Unity 3: The type does not have an accessible constructor - inversion-of-control

Question

I have a following interface and implementation
namespace ProjectName.Web
{
public interface IWebUtil
{
}
}
namespace ProjectName.Web
{
public class WebUtil : IWebUtil
{
}
}
in my config i have this registration. I am using Unity 3.
<unity xmlns="http://schemas.microsoft.com/practices/2010/unity">
<assembly name="ProjectName.Web" />
...
<register name="WebUtil" type="ProjectName.Web.IWebUtil" mapTo="ProjectName.Web.WebUtil">
<lifetime type="transient" />
</register>
...
When I try to resolve this configuration I am getting this error:
Exception is: InvalidOperationException - The type IWebUtil does not have an accessible constructor.
-----------------------------------------------
At the time of the exception, the container was:
Resolving ProjectName.Web.IWebUtil,(none)
I have tried to add empty public constructor but no sucess.
Can anybody help with this? thanks.

Answer 1

The first step is to ensure that you are loading the Unity configuration since this is not done by default. To do this:
using Microsoft.Practices.Unity.Configuration;
container.LoadConfiguration();
I'm assuming you've done this. I'm also going to assume that you are trying to resolve IWebUtil using the following code:
container.Resolve<IWebUtil>();
This throws an InvalidOperationException because IWebUtil is configured as a named registration (with name "WebUtil"). So either resolve using the configured name:
container.Resolve<IWebUtil>("WebUtil");
Or change the registration to be a default (unnamed) registration:
<register name="" type="ProjectName.Web.IWebUtil" mapTo="ProjectName.Web.WebUtil">
<lifetime type="transient" />
</register>