Automapper Aftermap “method not found” exception

Jun Kim

When you tried to add AutoMapper to IOC container or ASP .NET Service, you may or not encounter following error. Mostly not. 

[MissingMethodException: Method not found: 'Void AutoMapper.IMappingExpression`2.ConvertUsing(System.Func`2<!0,!1>)'.]
   Abp.AutoMapper.AbpAutoMapperModule.CreateCoreMappings(IMapperConfigurationExpression configuration) +0
   Abp.AutoMapper.AbpAutoMapperModule.<CreateMappings>b__6_0(IMapperConfigurationExpression configuration) +138
   AutoMapper.MapperConfiguration.Build(Action`1 configure) +38
   AutoMapper.Mapper.Initialize(Action`1 config) +26
   Abp.AutoMapper.AbpAutoMapperModule.CreateMappings() +164
   Abp.AutoMapper.AbpAutoMapperModule.PostInitialize() +5
   Abp.Modules.<>c.<StartModules>b__15_2(AbpModuleInfo module) +13
   System.Collections.Generic.List`1.ForEach(Action`1 action) +85
   Abp.Modules.AbpModuleManager.StartModules() +281
   Abp.AbpBootstrapper.Initialize() +267
   Abp.Web.AbpWebApplication`1.Application_Start(Object sender, EventArgs e) +53
   GDPRun.Web.MvcApplication.Application_Start(Object sender, EventArgs e) in D:\WorkSpaces\App.Web\Global.asax.cs:16

When I had this, I spent so much time on googling.

This was my case
I was refactoring code and added AutoMapper to the solution.
Main Project target framework was .NET Core 3.1 and other project one was .NET CORE 2.2.
I tried to match the version between AutoMapper and AutoMapper.Extensions.Microsoft.DependencyInjection.
I installed both version 8.0.
Unit test and everything passed but it failed when I tried to run the application.

Solution.

I realized it’s mismatched version problem.
I didn’t check the dependencies as below.

After I downgraded to 6.0 of AutoMapper.Extensions.Microsoft.DependencyInjection, finally it was working.

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