StructureMap treats simple types like strings, numbers of any kind, enumerations, and dates as primitive types that are completely exempt from auto wiring -- meaning that any constructor or setter dependencies on these types must be supplied as inline dependencies.

To make this concrete, if you ask StructureMap to build a concrete type that has dependencies on simple types without like this example, StructureMap will throw an exception telling you that it cannot build the instance:

public class GuyWithNoDefaultName
{
    // StructureMap will not use any kind of auto-wiring
    // on name
    public GuyWithNoDefaultName(string name)
    {
    }
}

[Fact]
public void cannot_build_simple_arguments()
{
    var container = new Container();

    Exception<StructureMapBuildPlanException>.ShouldBeThrownBy(() =>
    {
        container.GetInstance<GuyWithNoDefaultName>();
    });
}

Part of the exception message thrown in the unit test shown above is the erroneous build plan showing you that the name parameter has to be defined:

	new GuyWithNoDefaultName(String name)
	  ┗ String name = Required primitive dependency is not explicitly defined

We can build GuyWithNoDefaultName by supplying a value for name as I did in the following sample:

[Fact]
public void can_build_with_explicit_argument()
{
    var container = new Container(_ =>
    {
        _.ForConcreteType<GuyWithNoDefaultName>()
            .Configure.Ctor<string>("name").Is("Steve Winwood");
    });

    container.GetInstance<GuyWithNoDefaultName>()
        .ShouldNotBeNull();
}

See Construction Policies for an example of using a constructor policy to set a dependency on a "connectionString" argument in a conventional way.

Default Values

As a new feature in the 4.0 release, StructureMap can finally take advantage of default parameter arguments to derive the values for a primitive argument (or setter value) while still allowing you to explicitly define that parameter or setter value:

// I was listening to Jim Croce's "I've got a Name" song
// when I wrote this feature;)
public class GuyWithName
{
    public GuyWithName(string name = "Jim Croce")
    {
        Name = name;
    }

    public string Name { get; set; }
}

[Fact]
public void uses_the_default_value_if_one_exists()
{
    var container = new Container();

    // Should happily build with the default
    // value of 'name'
    container.GetInstance<GuyWithName>()
        .Name.ShouldBe("Jim Croce");
}

[Fact]
public void uses_the_default_value_if_one_exists_2()
{
    var container = new Container(_ =>
    {
        _.ForConcreteType<GuyWithName>();
    });

    // Should happily build with the default
    // value of 'name'
    container.GetInstance<GuyWithName>()
        .Name.ShouldBe("Jim Croce");
}

[Fact]
public void use_explicit_dependency_if_one_exists()
{
    var container = new Container(_ =>
    {
        _.ForConcreteType<GuyWithName>()
            .Configure.Ctor<string>("name").Is("Eric Clapton");
    });

    container.GetInstance<GuyWithName>()
        .Name.ShouldBe("Eric Clapton");
}