Working with SQL views in Entity Framework Core
In Entity Framework Core 2.1 we can use Query Types as Yuriy N suggested.
A more detailed article on how to use them can be found here
The most straight forward approach according to the article's examples would be:
1.We have for example the following entity Models to manage publications
public class Magazine
{
public int MagazineId { get; set; }
public string Name { get; set; }
public string Publisher { get; set; }
public List<Article> Articles { get; set; }
}
public class Article
{
public int ArticleId { get; set; }
public string Title { get; set; }
public int MagazineId { get; set; }
public DateTime PublishDate { get; set; }
public Author Author { get; set; }
public int AuthorId { get; set; }
}
public class Author
{
public int AuthorId { get; set; }
public string Name { get; set; }
public List<Article> Articles { get; set; }
}
2.We have a view called AuthorArticleCounts, defined to return the name and number of articles an author has written
SELECT
a.AuthorName,
Count(r.ArticleId) as ArticleCount
from Authors a
JOIN Articles r on r.AuthorId = a.AuthorId
GROUP BY a.AuthorName
3.We go and create a model to be used for the View
public class AuthorArticleCount
{
public string AuthorName { get; private set; }
public int ArticleCount { get; private set; }
}
4.We create after that a DbQuery property in my DbContext to consume the view results inside the Model
public DbQuery<AuthorArticleCount> AuthorArticleCounts{get;set;}
4.1. You might need to override OnModelCreating() and set up the View especially if you have different view name than your Class.
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Query<AuthorArticleCount>().ToView("AuthorArticleCount");
}
5.Finally we can easily get the results of the View like this.
var results=_context.AuthorArticleCounts.ToList();
UPDATE According to ssougnez's comment
It's worth noting that DbQuery won't be/is not supported anymore in EF Core 3.0. See here
Views are not currently supported by Entity Framework Core. See https://github.com/aspnet/EntityFramework/issues/827.
That said, you can trick EF into using a view by mapping your entity to the view as if it were a table. This approach comes with limitations. e.g. you can't use migrations, you need to manually specific a key for EF to use, and some queries may not work correctly. To get around this last part, you can write SQL queries by hand
context.Images.FromSql("SELECT * FROM dbo.ImageView")
Here is a new way to work with SQL views in EF Core: Query Types.
The EF Core doesn't create DBset for the SQL views automatically in the context calss, we can add them manually as below.
public partial class LocalDBContext : DbContext
{
public LocalDBContext(DbContextOptions<LocalDBContext> options) : base(options)
{
}
public virtual DbSet<YourView> YourView { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<YourView>(entity => {
entity.HasKey(e => e.ID);
entity.ToTable("YourView");
entity.Property(e => e.Name).HasMaxLength(50);
});
}
}
The sample view is defined as below with few properties
using System;
using System.Collections.Generic;
namespace Project.Entities
{
public partial class YourView
{
public string Name { get; set; }
public int ID { get; set; }
}
}
After adding a class for the view and DB set in the context class, you are good to use the view object through your context object in the controller.