, opt => opt.Ignore());
If you create mappings for the properties you want to map and leave out the enum properties you can use:
CreateMap<Foo, Bar>().ForMember(...).ForAllOtherMembers(opt => opt.Ignore())
If you want to replace the mapping between to enum types you can overwrite it with:
Mapper.CreateMap<EnumSrc,EnumDst>().ConvertUsing(value => {
throw new Exception();
});
I have a public class called Profile. Very simple model class currently with 2 properties; string Name and string Fields. As I develop the project the class will expand but it's not particularly important at the moment.
I have a Global static IList of type Profile called Profiles. I am quite new to manipulating the data in these IEnumerable types but I am looking to update one of the properties of a single profile. I have tried the following but I am receiving an object reference not set exception. The following is where I set the property:
Profiles.Single(x => x.Name == listBoxProfiles.Text).Fields = textBoxFieldName.Text;
The debugger is showing the listbox and textbox text properties both have the correct values so I think that it is the way I am using single that is wrong.
If anyone could shed some light I would be grateful.
A simple amendment to make the code more defensive is all that is required:
var profile = Profiles.SingleOrDefault(x => x.Name == listBoxProfiles.Text);
if (profile != null)
{
profile.Fields = textBoxFieldName.Text;
}
else
{
Profiles.Add(new Profile(textBoxFieldName.Text));
}
This code will cope with missing values, SingleOrDefault expects 0 or 1 items to be returned. It will throw an exception if more than 1 items are found.
If you know your code should always have the item you are looking for, then your code will work - but I'd advise against this style of programming in favour of being a little more defensive.