Introduction

A handler is an object on the producer side of a service stack. It participates in a query. It can initialize, decorate, and finalize results. Handler gets an IQuery<Request, Response> argument, which carries request and result objects, context dictionary, and service stack for futher queries.

There are five main handler interfaces. Any of which can be used for implementation.

IHandlerBase
├── IHandler<Request, Response>
├── IHandlerAsync<Request, Response>
├── IHandler
└── IHandlerAsync

Handler implements one of the four IHandler interfaces.

[Export<IHandlerBase>, Order(1000)]
public class TypeHandler : IHandler<string, Type>
{
    public void Handle(IQuery<string, Type> query)
    {
        // Already handled
        if (query.Handled()) return;
        // Find type
        Type? type = Type.GetType(query.Request);
        // No type found
        if (type == null) return;
        // Assign result
        query.Response.SetValue(type);
    }
}

All handler interfaces.

IHandlerBase
├── IHandlerBaseSync
│   ├── IHandler
│   │   └── IHandlerWithOrder
│   └── IHandlerT
│       └── IHandler<Request, Response>
│           └── IHandlerWithOrder<Request, Response>
│
├── IHandlerBaseAsync
│   ├── IHandlerAsync
│   │   └── IHandlerAsyncWithOrder
│   └── IHandlerAsyncT
│       └── IHandlerAsync<Request, Response>
│           └── IHandlerAsyncWithOrder<Request, Response>
│
├── IHandlerDecoration
│   └── IHandlerCast
└── IHandlerCastable