Question

I am using Unity DI in a windows forms application. It is working so far resolving dependencies to the main form in program.cs like this:

    static void Main()
{
    IUnityContainer container = new UnityContainer();
    container.AddNewExtensionIfNotPresent<EnterpriseLibraryCoreExtension>();
    container.RegisterType<IAccountService, AccountService>();
    container.RegisterType<IAccountRepository, AccountRepository>();

    Application.EnableVisualStyles();
    Application.SetCompatibleTextRenderingDefault(false);
    Application.Run(container.Resolve <MainForm>());
}

My problem is when my MainForm tries creates a child form:

    ChildForm childForm = new ChildForm();
    childForm.Show();

I am getting an error because I’m trying to use constructor injection and I’m not passing in the constructor arguments. I also tried using setter injection with the [Dependency] attribute but that didn’t work either. How should I accomplish this? I could have my main form have all the dependencies and pass the required objects to the child forms, but if I end up having many child forms then the main form would be messy.

Answer 1

In order for Unity to inject the constructor arguments, you’ll need to use the container to resolve the child form. So you’ll need to hold a reference to your container somewhere, then call:

ChildForm childForm = container.Resolve<ChildForm>();

This will allow Unity to evaluate the ChildForm constructors and inject the appropriate dependencies.