将Entity对象复制到POCO对象，其中Entity int是POCO上的Enums

Question

I'm attempting to create a copier using Jon Skeets property copy. It works fine for all properties, but not enums. I've tried several attempts at changing the method to work for enums to little success. I was wondering if anyone else might have an idea on how to do this.

Jon Skeets original, with my alterations sectioned off with comments in the BUILDCOPIER method

calls to this are

        var result = Common.PropertyCopy<POCO>.CopyFrom(Entity);

Original Jon Skeet code

/// <summary>
/// Generic class which copies to its target type from a source
/// type specified in the Copy method. The types are specified
/// separately to take advantage of type inference on generic
/// method arguments.
/// http://www.yoda.arachsys.com/csharp/miscutil/
/// </summary>
public static class PropertyCopy<TTarget> where TTarget : class, new()
{
    /// <summary>
    /// Copies all readable properties from the source to a new instance
    /// of TTarget.
    /// </summary>
    public static TTarget CopyFrom<TSource>(TSource source) where TSource : class
    {
        return PropertyCopier<TSource>.Copy(source);
    }

    /// <summary>
    /// Static class to efficiently store the compiled delegate which can
    /// do the copying. We need a bit of work to ensure that exceptions are
    /// appropriately propagated, as the exception is generated at type initialization
    /// time, but we wish it to be thrown as an ArgumentException.
    /// </summary>
    private static class PropertyCopier<TSource> where TSource : class
    {
        private static readonly Func<TSource, TTarget> copier;
        private static readonly Exception initializationException;

        internal static TTarget Copy(TSource source)
        {
            if (initializationException != null)
            {
                throw initializationException;
            }
            if (source == null)
            {
                throw new ArgumentNullException("source");
            }
            return copier(source);
        }

        static PropertyCopier()
        {
            try
            {
                copier = BuildCopier();
                initializationException = null;
            }
            catch (Exception e)
            {
                copier = null;
                initializationException = e;
            }
        }

        private static Func<TSource, TTarget> BuildCopier()
        {
            ParameterExpression sourceParameter = Expression.Parameter(typeof(TSource), "source");
            var bindings = new List<MemberBinding>();
            foreach (PropertyInfo sourceProperty in typeof(TSource).GetProperties())
            {
                if (!sourceProperty.CanRead)
                {
                    continue;
                }
                PropertyInfo targetProperty = typeof(TTarget).GetProperty(sourceProperty.Name);
                if (targetProperty == null)
                {
                    throw new ArgumentException("Property " + sourceProperty.Name + " is not present and accessible in " + typeof(TTarget).FullName);
                }
                if (!targetProperty.CanWrite)
                {
                    throw new ArgumentException("Property " + sourceProperty.Name + " is not writable in " + typeof(TTarget).FullName);
                }

                // THIS IS FALSE FOR SOURCE(INT) TARGET ENUMS
                if (!targetProperty.PropertyType.IsAssignableFrom(sourceProperty.PropertyType))
                {
                    //ADDED FOLLOWING TO HANDLE COPY FROM INT TO ENUM
                    /////////////////////////////////////////////////////////////////////////////////////////////////////
                    // Special Case because Entities are created with property as ints, not enum types
                    if (targetProperty.PropertyType.IsEnum && (sourceProperty.PropertyType == typeof(int)))
                    {
                        var expressionparam = Expression.Parameter(sourceProperty.PropertyType);
                        // cast the entity source as the enum target
                        var cast = Expression.Convert(expressionparam, targetProperty.PropertyType);
                        // add to the binding tree
                        bindings.Add(Expression.Bind(targetProperty, Expression.Property(cast, sourceProperty)));
                        continue;
                    }
                    /////////////////////////////////////////////////////////////////////////////////////////////////////

                    throw new ArgumentException("Property " + sourceProperty.Name + " has an incompatible type in " + typeof(TTarget).FullName);
                }
            Expression initializer = Expression.MemberInit(Expression.New(typeof(TTarget)), bindings);
            return Expression.Lambda<Func<TSource, TTarget>>(initializer, sourceParameter).Compile();
        }
    }
}

Enum

public enum NotificationType
{
    InAppNotificiation = 0,
    EmailNotification,
    SMS
}

Entity Class generated by EF

public class Entity
{
    public int ProcessedStatus { get; set; }
    public int Priority { get; set; }
    public System.Guid NotifyToUserId { get; set; }
    public string NotifyFrom { get; set; }
    public string NotifySubject { get; set; }
    public string NotifyMessageBody { get; set; }
    public int NotificationType { get; set; }  <-- Stored as int in DB

     public virtual MercuryUser MercuryUser { get; set; } <--complex type
}

POCO Class

public class POCO
{
    public int ProcessedStatus { get; set; }
    public int Priority { get; set; }
    public System.Guid NotifyToUserId { get; set; }
    public string NotifyFrom { get; set; }
    public string NotifySubject { get; set; }
    public string NotifyMessageBody { get; set; }
    public NotificationType NotificationType { get; set; }  <-- ENUM TYPE

    public MyUser MyUser { get; set; } <-- complex type
}

Exception thrown at the line

bindings.Add(Expression.Bind(targetProperty, Expression.Property(cast, sourceProperty)));

Property 'Int32 NotificationType' is not defined for type 'Models.Enums.NotificationType

Answer 1

So I found this post C# Using Reflection to copy base class properties and tried this instead, sometimes simple just works... not sure why this one will set the enum and also not blow up on the complex type. Perhaps its how the lambda expression interprets the object. It doesn't check the is assignable from for anything, in particular the enum type, it just sets it based on the int and property name. Kind of counter intuitive if isAssignable says NO when trying to set from a sourceproperty of type int and a targetproperty of type enum when the underlying types are the same. If anyone can shed some insight into this that would be great, for now I'm going to use the simpler method of copy listed below. Down side is it doesn't cache the copier so it has to go through it every time.

    public static T1 CopyFrom<T1, T2>(T1 obj, T2 otherObject) where T1 : class where T2 : class
    {
        PropertyInfo[] srcFields = otherObject.GetType().GetProperties(
            BindingFlags.Instance | BindingFlags.Public | BindingFlags.GetProperty);

        PropertyInfo[] destFields = obj.GetType().GetProperties(
            BindingFlags.Instance | BindingFlags.Public | BindingFlags.SetProperty);

        foreach (var property in srcFields)
        {
            var dest = destFields.FirstOrDefault(x => x.Name == property.Name);
            if (dest != null && dest.CanWrite)
                dest.SetValue(obj, property.GetValue(otherObject, null), null);
        }

        return obj;
    }