I would like to know your opinions and advices about BaseEntity and composite key.
I found a lot example how we use BaseEntity class in EF but I am confused because all example project and explanation so sterile.
They explains the easiest part of the problem but where there is nothing about hard things.
A lot of them state that no need composite keys just identity (surrogate) keys but I feel so source code will be so idiotic that way.
I use the BaseEntity abstract class with Id and Create Data, Last Modified Date, etc. fields but where I find possibility to use neutral or composite keys I do so.
Unfortunately, it is not easy so I ask you if you know some good example sites for this problem write to me, please.
Related
I have a bunch of questions regarding Java 8 and SDN4. I created a model in Neo4j v3.0, played a bit with Cypher queries, and now moved to creating a Spring Boot application. As i started coding classes in Java, I've begun to rethink some of my model as well. Here's some questions in my mind (and I haven't found an example explaining this):
Do you need to use Interfaces in Java, with SDN?For eg. I'd code a Product interface and then have my products implement it, but is that how it's done when working with labels?
This is somewhat tied to my question on inheritance - I'd usually have a ProductFamily that my Product would inherit from. At the database level its modeled as (:Product)-[PartOf]->(:ProductFamily), but in the code these would not be super/sub class.
Any examples of using Generics in a graph context?
Is there a way to define constraints on what relationships a node can have and their direction in Java?
I understand there is probably not one right answer, but there's precious little on the web, so hope to get enlightened here!
If you had a Product interface annotated with #NodeEntity, then the you'll have the Product label in addition to the label on your implementing class, which I assume is what you want. If your interface isn't annotated, then your implementing classes will not inherit a label from it.
Not sure what you mean- if you say you have a ProductFamily that Product inherits from, but in the code it would not be a super/sub class?
Based on your graph model, if you want (:Product)-[PartOf]->(:ProductFamily) then you will have a Product class that maintains a reference to a ProductFamily class, and that reference annotated with #Relationship. If the Product class inherits from ProductFamily then persisting the Product will result in two labels- Product and ProductFamily because a Product IS-A ProductFamily.
How do you see yourself using generics- the answer really depends on that. Some cases are supported, some are not (an example of something not supported right now is equivalent of template.createRelationBetween in SDN4)
Yes, via the #Relationship annotation which accepts a type and direction. Note that this annotation only constrains your domain model, but you could very well flout this by creating relationships in another direction via a custom query.
I've been looking at the different approaches to solving the mass assignment issues with MVC as well as doing things the right way.
So far, the 2 approaches which I think are the best are below: (I have also looked at AutoMapper)
1: Value Injecter - This seems to do the job pretty well, but also relies on a third party library
2: Using the UpdateModel method and bind to a View Model interface which exposes a subset of the required properties in your domain model. http://www.codethinked.com/easy-and-safe-model-binding-in-aspnet-mvc
Before I jump in and code my whole application (without spending a week on each to find out which one I actually like) using one of the above practices, does anybody have real world experience of using these 2 methods and which one you would recommend?
in simple scenarios where you have only text fields matching strings/int properties anything will do just as well.
but when you have properties on the viewmodel that match objects in the model (FK in the DB) it gets a bit more complex, you might need to pull data from the DB for some individual props and map some property of that object to the ViewModel, stuff like that.
prodinner asp.net mvc demo application uses valueinjecter in Mapper classes, there's a pdf where this approach is explained, you can download it here: http://prodinner.codeplex.com/
General consensus from all the reading I've done on this topic is that if you're going from a Entity or Domain Model (from your database) to a View Model to show on the form feel free to use automation tools like AutoMapper or whatever your preferred tool is to automate it.
If you are however going from a Input or Form Model (the object populated via the automatic model binding) back into to your Entity or Domain Model, do not automate this. It's a slippery slope to navigate correctly and can result in your automation tool mapping over fields that were not intended/permitted. Everything I've read about this (and various implementations myself) suggest the best practice is to do this manually/explicitly. It's pretty straight forward and object initializers can make it very easy to read.
var person = new Person()
{
PersonId = model.PersonId,
FirstName = model.FirstName,
LastName= model.LastName
}
personService.UpdatePerson(person);
Something along that line.
I´ve not had much contact with Entity Framework yet and therefore I´d like to hear some guys with experience.
I´ve got an MVC project and my DataAccess lies in a different project where I want to place my EDMX file.
So how would I like to name this file? Per default it is "Model1.edmx" but in the context of MVC I don´t feel comfortable with this name. Is it really a Model?
I tend to call it "DbModel" or something to indicate that it is database related stuff.
