C# Dependency Injection with StructureMap

Question

We've been using StructureMap for Dependency Injection in our ASP.Net MvC 3 web apps with C#, but today I'm unable to inject a needed type into a C# CustomResolver I've built.

Here is the code in our StructureMapInitialization.cs file:

namespace UI.DependencyResolution
{
/// <summary>
/// Class Structure Map IOC intialization
/// </summary>
public static class StructureMapIocInitialization
{
    /// <summary>
    /// Initialize Method for Structure Map IOC Initialization
    /// </summary>
    /// <returns>an IContainer for Services and Repository</returns>
    public static IContainer Initialize()
    {
        ObjectFactory.Initialize(cfg =>
        {
            cfg.Scan(scan =>
            {
                scan.Assembly("Infrastructure");
                scan.Assembly("Core");
                scan.WithDefaultConventions();
                scan.ConnectImplementationsToTypesClosing(typeof(IAlertGenerator<>));
                scan.ConnectImplementationsToTypesClosing(typeof(IValidationRule<>));
            });

            cfg.For<IFilterProvider>().Use<StructureMapFilterProvider>();
            cfg.For<IControllerActivator>().Use<StructureMapControllerActivator>();

            cfg.SetAllProperties(c =>
            {
                c.WithAnyTypeFromNamespaceContainingType<ICustomerRepository>();
                c.WithAnyTypeFromNamespaceContainingType<IMachineRepository>();
                c.WithAnyTypeFromNamespaceContainingType<ICurrentUserService>();
                c.WithAnyTypeFromNamespaceContainingType<ICircuitRegistrationRepository>();
                c.WithAnyTypeFromNamespaceContainingType<IWorkflowRequestInformationRepository>();
                c.WithAnyTypeFromNamespaceContainingType<IEnumerable<IAlertGenerator<Customer>>>();

            });

        });

        return ObjectFactory.Container;
    }
}

}

And here is a snippet of the code from our AutoMapperProfile.cs file:

Mapper.CreateMap<AbstractOrganization, DashboardDetails>()
    .ForMember(dashboard => dashboard.AlertsDictionary,
    member => member.ResolveUsing<OrganizationAlertResolver>()
    .ConstructedBy(() => new OrganizationAlertResolver(
        ObjectFactory.GetInstance<ICustomerRepository>(), ObjectFactory.GetInstance<IEnumerable<IAlertGenerator<Customer>>>())));

And here is my CustomResolver code:

namespace UI.Models.CustomResolvers
{
    public class OrganizationAlertResolver : ValueResolver<Organization, Dictionary<string,   string>>
    {
        private readonly ICustomerRepository _customerRepository;

        /// <summary>
        /// Storage for customer alert generator.
        /// </summary>
        private readonly IEnumerable<IAlertGenerator<Customer>> _customerAlertGenerators;


        public OrganizationAlertResolver(ICustomerRepository customerRepository, 
            IEnumerable<IAlertGenerator<Customer>> customerAlertGenerators)
        {
            _customerRepository = customerRepository;
            _customerAlertGenerators = customerAlertGenerators;
        }

        protected override Dictionary<string,string> ResolveCore(Organization organization)
        {
            var customers = _customerRepository.GetActiveCustomersByOrgNumber(organization.OrgNumber);
            foreach (var generator in _customerAlertGenerators)
            {
                generator.PopulateAlerts(customers);
            }

        Dictionary<string, string> alertsDictionary = new Dictionary<string, string>();

            foreach (var customer in customers)
            {
                foreach (var alert in customer.Alerts)
                {
                    if(alertsDictionary.ContainsKey(alert.ToString()))
                    {
                        alertsDictionary[alert.ToString()] = alert.Message;
                    }
                    else
                    {
                        alertsDictionary.Add(alert.ToString(), alert.Message);
                    }
                }
            }
            return alertsDictionary;
        }
    }
}

So, I'm trying to use StructureMap to inject the IEnumerable of IAlertGenerator of type Customer into my CustomResolver, but I get a StructureMap 202 Exception saying that there was no default instance of that type found, even though I created the instance of it in the last entry in the StructureMap initialization file.

Here is a copy of the error message I'm getting when I run it:

StructureMap Exception Code: 202 No Default Instance defined for PluginFamily System.Collections.Generic.IEnumerable1[[Core.Domain.Alerts.IAlertGenerator1[[Core.Domain.Model.Customer, Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089

Can anyone help with suggestions on how to fix this problem?

Answer 1

In addition to what Mike has pointed out this issue can be caused by multiple instances closing the type. Based on your code:

ObjectFactory.GetInstance<IEnumerable<IAlertGenerator<Customer>>>()

I'm guessing that is what is happening.

It should be as simple as changing the above to:

ObjectFactory.GetAllInstances<IAlertGenerator<Customer>>()

which will find all instances which close IAlertGenerator<Customer>.

Answer 2

I'm not 100% certain what's going on here but I've seen two different issues in StructureMap when getting this error. The first is that the class being instantiated needs a parameterless constructor, so Customer may not have one.

The second is that even though a parameterless constructor exists, StructureMap tries to use the most fully-qualified constructor, and I've seen that with classes like SqlConnection. Below is an example of how to work around that.

x.ForRequestedType<IDbConnection>()
    .CacheBy(InstanceScope.Singleton)
    .TheDefault.Is.ConstructedBy(ctor => new SqlConnection("connection string"));

Note that I had to use the .TheDefault.Is.ConstructedBy construct to get it to use the right constructor. Before resorting to this I had tried to just pass the parameter using the .Ctor construct but just couldn't get it to work.

I hope this helps point you in the right direction.