removed unnecessary classes

CompiledPropertyAccessor.cs

using System;
using System.Linq.Expressions;
using System.Reflection;
using WebApi.Delta;

namespace Hst.Deals.API.Infrastructure
{
    internal class CompiledPropertyAccessor<TEntityType> : PropertyAccessor<TEntityType> where TEntityType : class
    {
        private Action<TEntityType, object> _setter;
        private Func<TEntityType, object> _getter;

        public CompiledPropertyAccessor(PropertyInfo property)
            : base(property)
        {
            _setter = MakeSetter(Property);
            _getter = MakeGetter(Property);
        }

        public override object GetValue(TEntityType entity)
        {
            if (entity == null)
            {
                throw new ArgumentNullException("entity");
            }
            return _getter(entity);
        }

        public override void SetValue(TEntityType entity, object value)
        {
            if (entity == null)
            {
                throw new ArgumentNullException("entity");
            }

            _setter(entity, value);
        }

        private static Action<TEntityType, object> MakeSetter(PropertyInfo property)
        {
            Type type = typeof(TEntityType);
            ParameterExpression entityParameter = Expression.Parameter(type);
            ParameterExpression objectParameter = Expression.Parameter(typeof(Object));
            MemberExpression toProperty = Expression.Property(Expression.TypeAs(entityParameter, property.DeclaringType), property);
            UnaryExpression fromValue = Expression.Convert(objectParameter, property.PropertyType);
            BinaryExpression assignment = Expression.Assign(toProperty, fromValue);
            Expression<Action<TEntityType, object>> lambda = Expression.Lambda<Action<TEntityType, object>>(assignment, entityParameter, objectParameter);
            return lambda.Compile();
        }

        private static Func<TEntityType, object> MakeGetter(PropertyInfo property)
        {
            Type type = typeof(TEntityType);
            ParameterExpression entityParameter = Expression.Parameter(type);
            MemberExpression fromProperty = Expression.Property(Expression.TypeAs(entityParameter, property.DeclaringType), property);
            UnaryExpression convert = Expression.Convert(fromProperty, typeof(Object));
            Expression<Func<TEntityType, object>> lambda = Expression.Lambda<Func<TEntityType, object>>(convert, entityParameter);
            return lambda.Compile();
        }
    }
}

Delta.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Dynamic;
using System.Linq;
using System.Reflection;
using Hst.Deals.API.Infrastructure;

//adapted from https://github.com/ASP-NET-MVC/aspnetwebstack/tree/master/src/System.Web.Http.OData/OData

namespace WebApi.Delta.Models
{
    /// <summary>
    /// A class the tracks changes (i.e. the Delta) for a particular <typeparamref name="TEntityType"/>.
    /// </summary>
    /// <typeparam name="TEntityType">TEntityType is the base type of entity this delta tracks changes for.</typeparam>
    [NonValidatingParameterBinding]
    public class Delta<TEntityType> : DynamicObject where TEntityType : class
    {
        // cache property accessors for this type and all its derived types.
        private static ConcurrentDictionary<Type, Dictionary<string, PropertyAccessor<TEntityType>>> _propertyCache = new ConcurrentDictionary<Type, Dictionary<string, PropertyAccessor<TEntityType>>>();

        private Dictionary<string, PropertyAccessor<TEntityType>> _propertiesThatExist;
        private HashSet<string> _changedProperties;
        private TEntityType _entity;
        private Type _entityType;

        /// <summary>
        /// Initializes a new instance of <see cref="Delta{TEntityType}"/>.
        /// </summary>
        public Delta()
            : this(typeof(TEntityType))
        {
        }

        /// <summary>
        /// Initializes a new instance of <see cref="Delta{TEntityType}"/>.
        /// </summary>
        /// <param name="entityType">The derived entity type for which the changes would be tracked.
        /// <paramref name="entityType"/> should be assignable to instances of <typeparamref name="TEntityType"/>.</param>
        public Delta(Type entityType)
        {
            Initialize(entityType);
        }

        /// <summary>
        /// The actual type of the entity for which the changes are tracked.
        /// </summary>
        public Type EntityType
        {
            get
            {
                return _entityType;
            }
        }

        /// <summary>
        /// Clears the Delta and resets the underlying Entity.
        /// </summary>
        public void Clear()
        {
            Initialize(_entityType);
        }

