Question

I have and issue binding to my model with an action filter using reflection. The problem im having is I cannot access the sub class to set the value to a property –> FilePath (string).

Here are the goals I wanted to achive.

1) Upload images using an action filter so I dont reference the HttpContext in my controller action.

2) Force consistancy as all of my models using this method will have to inherit from a generic base abstract class BaseModel<T>.

3) Automatically bind file paths to the model entity

The generic type entity of BaseModel<T> is implementing an interface (IUpload) which will force the use of the property I want to be able to set (FilePath) for further consistancy and generics.

Here is my binding attempt within my action filter…

   private void MyCustomBindVoid(ActionExecutingContext filterContext, string filePath)
    {
        foreach (object x in filterContext.ActionParameters.Values)
        {
            Type baseType = GetGenericTypeBase(x.GetType(), typeof(BaseModel<>));

            if (baseType == null)
            {
                throw new NullReferenceException("All view models must inherit from the BaseModel abstract class.");
            }

            foreach (PropertyInfo prop in baseType.GetProperties())
            {
                Type entity = Type.GetType(prop.PropertyType.AssemblyQualifiedName, true, false);

                if (entity != null)
                {
                    foreach (Type i in entity.FindInterfaces((type, criteria) => true, null))
                    {
                        if (i == typeof(IUpload))
                        {
                            foreach (MemberInfo info in i.GetMembers())
                            {
                                PropertyInfo entityInfo = entity.GetProperty(info.Name);

                                if (entityInfo != null)
                                {
                                    entityInfo.SetValue("I_CANNOT_FIGURE_HOW_TO_GET_THE_OBJECT_TO_BIND_HERE", filePath, null);
                                    return;
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    private Type GetGenericTypeBase(Type type, Type genericType)
    {
        while (type != typeof(object))
        {
            if (type.IsGenericType && type.GetGenericTypeDefinition() == genericType)
            {
                return type;
            }

            type = type.BaseType;
        }

        return null;
    }

I know its not ideal model binding in the action filter but I have run out of ideas of passing the file path to the model.

This does seem to work and I’ve acomplished this by putting a FilePath (string) property onto the model which is inheriting from BaseModel<T> which can be accessed by the following. As the “x” object is available as a concreate instance.

foreach (MemberInfo info in i.GetMembers())
{
   PropertyInfo baseInfo = baseType.GetProperty(info.Name);

   if (baseInfo != null)
   {
      baseInfo.SetValue(x, filePath, null);
      return;
    }
 }

This again will lead to writing the same code in my controller action as i will have to manually set the FilePath property on the BaseModel<T> to the FilePath property of the entity <T>.

Any help will be very much appreciated (Even if it means a drastic rethink)

Answer 1

Found what I was looking for courtesy of http://codecallback.com/

The full explaination can be found below.

http://codecallback.com/forum/3/thread/4/asp-net-mvc-3-model-binding-to-sub-class-with-action-filter-using-reflection

All I need to do was to create an instance of the sub class like so.

PropertyInfo entityInfo = entity.GetProperty(info.Name);
if (entityInfo != null)
{
  object y = prop.GetValue(x, null); /* THIS IS THE FIX */
  entityInfo.SetValue(y, filePath, null);
  return;
}

Doing this will allow me to decorate my action with a [UploadFileAttribute(param, param)] and let all the file upload, path generation and binding to the property of the generic entity model get taken care of so all I had to do was call MyRepository.Create(Model.Entity);