topic Re: Dependency Injection and command classes in Revit API Forum

Dependency Injection and command classes

Anonymous — Sun, 18 Sep 2016 16:34:34 GMT

Hello. I want to use DI and IoC in my plugin. And I want to inject my dependencies in constructor. To do this, I need to get control of command class creation. Let assume we have such code in command class

    [Transaction(TransactionMode.Manual)]
    class CmdTypeToMarkSeparateType : IExternalCommand
    {
        private ISomeService _service { get; set; }
        // some service should be passed to command.
        // In fact it is constructor injection
        public CmdTypeToMarkSeparateType(ISomeService service)
        {
            _service = service;
        }
        public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
        {
            TaskDialog.Show("Test name", _service.message);
            return Result.Succeeded;
        }
    }

to make this possible, I should be able to control creation of command classes. In AutoCAD, I achieve this, by registrering all commands by myself and wrapping them in lambda, where I am extracting all constructor parameters by my self, using my DI container. How can I achieve this in Revit? Let assume, I have such code:

private void AddPushButton(RibbonPanel panel)
{
    PushButton pushButton = panel.AddItem(new PushButtonData("HelloWorld",
        "HelloWorld", @"D:\Sample\HelloWorld\bin\Debug\HelloWorld.dll", "HelloWorld.CsHelloWorld")) as PushButton;

    // Set ToolTip and contextual help
    pushButton.ToolTip = "Say Hello World";
    ContextualHelp contextHelp = new ContextualHelp(ContextualHelpType.Url,
        "http://www.autodesk.com");
    pushButton.SetContextualHelp(contextHelp);

    // Set the large image shown on button
    pushButton.LargeImage =
        new BitmapImage(new Uri(@"D:\Sample\HelloWorld\bin\Debug\39-Globe_32x32.png"));
}

As we can see we pass only classname of command class. Maybe there is a way to do something like this:

        private void AddPushButton(RibbonPanel panel, IServiceContainer services)
        {
            // Add push button without command
            PushButton pushButton = panel.AddItemSomeWay();

            pushButton.onClick = () => {
                // Create command class using my DI container and pass dependencoes
                var cmdClass = services.GetInstance<CmdTypeToMarkSeparateType>();
                // call execute method
                cmdClass.Execute();
            }
            
        }

Or maybe there is a way to override some default Revit activator, where it creates command class instances? Or maybe there is a way to pass parameters to execute method (it is the worst method), and I will get my service container directly in Execute method?

Re: Dependency Injection and command classes

Mustafa.Salaheldin — Sun, 18 Sep 2016 17:23:16 GMT

I don't know why you need to do so but try to create a static public variable/method in the external command and pass to it whatever you want the process it in the Execute method.

Re: Dependency Injection and command classes

Anonymous — Mon, 19 Sep 2016 05:59:49 GMT

I want to implement constructor dependency injection, which is considered to be good practice in c# development. I have managed to do it in AutoCad and it was really useful.

Re: Dependency Injection and command classes

Anonymous — Tue, 05 Jun 2018 09:27:58 GMT

Hi,

Did you ever get a nicer solution for this?

Re: Dependency Injection and command classes

RichWhitfield — Mon, 04 Dec 2023 22:43:36 GMT

Testability, extensibility etc...all the standard arguments for programming to an interface.

Re: Dependency Injection and command classes

Kennan.Chen — Wed, 06 Dec 2023 14:06:09 GMT

I have implemented a DI framework in my add-in. I borrowed the SimpleContainer implementation from an early version of the ASP.NET Blazor framework while I was reading through its source code. The SimpleContainer is a singleton class that provides the registration and injection. And I have a ContainerObject base class that handles the constructor injection and property injection.

Actually there was a similar reply last year in which I shared my implementation.

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