Can someone explain Microsoft Unity

Question

I ve been reading the articles on MSDN about Unity  Dependency Injection  Inversion of Control   but I think I need it explained in simple terms  or simple examples   I m familiar with the MVPC pattern  we use it here   but I just can t really grasp this Unity thing yet  and I think it s the next step in our application design

User · Answer

Unity is an IoC  The point of IoC is to abstract the wiring of dependencies between types outside of the types themselves  This has a couple of advantages  First of all  it is done centrally which means you don t have to change a lot of code when dependencies change  which may be the case for unit tests    Furthermore  if the wiring is done using configuration data instead of code  you can actually rewire the dependencies after deployment and thus change the behavior of the application without changing the code

User · Answer

I just watched the 30 minute Unity Dependency Injection IoC Screencast by David Hayden and felt that was a good explaination with examples   Here is a snippet from the show notes   The screencast shows several common usages of the Unity IoC  such as    Creating Types Not In Container  Registering and Resolving TypeMappings  Registering and Resolving Named TypeMappings  Singletons  LifetimeManagers  and the ContainerControlledLifetimeManager  Registering Existing Instances  Injecting Dependencies into Existing Instances  Populating the UnityContainer via App config   Web config  Specifying Dependencies via Injection API as opposed to Dependency Attributes  Using Nested   Parent-Child   Containers

User · Answer

I am covering most of the examples of Dependency Injection in ASP NET Web API 2  public interface IShape       string Name   get  set       public class NoShape   IShape       public string Name   get  set       I have No Shape      public class Circle   IShape       public string Name   get  set       Circle      public class Rectangle   IShape       public Rectangle string name                this Name   name             public string Name   get  set       Rectangle       In DIAutoV2Controller cs Auto Injection mechanism is used   RoutePrefix  api v2 DIAutoExample    public class DIAutoV2Controller   ApiController       private string ConstructorInjected      private string MethodInjected1      private string MethodInjected2      private string MethodInjected3        Dependency      public IShape NoShape   get  set          Dependency  Circle        public IShape ShapeCircle   get  set          Dependency  Rectangle        public IShape ShapeRectangle   get  set          Dependency  PiValueExample1        public double PiValue   get  set          InjectionConstructor      public DIAutoV2Controller  Dependency  Circle   IShape shape1   Dependency  Rectangle   IShape shape2  IShape shape3                this ConstructorInjected   shape1 Name      amp      shape2 Name      amp      shape3 Name              NonAction       InjectionMethod      public void Initialize                 this MethodInjected1    Default Initialize done               NonAction       InjectionMethod      public void Initialize2  Dependency  Circle   IShape shape1                this MethodInjected2   shape1 Name              NonAction       InjectionMethod      public void Initialize3 IShape shape1                this MethodInjected3   shape1 Name              HttpGet       Route  constructorinjection        public string constructorinjection                 return  Constructor Injected      this ConstructorInjected              HttpGet       Route  GetNoShape        public string GetNoShape                 return  Property Injected      this NoShape Name              HttpGet       Route  GetShapeCircle        public string GetShapeCircle                 return  Property Injected      this ShapeCircle Name              HttpGet       Route  GetShapeRectangle        public string GetShapeRectangle                 return  Property Injected      this ShapeRectangle Name              HttpGet       Route  GetPiValue        public string GetPiValue                 return  Property Injected      this PiValue              HttpGet       Route  MethodInjected1        public string InjectionMethod1                 return  Method Injected      this MethodInjected1              HttpGet       Route  MethodInjected2        public string InjectionMethod2                 return  Method Injected      this MethodInjected2              HttpGet       Route  MethodInjected3        public string InjectionMethod3                 return  Method Injected      this MethodInjected3            In DIV2Controller cs everything will be injected from the Dependency Configuration Resolver class   RoutePrefix  api v2 DIExample    public class DIV2Controller   ApiController       private string ConstructorInjected      private string MethodInjected1      private string MethodInjected2      public string MyPropertyName   get  set        public double PiValue1   get  set        public double PiValue2   get  set        public IShape Shape   get  set            MethodInjected      NonAction      public void Initialize                 this MethodInjected1    Default Initialize done                 MethodInjected      NonAction      public void Initialize2 string myproperty1  IShape shape1  string myproperty2  IShape shape2                this MethodInjected2   myproperty1      amp      shape1 Name      amp      myproperty2      amp      shape2 Name             public DIV2Controller string myproperty1  IShape shape1  string myproperty2  IShape shape2                this ConstructorInjected   myproperty1      amp      shape1 Name      amp      myproperty2      amp      shape2 Name              HttpGet       Route  constructorinjection        public string constructorinjection                 return  Constructor Injected      this ConstructorInjected              HttpGet       Route  PropertyInjected        public string InjectionProperty                 return  Property Injected      this MyPropertyName              HttpGet       Route  GetPiValue1        public string GetPiValue1                 return  Property Injected      this PiValue1              HttpGet       Route  GetPiValue2        public string GetPiValue2                 return  Property Injected      this PiValue2              HttpGet       Route  GetShape        public string GetShape                 return  Property Injected      this Shape Name              HttpGet       Route  MethodInjected1        public string InjectionMethod1                 return  Method Injected      this MethodInjected1              HttpGet       Route  MethodInjected2        public string InjectionMethod2                 return  Method Injected      this MethodInjected2            Configuring the Dependency Resolver  public static void Register HttpConfiguration config        var container   new UnityContainer        RegisterInterfaces container       config DependencyResolver   new UnityResolver container           Other Web API configuration not shown     private static void RegisterInterfaces UnityContainer container        var dbContext   new SchoolDbContext           Registration with constructor injection     container RegisterType lt IStudentRepository  StudentRepository gt  new InjectionConstructor dbContext        container RegisterType lt ICourseRepository  CourseRepository gt  new InjectionConstructor dbContext            Set constant default value of Pi   3 141      container RegisterInstance lt double gt   PiValueExample1   3 141       container RegisterInstance lt double gt   PiValueExample2   3 14           without a name     container RegisterInstance lt IShape gt  new NoShape             with circle name     container RegisterType lt IShape  Circle gt   Circle   new InjectionProperty  Name    I am Circle             with rectangle name     container RegisterType lt IShape  Rectangle gt   Rectangle   new InjectionConstructor  I am Rectangle             Complex type like Constructor  Property and method injection     container RegisterType lt DIV2Controller  DIV2Controller gt           new InjectionConstructor  Constructor Value1   container Resolve lt IShape gt   Circle     Constructor Value2   container Resolve lt IShape gt              new InjectionMethod  Initialize            new InjectionMethod  Initialize2    Value1   container Resolve lt IShape gt   Circle     Value2   container Resolve lt IShape gt              new InjectionProperty  MyPropertyName    Property Value            new InjectionProperty  PiValue1   container Resolve lt double gt   PiValueExample1             new InjectionProperty  Shape   container Resolve lt IShape gt   Rectangle             new InjectionProperty  PiValue2   container Resolve lt double gt   PiValueExample2

