Provide a nicer way to populate calculated properties

src/Our.Umbraco.Ditto/Attributes/DittoConversionHandlerAttribute.cs

@@ -0,0 +1,19 @@
+using System;
+using Our.Umbraco.Ditto.ComponentModel.ConversionHandlers;
+
+namespace Our.Umbraco.Ditto.Attributes
+{
+    [AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = true)]
+    public class DittoConversionHandlerAttribute : Attribute
+    {
+        public Type HandlerType { get; private set; }
+
+        public DittoConversionHandlerAttribute(Type handlerType)
+        {
+            if (!typeof(DittoConversionHandler).IsAssignableFrom(handlerType))
+                throw new ArgumentException("Handler type must inherit from DittoConversionHandler", "handlerType");
+
+            HandlerType = handlerType;
+        }
+    }
+}

src/Our.Umbraco.Ditto/Attributes/DittoOnConvertedAttribute.cs

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+using System;
+
+namespace Our.Umbraco.Ditto.Attributes
+{
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
+    public class DittoOnConvertedAttribute : Attribute
+    { }
+}

src/Our.Umbraco.Ditto/Attributes/DittoOnConvertingAttribute.cs

@@ -0,0 +1,8 @@
+using System;
+
+namespace Our.Umbraco.Ditto.Attributes
+{
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
+    public class DittoOnConvertingAttribute : Attribute 
+    { }
+}

src/Our.Umbraco.Ditto/ComponentModel/ConversionHandlers/DittoConversionHandler.cs

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+using System;
+using Umbraco.Core.Models;
+
+namespace Our.Umbraco.Ditto.ComponentModel.ConversionHandlers
+{
+    public abstract class DittoConversionHandler
+    {
+        public IPublishedContent Content { get; private set; }
+        public Type ModelType { get; private set; }
+        public object Model { get; private set; }
+
+        protected DittoConversionHandler(DittoConversionHandlerContext ctx)
+        {
+            Content = ctx.Content;
+            ModelType = ctx.ModelType;
+            Model = ctx.Model;
+        }
+
+        public virtual void OnConverting()
+        { }
+
+        public virtual void OnConverted()
+        { }
+    }
+
+    public abstract class DittoConversionHandler<TConvertedType> : DittoConversionHandler
+        where TConvertedType : class
+    {
+        public new TConvertedType Model { get; private set; }
+
+        protected DittoConversionHandler(DittoConversionHandlerContext ctx)
+            : base(ctx)
+        {
+            Model = ctx.Model as TConvertedType;
+        }
+    }
+}

src/Our.Umbraco.Ditto/ComponentModel/DittoConversionHandlerContext.cs

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+using System;
+using Umbraco.Core.Models;
+
+namespace Our.Umbraco.Ditto.ComponentModel
+{
+    /// <summary>
+    /// Provides context for conversion events.
+    /// </summary>
+    public class DittoConversionHandlerContext
+    {
+        /// <summary>
+        /// Gets or sets the content.
+        /// </summary>
+        public IPublishedContent Content { get; set; }
+
+        /// <summary>
+        /// Gets or sets the model object.
+        /// </summary>
+        public object Model { get; set; }
+
+        /// <summary>
+        /// Gets or sets the model type.
+        /// </summary>
+        public Type ModelType { get; set; }
+    }
+}