JsonConverter based on type

GenericTypeResolver.cs

// SkyClip
// - GenericTypeResolver.cs
// --------------------------------------------------------------------
// Author: Jeff Hansen <jeff@jeffijoe.com>
// Copyright (C) Jeff Hansen 2015. All rights reserved.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

namespace SkyClip.Common.Misc
{
    /// <summary>
    /// Class that can resolve a type based on input of another type.
    /// </summary>
    /// <typeparam name="TKey">
    /// The type of the key.
    /// </typeparam>
    public class GenericTypeResolver<TKey>
    {
        #region Fields

        /// <summary>
        ///     The assemblies.
        /// </summary>
        private readonly Assembly[] assemblies;

        /// <summary>
        ///     The cache.
        /// </summary>
        private readonly Dictionary<TKey, Type> cache;

        /// <summary>
        ///     The format string.
        /// </summary>
        private readonly string formatString;

        /// <summary>
        ///     The locker.
        /// </summary>
        private readonly object locker = new object();

        #endregion

        #region Constructors and Destructors

        /// <summary>
        /// Initializes a new instance of the <see cref="GenericTypeResolver{TKey}"/> class.
        /// </summary>
        /// <param name="formatString">
        /// The format string used when concatting the given key to resolve the type.
        /// </param>
        /// <param name="typesInAssembliesToBeSearched">
        /// Types in assemblies to be searched. If null or empty, the assembly
        ///     containing the type of the <see cref="TKey"/> is used.
        /// </param>
        public GenericTypeResolver(string formatString = "{0}", params Type[] typesInAssembliesToBeSearched)
        {
            this.formatString = formatString;
            if (typesInAssembliesToBeSearched == null || typesInAssembliesToBeSearched.Length == 0)
            {
                this.assemblies = new[]
                {
                    typeof(TKey).GetTypeInfo().Assembly
                };
            }
            else
            {
                this.assemblies = typesInAssembliesToBeSearched.Select(x => x.GetTypeInfo().Assembly).ToArray();
            }

            this.cache = new Dictionary<TKey, Type>();
        }

        #endregion

        #region Public Methods and Operators

        /// <summary>
        /// Resolves the specified key.
        /// </summary>
        /// <param name="key">
        /// The key.
        /// </param>
        /// <returns>
        /// The resolved type, or <c>null</c> if not found.
        /// </returns>
        public Type Resolve(TKey key)
        {
            Type type;
            if (this.cache.TryGetValue(key, out type))
            {
                return type;
            }

            lock (this.locker)
            {
                if (this.cache.TryGetValue(key, out type))
                {
                    return type;
                }

                var str = string.Format(this.formatString, key);
                var firstOrDefault = (from asm in this.assemblies
                                      from t in asm.DefinedTypes
                                      where t.Name == str
                                      select t).FirstOrDefault();
                if (firstOrDefault == null)
                {
                    return null;
                }

                type = firstOrDefault.AsType();
                this.cache.Add(key, type);
                return type;
            }
        }

        #endregion
    }
}

TypeResolutionBasedConverter.cs

// SkyClip
// - TypeResolutionBasedConverter.cs
// --------------------------------------------------------------------
// Author: Jeff Hansen <jeff@jeffijoe.com>
// Copyright (C) Jeff Hansen 2015. All rights reserved.

using System;

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

using SkyClip.Common.Misc;

namespace SkyClip.Common.Converters.Base
{
    /// <summary>
    /// Type resolution based converter. Uses a <see cref="GenericTypeResolver{TKey}"/> to resolve the type.
    /// </summary>
    /// <typeparam name="TTypeKey">
    /// The type of the type key.
    /// </typeparam>
    public abstract class TypeResolutionBasedConverter<TTypeKey> : JsonConverter
    {
        #region Fields

        /// <summary>
        ///     The resolver.
        /// </summary>
        private readonly GenericTypeResolver<TTypeKey> resolver;

        #endregion

        #region Constructors and Destructors

        /// <summary>
        /// Initializes a new instance of the <see cref="TypeResolutionBasedConverter{TTypeKey}"/> class.
        /// </summary>
        /// <param name="formatString">
        /// The format string.
        /// </param>
        /// <param name="typesInAssembliesToBeSearched">
        /// The types in assemblies to be searched.
        /// </param>
        protected TypeResolutionBasedConverter(string formatString = "{0}", params Type[] typesInAssembliesToBeSearched)
        {
            this.resolver = new GenericTypeResolver<TTypeKey>(formatString, typesInAssembliesToBeSearched);
        }

