是否可以将结构绑定到 Unity 中的接口？

Question

I want configure Unity to resolve an interface, say ITest , to a struct, say struct Test . So far I have next:

<unity>
    <containers>
        <container>
            <types>
                <type
                    type="my.ITest, asm" 
                    mapTo="my.Test, asm">
                </type>
            </types>
        </container>
    </containers>
</unity>

but I'm getting next error:

Resolution of the dependency failed, type = "my.ITest", name = "(none)".
Exception occurred while: while resolving.
Exception is: InvalidOperationException - The type Test cannot be constructed. You must configure the container to supply this value.
At the time of the exception, the container was:    
Resolving my.Test,(none) (mapped from my.ITest,(none))

Why?

Answer 1

The problem is that you are trying to use Unity to construct a struct; because a struct is a value type, Activator.CreateInstance is going to blow chunks when trying to create it (because of the interface).

For example:

 var item = Activator.CreateInstance<Test>();

Would throw an exception "Cannot create an instance of an interface". Internally, Unity is probably using Activator.CreateInstance somewhere down the chain (I've been looking through Unity's code plex for a little while now), and that's where it will die.

I'd suggest changing to a class implementation instead of a struct.

Answer 2

Unity supports only binding of classes.