Ninject and Activator.CreateInstance - Missing Method exceptions

Question

So, I've created a class that finds all classes in my project that implement a certain interface, generates instances of those classes then aggregates the results of a method provided from the contract of that interface.

Here is my code

    public string Parse(string src,JToken json)
    {
        var type = typeof(IReplaceTokens);
        var types = AppDomain.CurrentDomain.GetAssemblies()
            .SelectMany(s => s.GetTypes())
            .Where(t => type.IsAssignableFrom(t) && t.IsClass);

        return types.Select(tokenReplacer => Activator.CreateInstance(tokenReplacer) as IReplaceTokens)
            .Aggregate(src, (current, tokenReplacerInstance) => tokenReplacerInstance.ReplaceTokens(current, json));
    }

I'm getting MissingMethod exception methods from activator because it can't find a paramaterless constructor but the two parameters required by the constructors of these types should be injected by Ninject as they are bound.

From my NinjectModule

        Bind<IConfigReader>().To<JsonConfigReader>()
                             .InSingletonScope()
                             .WithConstructorArgument("appId", _appId)
                             .WithConstructorArgument("type", _type);

        var configReader = this.KernelInstance.GetService(typeof (IConfigReader)) as IConfigReader;
        if (configReader == null || configReader.JsonWrappedInExercise) { Bind<IJsonExtractor>().To<Pm3JsonExtractor>().InSingletonScope(); }
        else { Bind<IJsonExtractor>().To<NakedJsonExtractor>().InSingletonScope(); }

Signatures for all the Constructors Activator should be constructing

public MonthTokenReplacer(IJsonExtractor extractor, IConfigReader reader)
public DateTokenReplacer(IJsonExtractor extractor, IConfigReader reader)
public LastNameTokenReplacer(IJsonExtractor extractor, IConfigReader reader) : base(extractor, "[[LastName]]", reader.FirstNameField) { }
public TokenReplacerBase(IJsonExtractor extractor, string token,string objectKey)

Plus two others with parameterless constructors.

Any idea why this isn't working?

Answer 1

By calling Activator.CreateInstance you by pass Ninject like you do when using the new operator. You are responsible to provide any dependency yourself.

call kernel.Get(tokernReplacer) instead.