        #endregion

        #region Public Properties

        /// <summary>
        ///     Gets a value indicating whether this <see cref="T:Newtonsoft.Json.JsonConverter" /> can write JSON.
        /// </summary>
        /// <value>
        ///     <c>true</c> if this <see cref="T:Newtonsoft.Json.JsonConverter" /> can write JSON; otherwise, <c>false</c>.
        /// </value>
        public override bool CanWrite
        {
            get
            {
                return false;
            }
        }

        #endregion

        #region Public Methods and Operators

        /// <summary>
        /// Reads the JSON representation of the object.
        /// </summary>
        /// <param name="reader">
        /// The <see cref="T:Newtonsoft.Json.JsonReader"/> to read from.
        /// </param>
        /// <param name="objectType">
        /// Type of the object.
        /// </param>
        /// <param name="existingValue">
        /// The existing value of object being read.
        /// </param>
        /// <param name="serializer">
        /// The calling serializer.
        /// </param>
        /// <returns>
        /// The object value.
        /// </returns>
        public override object ReadJson(
            JsonReader reader, 
            Type objectType, 
            object existingValue, 
            JsonSerializer serializer)
        {
            var jsonObject = JObject.Load(reader);
            var key = this.ParseKey(jsonObject);
            var clipClrType = this.resolver.Resolve(key);
            var target = Activator.CreateInstance(clipClrType);
            serializer.Populate(jsonObject.CreateReader(), target);
            return target;
        }

        /// <summary>
        /// Writes the JSON representation of the object.
        /// </summary>
        /// <param name="writer">
        /// The <see cref="T:Newtonsoft.Json.JsonWriter"/> to write to.
        /// </param>
        /// <param name="value">
        /// The value.
        /// </param>
        /// <param name="serializer">
        /// The calling serializer.
        /// </param>
        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
        }

        #endregion

        #region Methods

        /// <summary>
        /// Parses the key used for type resolution from the json object.
        /// </summary>
        /// <param name="jsonObject">
        /// The json object.
        /// </param>
        /// <returns>
        /// The key.
        /// </returns>
        protected abstract TTypeKey ParseKey(JObject jsonObject);

        #endregion
    }
}

UsageExample.cs

// SkyClip
// - EventMessageJsonConverter.cs
// --------------------------------------------------------------------
// Author: Jeff Hansen <jeff@jeffijoe.com>
// Copyright (C) Jeff Hansen 2015. All rights reserved.

using System;
using System.Reflection;

using Newtonsoft.Json.Linq;

using SkyClip.Common.Converters.Base;
using SkyClip.Common.Dtos.EventMessages;

namespace SkyClip.Common.Converters
{
    /// <summary>
    ///     Event Message JSON Converter.
    /// </summary>
    public class EventMessageJsonConverter : TypeResolutionBasedConverter<string>
    {
        #region Constructors and Destructors

        /// <summary>
        ///     Initializes a new instance of the <see cref="EventMessageJsonConverter" /> class.
        /// </summary>
        public EventMessageJsonConverter()
            : base("{0}", typeof(EventMessage))
        {
        }

        #endregion

        #region Public Methods and Operators

        /// <summary>
        /// Determines whether this instance can convert the specified object type.
        /// </summary>
        /// <param name="objectType">
        /// Type of the object.
        /// </param>
        /// <returns>
        /// <c>true</c> if this instance can convert the specified object type; otherwise, <c>false</c>.
        /// </returns>
        public override bool CanConvert(Type objectType)
        {
            return typeof(EventMessage).GetTypeInfo().IsAssignableFrom(objectType.GetTypeInfo());
        }

        #endregion

        #region Methods

        /// <summary>
        /// Parses the key used for type resolution from the json object.
        /// </summary>
        /// <param name="jsonObject">
        /// The json object.
        /// </param>
        /// <returns>
        /// The key.
        /// </returns>
        protected override string ParseKey(JObject jsonObject)
        {
            return jsonObject.Value<string>("messageType");
        }

        #endregion
    }
}