Tore.Service.ActionShell

Language: C#.

Nuget package: Tore.Service.ActionShell

Dependencies:
.net 7.0
Microsoft.AspNetCore.Mvc.NewtonsoftJson 7.0.4+

Changes in v7.0.0+:

Converted to net 7.0.

ActionShell :

A standard action filter attribute class for .Net web API

Why?

• Proven to be useful in many controller scenarios.
• This code contains the common behaviour of an action filter attribute.
• Having project dependent request scope data is so good.
• I can gather any data requied and process it and/or check sessions, access caches, databases, get the IP's etc.

In the multi tenant server mode (Kestrel default) each request arriving is processed in its own thread,
The request context is built, then the target controller instance is created.
If there are action filters:
Filter OnActionExecuting methods are called before the endpoint is invoked and,
Filter OnActionExecuted methods are called after the endpoint is left.

How?

ActionShell class as a filter :

• Constructs a developer defined object descendant of RequestScopeBase class gathering request scope data.
• Stores the scope in HttpContext.
• Before endpoint invocation, calls ActionShell.enter delegate if bound, with scope.
• After endpoint completion, calls ActionShell.leave delegate if bound, with scope.

For using it, modifications must be done before the service starts responding to requests.
For example in program.cs:

// Add this to your usings.

using Tore.Service;

Add bindings at a convenient place in the code:

      ...
      ActionShell.requestScopeType = typeof(DeveloperDefinedClassDescendingFromRequestScopeBase);
      ActionShell.enter = SomeClass.aStaticMethodToCallBeforeEnteringEndpoint;
      ActionShell.leave = SomeClass.aStaticMethodToCallAfterLeavingEndpoint;
      ...

The enter and leave methods are not mandatory.
They receive scope object which is RequestScopeBase descendant as parameter.
So if defined they should be a delegate of type:

public delegate void ActionShellDelegate(RequestScopeBase scope);

The methods should be bound as:

    ActionShell.enter = SomeClass.aStaticMethodToCallBeforeEnteringEndpoint;
    ActionShell.leave = SomeClass.aStaticMethodToCallAfterLeavingEndpoint;

Binding to controllers:

using Tore.Service; // <-- Needed.

namespace WorldDomination.Secret.Project.Controllers {

    [ApiController]
    [ActionShell] // <-- Easy.
    public class TheSuperDuperController: ControllerBase {
        // The super duper controller things here.
    }
}

RequestScopeBase :

To generate project oriented request information, developers must extend the RequestScopeBase class.
It is already populated as follows :

    routerPath = context.HttpContext.Request.Path;
    actionName = context.ActionDescriptor.RouteValues["Action"];
    modelValid = context.ModelState.IsValid;
    controller = (ControllerBase)context.Controller;
    leftAction = false;   // this is set to true at OnActionExecuted.

Here is an example, additionally collecting the IP address of the client:

public class ExampleRequestScope : RequestScopeBase {
    public string ipAddress {get; private set;} = null // We will store IP address of requester here.
    // other things needed...
    
    public ExampleRequestScope(ActionExecutingContext context):base(context){
        ipAddress = context.HttpContext.Connection.RemoteIpAddress?.ToString();
        /// collect other data needed.
    }
}

For the extended class to take control it has to be assigned like this:

    ActionShell.requestScopeType = typeof(ExampleRequestScope);

Wherever HttpContext object is accessible then scope is accessible via:

    var ctx = Somewhere.to.obtain.HttpContext;
    var scope = (ExampleRequestScope)ActionShell.fetchScope(ctx);

Note:

ActionShell assignments should be done at configuration.
  After service starts, since system goes multithreading, do not change assignments.