<p>Hello, - I had previously posted this as a workitem on enterprise library codeplex: http://entlib.codeplex.com/workitem/28939 - but to outline the issue and add some more detail:-</p> <p>&nbsp;</p> <p>Unity v1.2 let you BuildUp() against an existing instance, and it would inject the dependencies into that instance (via method / property injection), even though the instances type in question did not have a public constructor. Which makes perfect sense to me, as why would unity possibly need to know about a constructor when all its doing is injecting into an existing instance all the time!</p> <p>&nbsp;</p> <p>Unity 2 throws an exception if you BuildUp() there is no public constructor. I have outlined this in the tests.</p> <p>&nbsp;</p> <p>I understand from ctavares comment on previous workitem at entlib codeplex, that when unity encounters a type it tries to find a public constructor &quot;in case&quot; you need to do a resolve() later on down the line.</p> <p>If this is correct, then call me a simpleton, but in this instance this optimisation feature of unity seems a waste of resources and a breaking change from v1.2 that will mean that I have to give all my classes public constructors, even though unity will never actually need to construct a single one. Its common to have private / internal constructors especially when your object instances are obtained through factories for example.</p> <p>&nbsp;</p> <p>I am guessing a solution here would be some mechanism by which to tell unity that for particular types, it can disable its &quot;public constructor&quot; checks as unity will never be asked to create / Resolve() an instance of that type. BuildUp() would then succeed for those types - as it will not have to check for a public constructor as it will know it will never be needed.</p> <p>&nbsp;</p> <p>Kind Regards</p> <p>Darrell</p>

    // Verify the type we're trying to build is actually constructable -
    // CLR primitive types like string and int aren't.
    private static void GuardTypeIsNonPrimitive(IBuilderContext context, SelectedConstructor selectedConstructor)
    {
        var typeToBuild = context.BuildKey.Type;
        if(!typeToBuild.IsInterface)
        {
            // MODIFCATION 13/12/2010 BEGIN
            //if(typeToBuild == typeof(string) || selectedConstructor == null)
            // MODIFCATION 13/12/2010 END
            if (typeToBuild == typeof(string))
            {
                throw new InvalidOperationException(
                    string.Format(
                        CultureInfo.CurrentCulture,
                        Resources.TypeIsNotConstructable,
                        typeToBuild.Name));
            }
        }
    }