Replace default/existing services by custom implementations

[tobyee]

Sometimes, I want to replace the implement for specific interface，but it seems that IocManager.Register only register the implemented class for the first register call.
Anyway I finally found a way to do that.

// first register
IocManager.Register<IFoo, FooImpl1>();
IocManager.Resolve<IFoo>(); // == FooImpl1
// try to replace
IocManager.Register<IFoo, FooImpl2>();
IocManager.Resolve<IFoo>(); // == FooImpl1
// try another way to replace
IocManager.IocContainer.Register(Component
    .For<IFoo>()
    .ImplementedBy<FooImpl2>()
    .IsDefault());
IocManager.Resolve<IFoo>(); // == FooImpl2

But, it's not convenient.
Can IIconManager provide some method like Replace<>?

[hikalkan]

Registrations are done in module's Initialize. You can register in PreInitialize to override it. But I will consider to add some 'replace' logic to simplify it.
Thanks.

[tobyee]

+1
Happy to heart that，something like here:
https://github.com/aspnetboilerplate/aspnetboilerplate/blob/master/src/Abp.Web.Api/WebApi/AbpWebApiModule.cs#L73-L76

[hikalkan]

Hi,

I added ReplaceService method to startup configuration. For example, we can use such a code to replace IConnectionStringResolver with our custom implementation DbPerTenantConnectionStringResolver:

Configuration.ReplaceService(typeof(IConnectionStringResolver), () =>
{
    IocManager.Register<IConnectionStringResolver, DbPerTenantConnectionStringResolver>(DependencyLifeStyle.Transient);
});

We should write this in PreInitialize event of our module.

Same service can be replaced/overrided multiple times. Last one will be valid. If Module B depends on Module A and both overrides same service, then the one overrided by module B will be valid sinde Modul B's PreInitialize runs after Module A.

I made second parameter an action, instead of simply a type. Because, there may be complex replace scenarios. Example:

Configuration.ReplaceService(typeof(IConnectionStringResolver), () =>
{
    IocManager.IocContainer.Register(
        Component.For<IConnectionStringResolver, IDbPerTenantConnectionStringResolver>()
            .ImplementedBy<DbPerTenantConnectionStringResolver>()
            .LifestyleTransient()
        );
});

This is a real code from module zero that replaces IConnectionStringResolver (https://github.com/aspnetboilerplate/module-zero/blob/master/src/Abp.Zero.EntityFramework/Zero/EntityFramework/AbpZeroEntityFrameworkModule.cs#L18). Notice that it registers DbPerTenantConnectionStringResolver for two interfaces (IConnectionStringResolver, IDbPerTenantConnectionStringResolver). Also, you may need to use more advanced methods of Castle Windsor here.

[natiki]

When you update the doco could we also have an example to replace the ILogger interface with say a Serilog.ILogger for instance? ;-)

[hikalkan]

Replacing ILogger is a bit different. Because, it's registered before ABP initialized. But it's already registered in template, in global.asax file. You can just remove and register serilog. I did write it before (you can search for it).

[hikalkan]

I added shortcut extension methods. Example:

Configuration.ReplaceService<IServiceType, MyImplementation>(DependencyLifeStyle.Transient);

[brunobertechini]

Hello @hikalkan

I've reached a situation where I create a custom module with a custom configuration. I would like to allow applications using my custom module to be able to set some property and only if this property is true, I will replace the service.

Since App depends on MyCustomModule, I can't rely on PreInitialize to use ReplaceService.

AppModule1 - depends on MyCustomModule
AppModule1 configure a given setting:

public override void PreInitialize()
{
    Configuration.Modules.MyCustomModule().SettingAEnabled = true;
}

CustomModule should use this setting in order to replace a service. This is not working since it is located at Initialize rather than PreInitialize.

public override void Initialize()
{
    if(Configuration.Modules.MyCustomModule().SettingAEnabled)
    {
           Configuration.ReplaceService(typeof(IAbpSession), () =>
                {
                    IocManager.Register<IAbpSession, MyCustomModuleSession>();
                });
    }
}

Any thoughts?

Should I use other approach ?

I would like to replace IAbpSession for example if a dependant module enable specific setting.

Thanks a lot

[hikalkan]

There is a possibility to configure MyCustomModule by AppModule1 before PreInitialize. Please check this: http://www.aspnetboilerplate.com/Pages/Documents/Module-System#DocCustomModule

You can inject MyCustomModule into AppModule1's constructor and set a boolean property of it in the constructor.