WebApi: ApiExplorer and Custom ModelBinders

Question

Most of my api routes are segmented like so:

/api/{segment}/MyEntity (i.e. "/api/SegmentA/MyEntity")

Where I've defined a ModelBinder that converts from the string to a Segment object like so:

class SegmentModelBinder : IModelBinder
{
    public bool BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext)
    {
        var value = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
        if (value == null || String.IsNullOrEmpty(value.AttemptedValue))
            return false;

        bindingContext.Model = **logic to find segment object from value.AttemptedValue**;
        return true;
    }
}

Configured as:

GlobalConfiguration.Configuration.BindParameter(typeof(Segment), new SegmentModelBinder());

So my routes end up looking like this:

public class MyEntityController : BaseController
{
    [HttpGet, Route("api/{segment}/MyEntity")]
    public IEnumerable<MyEntity> Get(Segment segment)
    {
        ...
    }
}

The problem is, I'm now attempting to generate documentation for these Api calls, and ApiExplorer is completely confused by these routes and ignores them.

How do I tell it that for these routes, when it sees a parameter of type Segment, it's really just a string from the route?

Answer 1

Switching from using a ModelBinder to TypeConverter resolved the problem:

[TypeConverter(typeof(MyEntityConverter))]
public class MyEntity
{....

-

public class MyEntityConverter : TypeConverter
{
    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
    {
        if (sourceType == typeof(string))
            return true;
        return base.CanConvertFrom(context, sourceType);
    }

    public override object ConvertFrom(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value)
    {
        var key = value as string;
        if (!String.IsNullOrEmpty(key))
            return **Find Entity**;

        return base.ConvertFrom(context, culture, value);
    }
}

Edit:

If you ever return this entity in call, you need this in there as well, otherwise the newtonsoft json serializer will serialize the class to the type name:

    public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
    {
        return false;
    }