Wiring with constructors and properties
We name "wiring" the process a container uses to look up and "connect" dependencies (just like an object graph). Different than other containers, the MicroKernel always infers dependencies based on type (property type or constructor parameter type).
The MicroKernel supports both constructors and public writable properties to pass dependencies. Each constructor parameter is considered a non-optional dependency. By default the MicroKernel will never invoke a constructor specifying a null value to one of the parameters (this can be changed, though).
Properties on the component implementation are also checked. When the component is created, the collected properties are inspected and if some can have their value supplied, the container will do it. In contrast to constructors, Properties are considered optional properties.
Now imagine that you have registered two components - WoodFurnitureBuilder and IronFurnitureBuilder. Both implement the service IFurnitureBuilder. Suppose a service ILivingRoomBuilder depends on an implementation of IFurnitureBuilder. Which one will it get?
By default, the container will supply the first one that was registered for the IFurnitureBuilder. This is a rule and was set to allow the container behavior to be always predictable. In our case, WoodFurnitureBuilder was registered first. What if you want to use the IronFurnitureBuilder?
Whenever the DefaultDependencyResolver is requested to supply a service dependency, it checks the ComponentModel of the component that is requesting the dependency value. It looks on the ParameterModelCollection dictionary for an entry with the dependency name (usually the constructor parameter name or the property name). If found, then it will certainly be a dependency override which instructs the DefaultDependencyResolver to not use the default behavior, but instead use what the programmer supplied (a different component id).
The MicroKernel does not perform any check to see if the component id on the ParameterModel evaluates to a type which is compatible with the expecting type.
We will explain how to configure such overrides when talking about the Windsor Container configuration.
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