Just a quick pre-emptive question before we start to seriously investigate using Lucene.
Currently building a C# WPF application, using MVVM and Microsoft Entity framework. My lead has brought up the point that this might represent a problem with us not being able to let Lucene directly access the database, and therefore there might be difficulty in getting it to tie in with our BOL/DAL.
Anyone have any experience of tying Lucene in with such a model?
I have successfully used Lucene in a WPF application using MVVM, and I didn't encounter any problems.
Lucene should sit in your services layer. In the MVVM world, Lucene is your Model. The ViewModel just calls into Lucene with queuries and formats the results in whatever way is needed for the View to present it.
In my application, I had a service that was responsible for pulling relevant data out of the database and adding it to the Lucene index.
Related
I'm designing a backend app using a GraphQL, MongoDB, .Net Core stack where performance must be excellent. Wondering if given that the .net core Mongo driver supports Linq if we could just skip using a Mongoose or EFCore middle layer and just use a Repository pattern on top of the DB layer?
We're normally an EF shop so familiarity is a plus but it carries so much baggage and this app schema is fairly simple. 80% of our DB will be "sql-like" and only 20% actually requires NoSql, but due to cloud hosting costs we're going with Mongo for everything. Mongoose was suggested to me, but I'm not really seeing what I gain there.
Has anyone used this combo? Any suggestions appreciated!
Mongoose is different stack all together and there I am guessing you basically plan to use a another model to provide abstraction over the top of data that is being stored in the database.
https://docs.mongodb.com/realm/graphql/ => Check this out if GraphQL is what you are specifically looking for, without any big layer change.
One added layer in between your let's say .NET backend and an extra layer would extra hop BTW. (If you use another tech to just act as abstraction layer)
[Pre]
I have to say that I'm dummy newbie who is trying to get together important puzzles with such crucial details as DDD, TDD, MVVM, and EFCore. I have an about 10 years of windows form develop experience in complete wrong manner, and after I'm joined to Plurasight I'm understood that I'm just lost my last 10 years, and this is really sad :).
[Problem description]
I have an App that i want to re-write from scratch by using latest and greatest technics that've learned for the last 6 month on Pluralsight, but the problem is that these new knowledge’s is stopping me, because simply I'm afraid that I'll do it wrong again...(that is stupid I know, but it is what it is).
So back to my questions, I have a big problem domain, and pretty well documented business logic, which i have to turn in to the code. I'm understand that my start point is design data layer, for these purposes I want to use Entity framework core (I saw Julie Lerman's course on Pluralsight and I think's she is amazing and inspires me to use EFCore as ORM for my app). But at the same time leakage of experience produces more questions than what I’ve learned with Pluralsight, and I will try to write them all(please don’t judge me too hard)
It is looks like that I will need 2 or even more data model projects in my solution, and here is why I have multiple document set types, each of the type contain more than one reference books used to generate unique file names and data sheets. But it looks weird to me have 3 Data model projects such as MyApp.PackType1.DataModel, MyApp.PackType2.DataModel, and each of them will be preinstalled with the EFCore, and each of them will generates its own database based on Data Context defined by EF. Isn’t it very redundant or this is correct way?
I don’t understand how to join these multiple Data Models projects, including Shared Kernel into the one nice model
I don’t understand what is the best way to design my data classes? Should they be just POCO’s or I can design them as nice looking classes with the private var’s and public properties? What are the best practices in here?
Also I don’t understand what is the best practice to use a MVVM pattern on top of that, and is it applicable at all to use MVVM in this case?
Should I keep my Tests in separate projects like MyApp.PackType1.DataModel.Tests, or keep them in same project?
Best regards,
Maks!
P.S.
Apologize for unclear definitions and questions, English isn't my native language.
It's very complicated to answer your question because you have asked for a lot of details, but I going to provide a brief answer and I hope it will be helpful.
