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Changing Configuration at Runtime Edit on GitHub


If you need to add or change configuration to an existing StructureMap Container object, you can use the IContainer.Configure() method to add or change your container at runtime as shown below:


[Fact]
public void change_default_in_an_existing_container()
{
    var container = new Container(x => { x.For<IFoo>().Use<AFoo>(); });

    container.GetInstance<IFoo>().ShouldBeOfType<AFoo>();

    // Now, change the container configuration
    container.Configure(x => x.For<IFoo>().Use<BFoo>());

    // The default of IFoo is now different
    container.GetInstance<IFoo>().ShouldBeOfType<BFoo>();

    // or use the Inject method that's just syntactical
    // sugar for replacing the default of one type at a time

    container.Inject<IFoo>(new CFoo());

    container.GetInstance<IFoo>().ShouldBeOfType<CFoo>();
}


Best Practices

First off, the best advice on this functionality is don't use it outside of testing scenarios on the root container. The Configure() method has to use a threading lock around the internal object model of a StructureMap container and can cause serious contention at runtime if you try to override services in the main application controller. Some frameworks (looking at you NancyFx) have abused this functionality quite badly in the past and the result was not pretty.

  • Do favor writing configuration to StructureMap Registry objects, then applying that Registry to a container rather than repeatedly calling Configure()
  • Do not call Configure() on the main application container after the initial configuration. Use nested or child containers that are not shared across threads or HTTP requests if you need to override services at runtime
  • There's a potential performance hit from using Configure() at runtime because StructureMap has to recycle its internal Build Plan's based on the potential new configuration.