User · Answer

Unity is a library like many others that allows you to get an instance of a requested type without having to create it yourself   So given   public interface ICalculator       void Add int a  int b      public class Calculator   ICalculator       public void Add int a  int b                return a   b            You would use a library like Unity to register Calculator to be returned when the type ICalculator is requested aka IoC  Inversion of Control   this example is theoretical  not technically correct    IoCLlibrary Register lt ICalculator gt  Return lt Calculator gt       So now when you want an instance of an ICalculator you just     Calculator calc   IoCLibrary Resolve lt ICalculator gt       IoC libraries can usually be configured to either hold a singleton or create a new instance every time you resolve a type   Now let s say you have a class that relies on an ICalculator to be present you could have    public class BankingSystem       public BankingSystem ICalculator calc                 calc   calc             private ICalculator  calc      And you can setup the library to inject a object into the constructor when it s created   So DI or Dependency Injection means to inject any object another might require

User · Answer

Unity is just an IoC  container   Google StructureMap and try it out instead  A bit easier to grok  I think  when the IoC stuff is new to you    Basically  if you understand IoC then you understand that what you re doing is inverting the control for when an object gets created    Without IoC    public class MyClass      IMyService  myService       public MyClass               myService   new SomeConcreteService                 With IoC container   public class MyClass      IMyService  myService       public MyClass IMyService myService              myService   myService               Without IoC  your class that relies on the IMyService has to new-up a concrete version of the service to use  And that is bad for a number of reasons  you ve coupled your class to a specific concrete version of the IMyService  you can t unit test it easily  you can t change it easily  etc    With an IoC container you  configure  the container to resolve those dependencies for you  So with a constructor-based injection scheme  you just pass the interface to the IMyService dependency into the constructor  When you create the MyClass with your container  your container will resolve the IMyService dependency for you    Using StructureMap  configuring the container looks like this    StructureMapConfiguration ForRequestedType lt MyClass gt    TheDefaultIsConcreteType lt MyClass gt     StructureMapConfiguration ForRequestedType lt IMyService gt    TheDefaultIsConcreteType lt SomeConcreteService gt       So what you ve done is told the container   When someone requests the IMyService  give them a copy of the SomeConcreteService   And you ve also specified that when someone asks for a MyClass  they get a concrete MyClass     That s all an IoC container really does  They can do more  but that s the thrust of it - they resolve dependencies for you  so you don t have to  and you don t have to use the  new  keyword throughout your code     Final step  when you create your MyClass  you would do this    var myClass   ObjectFactory GetInstance lt MyClass gt       Hope that helps  Feel free to e-mail me

User · Answer

MSDN has a Developer s Guide to Dependency Injection Using Unity that may be useful     The Developer s Guide starts with the basics of what dependency injection is  and continues with examples of how to use Unity for dependency injection   As of the February 2014 the Developer s Guide covers Unity 3 0  which was released in April 2013

[c#] Can someone explain Microsoft Unity?

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