How to create an Instance of an Object in StructureMap Dynamically?

Question

I have an Abstract Class called "ImportRunner".

I have an implementation of the class called "ScorecardRunner".

How can I at runtime get an instance of a class such as ScorecardRunner, when I am pulling the Object Type back as a String from an XML File and it could be any implementation of ImportRunner?

My current code is as follows.

var importer = container.GetInstance<ImportRunner>();

When I try to do something like below I get a compile error.

var importer = container.GetInstance<Type.GetType("Importer.ScorecardRunner")>();

Operator '<' cannot be applied to operands of type 'method group' and 'Type'

Thanks, Tom

Answer 1

Instead of spreading your logic for creating an instance based on runtime values and shoehorning it into your StructureMap's registry, a better approach would be to simply create a factory that's responsible for determining the correct runner instance and inject that.

For example:

public class XmlReader
{
    public bool IsScoreCard { get; set; }
}

public abstract class ImportRunner
{
}

public class ScorecardRunner : ImportRunner
{
}

public class DefaultRunner : ImportRunner
{
}

public class RunnerFactory
{
    private readonly XmlReader _reader;

    public RunnerFactory(XmlReader reader)
    {
        _reader = reader;
    }

    public ImportRunner Resolve()
    {
        if (_reader.IsScoreCard)
            return new ScorecardRunner();

        return new DefaultRunner();
    }
}

Then configure it like so in your registry:

this.For<ImportRunner>().Use(ctx => ctx.GetInstance<RunnerFactory>().Resolve());