![]() Most of the time that’s a good idea because otherwise any time you accessed a School object, EF would bring back all related Pupil data regardless of whether it were needed. If you subsequently try to access data from one of the related Pupil objects, only then will it be retrieved from the database. This happens because by default, EF uses a loading strategy called Lazy Loading, where it doesn’t fetch any data associated with the virtual Pupils property on the School object when the first query is run. If we look in ANTS at what happens when this code runs, we see a query run once to get a list of schools in New York, but another query is also run 500 times to fetch Pupil information. Database accessīy far the biggest performance issues you’re likely to encounter are of course around accessing the database. – setup instructions are included in the readme. To play along at home, you can grab the code for most of these examples from There’s a database with two tables for Schools and their Pupils, and a WinForms app using an EF code-first model of this database to fetch data in a variety of inefficient ways. We’ll use examples from a simplified school management system. In this article we’ll look at where these ‘traps’ are hiding, examining how they can be spotted and what you can do about them. ![]() Unfortunately, several traps that are easy to fall into have given it a reputation for performing poorly but it doesn’t have to be this way! The performance of Entity Framework may once have been inherently poor but isn’t any more if you know where the landmines are. ![]() We’ll set up CRUD (create, read, update delete) operations for our application.Compared to writing your own SQL to access data, you can become miraculously more productive by using Entity Framework (EF). Next in part four, we’re going to get to the real meat of the operation. Once this application is built for the first time, it will populate this data into the database. This gives us data to start within our application. This is known as seeding the database, and it only happens once when it’s created. If that doesn’t show any errors, you can update the database: dotnet ef database updateĪwesome, we now have data in our database. Then run Nimbletext, and your final code should look like this:Īnd now it’s ready to run: dotnet ef migrations add SeedData This will automatically generate the C# code you need to populate this database. In the second section paste in this code: new Employee , In the top section, paste in your CSV data: You can get a copy of NimbleText free, however I highly reccomend getting the pro version. We want to do this for all 100 employees we’ve created though. Protected override void OnModelCreating(ModelBuilder modelBuilder)Īs you can see, we’re creating a new Employee to insert into the database. Open up EmployeeContext.cs and add in the following method: But I want this data to be seeded by my application. csv into SQLite, using DB Browser or the SQLite command prompt. There are two ways I can put it into the database. So now I have a nice CSV file with the mock data. I have downloaded the mock data and saved it into the Data folder of the application. I’m going to use Mockaroo for this project to create some fake employee data we can use for our application. To use this database, it needs to have some data. Now, when you open up Data\Employees.db, it should look like this: Then run the following command in the Package Manager Console: dotnet ef database update We start by opening up our Package Manager terminal and running the following commands: dotnet ef migrations add InitialCreate Entity Framework Core will scaffold our database, create the SQL necessary to create it and execute it. The initial migration is creating our database for the first time. You may want to change this for production scenarios, see. () ī(options => options.UseSqlite(connectionString)) Var builder = WebApplication.CreateBuilder(args)
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |