Structuremap, constructor that takes a list of plugins

.net, c#, structuremap

Solution

When you want all concrete instances of a type to be injected, you MUST declare the parameter as an array. You can fix your problem by changing your constructor to:

public WriterMerger(IWriter[] writers)

Be aware that code cleanup tools like ReSharper may highlight the array in your constructor and suggest you replace it with IEnumerable, if that is all that is required by your WriterMerger. However, these tools are not aware of StructureMap's requirement to use an array, so you have to ignore it.

You may also be interested in knowing that you can automatically register all of your IWriters, instead of explicitly listing them. Just change your container configuration to:

StructureMap.ObjectFactory.Initialize(x =>
{
    x.Scan(scan =>
    {
        scan.TheCallingAssembly();
        scan.AddAllTypesOf<IWriter>();
    });
});

There are a number of different options for scanning that allow you to scan different assemblies, exclude certain types, etc.

Problem

I got an interface like this ``` public interface IWriter { ... } ``` and a class ``` public class WriterMerger { public WriterMerger(IEnumerable<IWriter> writers) ... } ``` I want structuremap to fill out the constructor argument on WriterMerger with all registered IWriter's. I registered the different writers with ``` StructureMap.ObjectFactory.Initialize(x => { x.ForRequestedType<IWriter>().AddConcreteType<MemoryWriter>(); x.ForRequestedType<IWriter>().AddConcreteType<FlatFileWriter>(); x.ForRequestedType<IWriter>().AddConcreteType<DbWriter>(); } ``` however calling ``` ObjectFactory.CreateInstance<WriterMerger>(); ``` Returns an exception "No Default Instance defined for PluginFamily System.Collections.Generic.IEnumerable`1[[IWriter..]]" (class name edited) Any trick for doing this automatically? or will i have to make a custom factory method?

Original source