        /// <summary>
        /// Attempts to set the Property called <paramref name="name"/> to the <paramref name="value"/> specified.
        /// <remarks>
        /// Only properties that exist on <see cref="EntityType"/> can be set.
        /// If there is a type mismatch the request will fail.
        /// </remarks>
        /// </summary>
        /// <param name="name">The name of the Property</param>
        /// <param name="value">The new value of the Property</param>
        /// <returns>True if successful</returns>
        public bool TrySetPropertyValue(string name, object value)
        {
            if (name == null)
            {
                throw new ArgumentNullException("name");
            }

            if (!_propertiesThatExist.ContainsKey(name))
            {
                return false;
            }

            PropertyAccessor<TEntityType> cacheHit = _propertiesThatExist[name];
            var isGuid = cacheHit.Property.PropertyType == typeof(Guid) && value is string;
            var isInt32 = cacheHit.Property.PropertyType == typeof(int) && value is Int64 && (long)value <= int.MaxValue;

            if (value == null && !IsNullable(cacheHit.Property.PropertyType))
            {
                return false;
            }

            if (value != null && !cacheHit.Property.PropertyType.IsPrimitive && !isGuid && !cacheHit.Property.PropertyType.IsAssignableFrom(value.GetType()))
            {
                return false;
            }

            //.Setter.Invoke(_entity, new object[] { value });
            if (isGuid) value = new Guid((string)value);
            if (isInt32) value = (int)(long)value;

            cacheHit.SetValue(_entity, value);
            _changedProperties.Add(name);
            return true;
        }

        /// <summary>
        /// Attempts to get the value of the Property called <paramref name="name"/> from the underlying Entity.
        /// <remarks>
        /// Only properties that exist on <see cref="EntityType"/> can be retrieved.
        /// Both modified and unmodified properties can be retrieved.
        /// </remarks>
        /// </summary>
        /// <param name="name">The name of the Property</param>
        /// <param name="value">The value of the Property</param>
        /// <returns>True if the Property was found</returns>
        public bool TryGetPropertyValue(string name, out object value)
        {
            if (name == null)
            {
                throw new ArgumentNullException("name");
            }

            if (_propertiesThatExist.ContainsKey(name))
            {
                PropertyAccessor<TEntityType> cacheHit = _propertiesThatExist[name];
                value = cacheHit.GetValue(_entity);
                return true;
            }
            else
            {
                value = null;
                return false;
            }
        }

        /// <summary>
        /// Attempts to get the <see cref="Type"/> of the Property called <paramref name="name"/> from the underlying Entity.
        /// <remarks>
        /// Only properties that exist on <see cref="EntityType"/> can be retrieved.
        /// Both modified and unmodified properties can be retrieved.
        /// </remarks>
        /// </summary>
        /// <param name="name">The name of the Property</param>
        /// <param name="type">The type of the Property</param>
        /// <returns>Returns <c>true</c> if the Property was found and <c>false</c> if not.</returns>
        public bool TryGetPropertyType(string name, out Type type)
        {
            if (name == null)
            {
                throw new ArgumentNullException("name");
            }

            PropertyAccessor<TEntityType> value;
            if (_propertiesThatExist.TryGetValue(name, out value))
            {
                type = value.Property.PropertyType;
                return true;
            }
            else
            {
                type = null;
                return false;
            }
        }

        /// <summary>
        /// Overrides the DynamicObject TrySetMember method, so that only the properties
        /// of <see cref="EntityType"/> can be set.
        /// </summary>
        public override bool TrySetMember(SetMemberBinder binder, object value)
        {
            if (binder == null)
            {
                throw new ArgumentNullException("binder");
            }

            return TrySetPropertyValue(binder.Name, value);
        }

        /// <summary>
        /// Overrides the DynamicObject TryGetMember method, so that only the properties
        /// of <see cref="EntityType"/> can be got.
        /// </summary>
        public override bool TryGetMember(GetMemberBinder binder, out object result)
        {
            if (binder == null)
            {
                throw new ArgumentNullException("binder");
            }

            return TryGetPropertyValue(binder.Name, out result);
        }

        /// <summary>
        /// Returns the <see cref="EntityType"/> instance
        /// that holds all the changes (and original values) being tracked by this Delta.
        /// </summary>
        [SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate", Justification = "Not appropriate to be a property")]
        public TEntityType GetEntity()
        {
            return _entity;
        }

        /// <summary>
        /// Returns the Properties that have been modified through this Delta as an 
        /// enumeration of Property Names 
        /// </summary>
        public IEnumerable<string> GetChangedPropertyNames()
        {
            return _changedProperties;
        }

