Expression mapping fails on one specific machine.

[Baune8D]

Source/destination types

protected async Task<TEntity> GetEntityByDtoAsync(TDto dto)
{
    var mappedExpression = _mapper.Map(dto, typeof(TDto), typeof(Expression<Func<TEntity, bool>>));
    if (!(mappedExpression is Expression<Func<TEntity, bool>> equivExpr)) return null;
    return await DbSet.SingleOrDefaultAsync(equivExpr);
}

Mapping configuration

public static void ConfigureAutoMapper(this IServiceCollection services, Assembly assemblyToScan = null)
{
    var mappingAssembly = typeof(UserProfile).Assembly;

    services.AddAutoMapper(cfg =>
    {
        if (assemblyToScan != null)
        {
            cfg.AddProfiles(mappingAssembly, assemblyToScan);
        }
        else
        {
            cfg.AddProfiles(mappingAssembly);
        }
        cfg.AddCollectionMappers();
        cfg.SetGeneratePropertyMaps<GenerateEntityFrameworkPrimaryKeyPropertyMaps<CustomDbContext>>();
    });
}

Version: x.y.z

AutoMapper v6.2.2
AutoMapper.Collection v3.1.3
AutoMapper.Collection.EntityFramework v3.1.3
AutoMapper.EF6 v1.1.1
AutoMapper.Extensions.Microsoft.DependencyInjection v3.2.0

Application is a ASP.NET Core 2.0 web app using .NET Framework 4.7.1

Expected behavior

var mappedExpression = _mapper.Map(dto, typeof(TDto), typeof(Expression<Func<TEntity, bool>>));

This line works perfectly fine on my development machine. (Windows 10)

Actual behavior

Same line fails on our test server (Windows Server 2012 R2).
It fails with the following exception:

An unhandled exception occurred while processing the request.
AutoMapperConfigurationException: 
Unmapped members were found. Review the types and members below.
Add a custom mapping expression, ignore, add a custom resolver, or modify the source/destination type
For no matching constructor, add a no-arg ctor, add optional arguments, or map all of the constructor parameters
=====================================================================================================================================================================================================================================================================================================================================================================================
ConversationDto -> Expression`1 (Destination member list)
Organization.Domain.DTOs.ConversationDto -> System.Linq.Expressions.Expression`1[[System.Func`2[[Organization.CodeFirst.Models.Conversation, Organization.CodeFirst, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[System.Boolean, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] (Destination member list)

Unmapped properties:
Parameters
No available constructor.
AutoMapper.ConfigurationValidator.AssertConfigurationIsValid(IEnumerable<TypeMap> typeMaps)

Steps to reproduce

I cannot reproduce this as it only happens on our test server. I have tried using the exact same application produced with 'dotnet publish' and it works fine on one machine but fails on another.
I am completely lost and have spent days on this problem. Is there anything in AutoMapper that could be dependent on something OS specific?

[lbargaoanu]

You need to isolate the issue. You shouldn't call AssertConfigurationIsValid in production. Its purpose is to help during development.

[Baune8D]

@lbargaoanu I dont call Assert. App crashes with the exception at the _mapper.Map line as described above. The Assert happens inside AutoMapper.

[lbargaoanu]

But that means you have a dynamic map. That doesn't make any sense. Maybe you do have a map and it's not found?

[Baune8D]

@lbargaoanu I would really like to isolate the problem but it works perfectly fine in my development machine but crashes when moving the exact same source files to another machine.

[Baune8D]

@lbargaoanu I have a map setup like this

CreateMap<ConversationDto, Conversation>();

[lbargaoanu]

I think this is better suited for StackOverflow. Get back to us if the problem is with AM itself, but it doesn't look that way to me.

[Baune8D]

@lbargaoanu I have a remote debugger attached to the other faulting server and i can see it has loaded all the mapping profiles.

Is there anything you can think off that could help me debug this problem? The error is thrown inside AutoMapper itself. I am using the exact same published source code on both machines, i am running them in the same ASPNETCORE_ENVIRONMENT and against the same database. But the error only happens on that one machine.

You say that it should only run Assert if it tries to use a dynamic map? That is a clue i can go aftern.
Do you have any other clues off the top of your head?

[lbargaoanu]

Check the execution plan.

[Baune8D]

@lbargaoanu I just fetched an executionplan from both the working machine and the non-working machine.

The working machine:

(source, mapperDestination, context) => (source == null)
    ? (mapperDestination == null) ? null : mapperDestination
    : {
        try
        {
            return ObjectToEquivalencyExpressionByEquivalencyExistingMapper.Map(source, EquivalentExpression<ConversationDto, Conversation>);
        }
        catch (Exception ex)
        {
            throw new AutoMapperMappingException("Error mapping types.", ex, AutoMapper.TypePair);

            return null;
        }
    }

The non-working machine:

(src, dest, ctxt) =>
{
    Expression<Func<Conversation, bool>> typeMapDestination;
    return (src == null)
        ? null
        : {
            ctxt.ValidateMap(TypeMap);
            typeMapDestination = dest ?? 
            {
                throw ArgumentException;

                return null;
            };

            return typeMapDestination;
        };
}

Obviously something is different?

[lbargaoanu]

Yes, and that's a dynamic map, as the exception says. How is that supposed to work, I have no idea :) If you set CreateMissingTypeMaps to false, it will tell you you're missing a map.

[Baune8D]

@lbargaoanu I just wanted to let you know that i resolved the problem and you were right, it was not an AutoMapper error.

AutoMapper instantiated a version of my DbContext with a wrong connection string which made AutoMapper not able to access the DbContext on the faulting server.

The error happend here:
https://github.com/AutoMapper/AutoMapper.Collection/blob/master/src/AutoMapper.Collection.EntityFramework/GenerateEntityFrameworkPrimaryKeyPropertyMatches.cs#L24
as _context.ObjectContext threw an exception because of the wrong connection string.

Maybe a check for an invalid context could be made here and a relevant error message shown. It was extremely difficult to track down this error in the current state.

[lbargaoanu]

Yes, but the thing is, this repo is for the core package only. So really you know a lot more than me about all those extra packages you use :) I'm not saying it's easy to isolate the issue, but it's kind of your job to do it. The people responsible for those higher level packages might be able to help too.

[Baune8D]

@lbargaoanu Oh yeah forgot that this is the AutoMapper repo. I will put up an issue in AutoMapper.Collection instead about handling of the error :)

Thanks for all your help anyways, very appreciated :)

[lbargaoanu]

:)

[lock]

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