WithKeyAttribute Class |
Note: This API is now obsolete.
Namespace: Autofac.Extras.AttributeMetadata
The WithKeyAttribute type exposes the following members.
Name | Description | |
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WithKeyAttribute |
Initializes a new instance of the WithKeyAttribute class.
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Name | Description | |
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Key |
Gets the key the dependency is expected to have to satisfy the parameter.
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TypeId | When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.) |
Name | Description | |
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Equals | Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.) | |
Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) | |
GetHashCode | Returns the hash code for this instance. (Inherited from Attribute.) | |
GetType | Gets the Type of the current instance. (Inherited from Object.) | |
IsDefaultAttribute | When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.) | |
Match | When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.) | |
MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) | |
ResolveParameter |
Resolves a constructor parameter based on keyed service requirements.
(Overrides ParameterFilterAttributeResolveParameter(ParameterInfo, IComponentContext).) | |
ToString | Returns a string that represents the current object. (Inherited from Object.) |
Name | Description | |
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_AttributeGetIDsOfNames | Maps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.) | |
_AttributeGetTypeInfo | Retrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.) | |
_AttributeGetTypeInfoCount | Retrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.) | |
_AttributeInvoke | Provides access to properties and methods exposed by an object. (Inherited from Attribute.) |
This attribute allows constructor dependencies to be resolved by key. By marking your dependencies with this attribute and associating an attribute filter with your type registration, you can be selective about which service registration should be used to provide the dependency.
A simple example might be registration of a specific logger type to be used by a class. If many loggers are registered with their own key, the consumer can simply specify the key filter as an attribute to the constructor parameter.
public class Manager { public Manager([WithKey("Manager")] ILogger logger) { // ... } }
The same thing can be done for enumerable:
public class SolutionExplorer { public SolutionExplorer( [WithKey("Solution")] IEnumerable<IAdapter> adapters, [WithKey("Solution")] ILogger logger) { this.Adapters = adapters.ToList(); this.Logger = logger; } }
When registering your components, the associated key on the dependencies will be used. Be sure to specify the WithAttributeFilterTLimit, TReflectionActivatorData, TRegistrationStyle(IRegistrationBuilderTLimit, TReflectionActivatorData, TRegistrationStyle) extension on the type with the filtered constructor parameters.
var builder = new ContainerBuilder(); builder.RegisterModule(new AttributedMetadataModule()); // Register the components getting filtered with keys builder.RegisterType<ConsoleLogger>().Keyed<ILogger>("Solution"); builder.RegisterType<FileLogger>().Keyed<ILogger>("Other"); // Attach the filtering behavior to the component with the constructor builder.RegisterType<SolutionExplorer>().WithAttributeFilter(); var container = builder.Build(); // The resolved instance will have the appropriate services in place var explorer = container.Resolve<SolutionExplorer>();