        /// <summary>
        /// Returns the Properties that have not been modified through this Delta as an 
        /// enumeration of Property Names 
        /// </summary>
        public IEnumerable<string> GetUnchangedPropertyNames()
        {
            return _propertiesThatExist.Keys.Except(GetChangedPropertyNames());
        }

        /// <summary>
        /// Copies the changed property values from the underlying entity (accessible via <see cref="GetEntity()" />) 
        /// to the <paramref name="original"/> entity.
        /// </summary>
        /// <param name="original">The entity to be updated.</param>
        public void CopyChangedValues(TEntityType original)
        {
            if (original == null)
            {
                throw new ArgumentNullException("original");
            }

            if (!_entityType.IsAssignableFrom(original.GetType()))
            {
                throw new ArgumentException("Delta type mismatch", "original");
            }

            PropertyAccessor<TEntityType>[] propertiesToCopy = GetChangedPropertyNames().Select(s => _propertiesThatExist[s]).ToArray();
            foreach (PropertyAccessor<TEntityType> propertyToCopy in propertiesToCopy)
            {
                propertyToCopy.Copy(_entity, original);
            }
        }

        /// <summary>
        /// Copies the unchanged property values from the underlying entity (accessible via <see cref="GetEntity()" />) 
        /// to the <paramref name="original"/> entity.
        /// </summary>
        /// <param name="original">The entity to be updated.</param>
        public void CopyUnchangedValues(TEntityType original)
        {
            if (original == null)
            {
                throw new ArgumentNullException("original");
            }

            if (!_entityType.IsAssignableFrom(original.GetType()))
            {
                //throw Error.Argument("original", SRResources.DeltaTypeMismatch, _entityType, original.GetType());
                throw new ArgumentException("Delta type mismatch", "original");
            }

            PropertyAccessor<TEntityType>[] propertiesToCopy = GetUnchangedPropertyNames().Select(s => _propertiesThatExist[s]).ToArray();
            foreach (PropertyAccessor<TEntityType> propertyToCopy in propertiesToCopy)
            {
                propertyToCopy.Copy(_entity, original);
            }
        }

        /// <summary>
        /// Overwrites the <paramref name="original"/> entity with the changes tracked by this Delta.
        /// <remarks>The semantics of this operation are equivalent to a HTTP PATCH operation, hence the name.</remarks>
        /// </summary>
        /// <param name="original">The entity to be updated.</param>
        public void Patch(TEntityType original)
        {
            CopyChangedValues(original);
        }

        /// <summary>
        /// Overwrites the <paramref name="original"/> entity with the values stored in this Delta.
        /// <remarks>The semantics of this operation are equivalent to a HTTP PUT operation, hence the name.</remarks>
        /// </summary>
        /// <param name="original">The entity to be updated.</param>
        public void Put(TEntityType original)
        {
            CopyChangedValues(original);
            CopyUnchangedValues(original);
        }

        private void Initialize(Type entityType)
        {
            if (entityType == null)
            {
                throw new ArgumentNullException("entityType");
            }

            if (!typeof(TEntityType).IsAssignableFrom(entityType))
            {
                //throw Error.InvalidOperation(SRResources.DeltaEntityTypeNotAssignable, entityType, typeof(TEntityType));
                throw new InvalidOperationException("Delta Entity Type Not Assignable");
            }

            _entity = Activator.CreateInstance(entityType) as TEntityType;
            _changedProperties = new HashSet<string>();
            _entityType = entityType;
            _propertiesThatExist = InitializePropertiesThatExist();
        }

        private Dictionary<string, PropertyAccessor<TEntityType>> InitializePropertiesThatExist()
        {
            return _propertyCache.GetOrAdd(
                _entityType,
                (backingType) => backingType
                    .GetProperties()
                    .Where(p => p.GetSetMethod() != null && p.GetGetMethod() != null)
                    .Select<PropertyInfo, PropertyAccessor<TEntityType>>(p => new CompiledPropertyAccessor<TEntityType>(p))
                    .ToDictionary(p => p.Property.Name));
        }

        public static bool IsNullable(Type type)
        {
            return !type.IsValueType || Nullable.GetUnderlyingType(type) != null;
        }
    }
}