And how do you guys call the entity class? I think I like the EF typical name "DbContext".
So within my controllers I´d have something like
public class WorldController : Controller
{
DbContext db = new DbContext();
public ActionResult Own()
{
var allContinents = db.Continents;
[...]
}
}
Sorry for being fussy but I really do care about naming.
It is good to care about naming!
How to do it depends on the composition your application. Let's say you have a web application for registering UFO sightings, to name something common. If there is a separate part of your db (maybe a separate schema) containing users, roles and permissions, you could create a context named AuthorizationContext, and for the business part a context named UfoDbContext.
I mean, if there are clear aggregates with no or little overlap you could create separate contexts for them with clear names. If one context fits the bill, I would still give it some meaningful name (not DbContext) that relates to your application domain.
There are people (I'm not one of them) that like to work with one context per application "column" (db to UI) or "user story". Meaningful names are even more important then.
My suggestion would be to use something that indicates the contents in the naming. You could take part of your project name, for instance, and bring it down into the name of the EDMX. Include something that makes it less generic.
I also tend to include an "Ef" in my naming, which I started when working on a project that already had an existing ORM.
To take Microsoft's prototypical example: if your project fell under the umbrella name of Norwind, here's how I would name some of the files in my model project:
EDMX File:
NorwindEfModel.edmx
Generator/TT File:
NorwindEfDbContext.tt
Entities class:
NorwindEntities
I can't say this is exactly how Microsoft would have it if you downloaded a sample project from them (though I believe it would be similar), but I think it's a reasonable naming structure and it fits my needs. The bottom line is this largely comes down to opinion and your need for specific distinction.
I was going to implement a custom DisplayAttribute in order to allow dynamic display values based on model values, but I can't because DisplayAttribute is sealed.
Before I go off and write my own customer attribute that emulates the behavior of DisplayAttribute, can anybody think of why this is sealed? I'm assuming there is a reason behind it, and if so, that may be the same reason I shouldn't try to "hack" around this limitation by rolling my own.
I'm not asking anyone to read Microsoft's mind, I'm just hoping someone already knows the by-design reason it's sealed, so that I can take that into account when rolling (or avoiding) my own implementation.
In general it is considered best practice to seal attributes. FxCop has a rule about it, defined here. From that page:
The .NET Framework class library provides methods for retrieving custom attributes. By default, these methods search the attribute inheritance hierarchy; for example Attribute.GetCustomAttribute searches for the specified attribute type, or any attribute type that extends the specified attribute type. Sealing the attribute eliminates the search through the inheritance hierarchy, and can improve performance.
Many of the MVC attributes (ActionFilter, etc) are unsealed because they are specifically designed to be extended, but elements in the DataAnnotations namespace are not.
Not exactly what you asked, but following your intent...
You can still allow for dynamic display values, you just wont extend the DisplayAttribute.
Instead, you can implement your own IModelMetadataProvider which could contain any logic needed to create dynamic display values.
Brad Wilson, from the ASP.NET MVC team, has a good article and sample of this on his blog: http://bradwilson.typepad.com/blog/2010/01/why-you-dont-need-modelmetadataattributes.html
I am currently using auto mapper and I think it is a good tool but I don't like how it can't handle view model to domain situations. It kinda sucks that I have to go in the automapping and map each one.
I been looking around and been reading about valueinjecter and how it can handle this. I am wondering though can it do these features what automapper has?
Can you make something like resolvers and formatters?
Can you combine values. For instance on the client side I have a datetime but it is broken into 2 different textboxes(one has a timepicker one has a datepicker). Of course in the database it is stored as one field.
So in my domain(what is later used with nhibernate) I have DateTime DateChoosen. In my view model I would have String Date, String Time.
Right now in automapper I have a resolver(or formatter I can't remember) that takes both of the view model values and converts it into a DateTime and then maps it to the domain.
Can I do something like this in valueinjecter?
I also been looking around and found this Automapper simulation with the ValueInjecter. I am wondering if this would have all the automapper features or if it just makes the syntax look like automapper.
If it actually uses automapper too, does anyone know if they keep using the most current versions?
It's a different concept, it's not the exact same thing so it doesn't have formatters and resolvers, it only has ValueInjections which are applied when injecting from one object to another
the exact scenario that you are describing is shown in prodinner sample, here:
http://code.google.com/p/prodinner/source/browse/trunk/WebUI/Mappers/DinnerMapper.cs
DinnerMapper inherits this:
http://code.google.com/p/prodinner/source/browse/trunk/WebUI/Mappers/Mapper.cs