asp.net web api - use camel case serialization only for specific actions

Question

I've used WebAPI for a while, and generally set it to use camel case json serialization, which is now rather common and well documented everywhere.

Recently however, working on a much larger project, I came across a more specific requirement: we need to use camel case json serialization, but because of backward compatibility issues with our client scripts, I only want it to happen for specific actions, to avoid breaking other parts of the (extremely large) website.

I figure one option is to have a custom content type, but that then requires client code to specify it.

Is there any other option?

Thanks!

Answer 1

Try this:

public class CamelCasingFilterAttribute : ActionFilterAttribute
{
    private JsonMediaTypeFormatter _camelCasingFormatter = new JsonMediaTypeFormatter();

    public CamelCasingFilterAttribute()
    {
        _camelCasingFormatter.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
    }

    public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
    {
        ObjectContent content = actionExecutedContext.Response.Content as ObjectContent;
        if (content != null)
        {
            if (content.Formatter is JsonMediaTypeFormatter)
            {
                actionExecutedContext.Response.Content = new ObjectContent(content.ObjectType, content.Value, _camelCasingFormatter);
            }
        }
    }
}

Apply this [CamelCasingFilter] attribute to any action you want to camel-case. It will take any JSON response you were about to send back and convert it to use camel casing for the property names instead.