C＃反射-将两个对象合并在一起

Question

I have a need to update object A's property if null with that from object B's equivalent property if that is not null. I wanted code I can use for various objects.

I had a version working until one of the objects contained a propert of type List, which is where I have a blank in the code below. My main question is how can I best implement this part of the code. Secondly is there a better way of doing this whole thing and thirdly I know its never going to be rapid but any suggestions to speed it up would be appreciated.

Thanks in advance.

public T MergeWith<T, U>(T primarySource, U secondarySource) where U : class, T
    {
        Type primaryType = typeof(T);
        Type secondaryType = typeof(U);
        foreach (PropertyInfo primaryInfo in primaryType.GetProperties())
        {
            if (primaryInfo.CanWrite)
            {
                object currentPrimary = primaryInfo.GetValue(primarySource, null);

                PropertyInfo secondaryInfo = secondaryType.GetProperty(primaryInfo.Name);
                object currentSecondary = secondaryInfo.GetValue(secondarySource, null);

                if (currentPrimary == null && currentSecondary != null)
                {
                    primaryInfo.SetValue(primarySource, currentSecondary, null);
                }
                else if ((currentPrimary != null && currentSecondary != null) && isChildClass(primaryInfo))
                {
                    if (isCollection(currentPrimary))
                    {
                        // here


                    }
                    else
                    {
                        MethodInfo method = typeof(NavigationModel).GetMethod("MergeWith");
                        MethodInfo generic = method.MakeGenericMethod(primaryInfo.PropertyType, primaryInfo.PropertyType);
                        object returnChild = generic.Invoke(this, new object[2] { currentPrimary, currentSecondary });
                    }
                }
            }
        }

        return primarySource;
    }

    private bool isCollection(object property) 
    {
        return typeof(ICollection).IsAssignableFrom(property.GetType())
            || typeof(ICollection<>).IsAssignableFrom(property.GetType()); 
    }


    private bool isChildClass(PropertyInfo propertyInfo)
    {
        return (propertyInfo.PropertyType.IsClass && !propertyInfo.PropertyType.IsValueType &&
                            !propertyInfo.PropertyType.IsPrimitive && propertyInfo.PropertyType.FullName != "System.String");
    }

Answer 1

I have created the below extension method for use in my latest project and it works fine, collections and all. It is a pretty much a simpler version of what you are doing in your method. With mine both classes have to be the same type. What problem do you encounter with collections?

    public static class ExtensionMethods
    {
        public static TEntity CopyTo<TEntity>(this TEntity OriginalEntity, TEntity NewEntity)
        {
            PropertyInfo[] oProperties = OriginalEntity.GetType().GetProperties();

            foreach (PropertyInfo CurrentProperty in oProperties.Where(p => p.CanWrite))
            {
                if (CurrentProperty.GetValue(NewEntity, null) != null)
                {
                    CurrentProperty.SetValue(OriginalEntity, CurrentProperty.GetValue(NewEntity, null), null);
                }
            }

            return OriginalEntity;
        }
    }

Answer 2

Hi I modified Ben Robinsons solution in order to not overwrite Collections or list, instead, it adds the elements of one object to the other one where the merging is happening:

 public static class ExtensionMethods
{
    public static TEntity CopyTo<TEntity>(this TEntity OriginalEntity, TEntity EntityToMergeOn)
    {
        PropertyInfo[] oProperties = OriginalEntity.GetType().GetProperties();

        foreach (PropertyInfo CurrentProperty in oProperties.Where(p => p.CanWrite))
        {
            var originalValue = CurrentProperty.GetValue(EntityToMergeOn);

            if (originalValue != null)
            {
                IListLogic<TEntity>(OriginalEntity, CurrentProperty, originalValue);
            }
            else
            {
                var value = CurrentProperty.GetValue(OriginalEntity, null);
                CurrentProperty.SetValue(EntityToMergeOn, value, null);
            }
        }

        return OriginalEntity;
    }

    private static void IListLogic<TEntity>(TEntity OriginalEntity, PropertyInfo CurrentProperty, object originalValue)
    {
        if (originalValue is IList)
        {
            var tempList = (originalValue as IList);
            var existingList = CurrentProperty.GetValue(OriginalEntity) as IList;

            foreach (var item in tempList)
            {
                existingList.Add(item);
            }

        }
    }
}