NonValidatingParameterBindingAttribute.cs

using System.Collections.Generic;
using System.Net.Http.Formatting;
using System.Web.Http;
using System.Web.Http.Controllers;

namespace WebApi.Delta
{
    internal sealed class NonValidatingParameterBindingAttribute : ParameterBindingAttribute
    {
        public override HttpParameterBinding GetBinding(HttpParameterDescriptor parameter)
        {
            IEnumerable<MediaTypeFormatter> formatters = parameter.Configuration.Formatters;

            return new NonValidatingParameterBinding(parameter, formatters);
        }

        private sealed class NonValidatingParameterBinding : PerRequestParameterBinding
        {
            public NonValidatingParameterBinding(HttpParameterDescriptor descriptor,
                                                 IEnumerable<MediaTypeFormatter> formatters)
                : base(descriptor, formatters)
            {
            }

            protected override HttpParameterBinding CreateInnerBinding(IEnumerable<MediaTypeFormatter> perRequestFormatters)
            {
                return Descriptor.BindWithFormatter(perRequestFormatters, bodyModelValidator: null);
            }
        }
    }
}

PerRequestParameterBinding.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Data.Linq;
using System.Diagnostics.CodeAnalysis;
using System.Diagnostics.Contracts;
using System.Globalization;
using System.Net.Http.Formatting;
using System.Threading;
using System.Threading.Tasks;
using System.Web.Http.Controllers;
using System.Web.Http.Metadata;
using System.Web.Http.ModelBinding;
using System.Web.Http.ValueProviders;
using System.Xml.Linq;

namespace WebApi.Delta
{
    internal class PerRequestParameterBinding : HttpParameterBinding
    {
        private IEnumerable<MediaTypeFormatter> _formatters;

        public PerRequestParameterBinding(HttpParameterDescriptor descriptor,
                                          IEnumerable<MediaTypeFormatter> formatters)
            : base(descriptor)
        {
            if (formatters == null)
            {
                throw new ArgumentNullException("formatters");
            }

            _formatters = formatters;
        }

        public override Task ExecuteBindingAsync(ModelMetadataProvider metadataProvider, HttpActionContext actionContext,
                                                 CancellationToken cancellationToken)
        {
            List<MediaTypeFormatter> perRequestFormatters = new List<MediaTypeFormatter>();

            foreach (MediaTypeFormatter formatter in _formatters)
            {
                MediaTypeFormatter perRequestFormatter =
                    formatter.GetPerRequestFormatterInstance(Descriptor.ParameterType, actionContext.Request,
                                                             actionContext.Request.Content.Headers.ContentType);
                perRequestFormatters.Add(perRequestFormatter);
            }

            HttpParameterBinding innerBinding = CreateInnerBinding(perRequestFormatters);
            Contract.Assert(innerBinding != null);

            return innerBinding.ExecuteBindingAsync(metadataProvider, actionContext, cancellationToken);
        }

        protected virtual HttpParameterBinding CreateInnerBinding(IEnumerable<MediaTypeFormatter> perRequestFormatters)
        {
            return Descriptor.BindWithFormatter(perRequestFormatters);
        }
    }
}

PropertyAccessor.cs

using System;
using System.Reflection;

namespace WebApi.Delta
{
    internal abstract class PropertyAccessor<TEntityType> where TEntityType : class
    {
        protected PropertyAccessor(PropertyInfo property)
        {
            if (property == null)
            {
                throw new ArgumentNullException("property");
            }
            Property = property;
            if (Property.GetGetMethod() == null || Property.GetSetMethod() == null)
            {
                throw new ArgumentException("Property Must Have Public Getter And Setter", "property");
            }
        }

        public PropertyInfo Property
        {
            get;
            private set;
        }

        public void Copy(TEntityType from, TEntityType to)
        {
            if (from == null)
            {
                throw new ArgumentNullException("from");
            }
            if (to == null)
            {
                throw new ArgumentNullException("to");
            }
            SetValue(to, GetValue(from));
        }

        public abstract object GetValue(TEntityType entity);

        public abstract void SetValue(TEntityType entity, object value);
    }
}

Add following snippet to Delta.cs to support parse enum:

// enum type
if (value != null && cacheHit.Property.PropertyType.IsEnum)
{
    try
    {
        value = Enum.Parse(cacheHit.Property.PropertyType, value.ToString(), true);
    }
    catch (ArgumentException)
    {
        // value is not a member of enum
        return false;
    }
}

Dont forget to install Microsoft.AspNet.WebApi.Core. Its relied on by these classes.

Do

dotnet add package Microsoft.AspNet.WebApi.Core