You can have only one model for your entities (DDD) and create sub model from this model in your end level projects (Web API or UI)
Read point #1
You have to create an Entity Layer project that represents your database and then you can create DTO's for specific scenarios
From my point of view, use Angular but you can use another UI framework such as React or VueJs, but I prefer to use Angular to build UI interfaces and consume .NET Core Web API from client
Create unit tests and integration tests for you Web API projects and as additional feature you can use Db in memory provider for tests
May be this guide is useful: https://www.codeproject.com/Articles/1160586/Entity-Framework-Core-for-Enterprise
Regards
Hm, multiple DbContexts (models) usually come about when you have distinct databases you are using. General rule is one Context = one Database. Exceptions can occur when there are a lot of tables that can be grouped functionally, but there are downsides to that approach.
A DbContext is a repository pattern but for individual tables. Using a Unit of Work pattern and layering with a custom repository provider would allow you to make it "appear" as a single database, hiding the complexity from the front-end.
Your entity descriptions are usually created as straight POCO. You can get creative with different DTOs
In a nutshell, an MVVM pattern goes like this:
Request from UI to a controller
Controller possibly issues multiple calls to Data Layer to gather data
Assemble data in a single ViewModel (everything the page needs)
Return to UI
The beauty of the approach is single roundtrip (request/response) to the UI
Separate Project in my opinion. There are techniques to spoof the database connection using EF so you are not using "live" data.
That CodeProject article will come in handy.
I heard that companies that use Java technologies, they used to build their own custom Framework that wraps Hibernate. However, is it really feasible for their .Net peers to do the same thing with NHibernate or Entity Framework?
This is almost always a horrible idea - I think Ayende sums it up best in this article. In general, you should consider NHibernate itself to be the "wrapper" around your data access - attempting to build an abstraction layer on top of it is probably going to be a losing proposition.
Actually, you should check out some of the articles on .NET Junkie's weblog. He wrote several great posts on how to deal with repositories, queries, commands and so on. We've been using these in a very large enterprise system where we switch between an in-memory dictionary, an in-memory SQLite database and a production environment using SQL Server or Oracle. Obviously, we use NHibernate for this.
I use the repository pattern and a separate project/dll to abstract away the data framework nhibernate / entity framework. this is a good starting point http://codebetter.com/petervanooijen/2008/04/04/wrapping-up-nhibernate-in-repositories/
Is Database class just a wrapper for ADO.NET which makes use of db simpler ? What's its limits ?
Yes - the Database Helper is a wrapper around ADO.NET. It is designed to minimize the code that a beginner needs to get started with querying databases, similar to how its done in PHP. Its limits depend on your point of view. As someone who is just starting to learn web development and databases, you might think that the helper is a stroke of genius. As a professional developer, you might not like the fact that it returns dynamic types or that it doesn't prevent people dynamically constructing their SQL and potentially opening up their application to SQL injection attacks.
HI Guys,
I was watching these videos series about Entity Framework:
http://msdn.microsoft.com/en-us/data/ff191186.aspx
is that easy building application in real world programming??? and is it ....reliable...has good performance...
"I am a graduate.."
thanks
Entity Framework is a valid real world data access tool. It is very easy to get up and running with EF. You simply import (or create in EF 4) your data model. You then can rename it to make it more code friendly. And then you are off querying databases.
Performance
I have been on multiple projects that use it, some which require high throughput, others that have low performance requirements. Entity Framework out of the box is not the fastest solution in the world, so there are a lot of performance tweaks that have to go on, but its all do able.
Reliability
We never have issues with reliability. We have never had an issue with EF in general, its always data content related. Trying to insert duplicated data, etc.
Other Tangibles
EF follows a pattern which allows for you to do some fun stuff with templates and abstract classes. All entities inerit from a class, entities that have references inherit from other classes. All Entity Contexts inherit from ;) ObjectContext classes, which provide a base set of functionality that allows you to create generic DAO implementations that can be reused throughout the enterprise.
If you are using UI dev, you can also use Data Services that wrap EF, as a fast gateway to your databse. The only downside of this is that you dont have access to the full suite of the Entity Framework.