Entity framework Core Raw SQLQueries with custom model - asp.net-core

Question

Using Entity Framework 6, I was able to use execute a Raw SQL Query and use a custom model which was not defined in the DBContext in order to store the output of the query. A simple example is the following:
List<MyModel> data = context.Database.SqlQuery<MyModel>("SELECT Orders.OrderID, Customers.CustomerName FROM Orders INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID;").ToList();
I execute one SQL command and I expect a list of custom models.
I try to do something similar with Entity Framework Core and the closest example that I found will force me to define a property from DBContext. This will not allow me to use a custom model to fill the data that SQL server will return.
var books = context.Books.FromSql("SELECT * FROM Books").ToList();
This query informs Entity Framework Core that the query will return a list of books. Is there a way to implement something like this in Entity Framework Core?

Answer 1

From .NET Core 2.1:
Add modelBuilder.Query<YourModel>() to OnModelCreating(ModelBuilder modelBuilder)
Use context.Query<YourModel>().FromSql(rawSql) to get data

Answer 2

Here's how I was able to get this working (for completeness):
MyModel.cs:
public class MyModel
{
// The columns your SQL will return
public double? A { get; set; }
public double? B { get; set; }
}
Add class that just inherits from your original EF context class (i called mine DbContextBase):
public class DbContext : DbContextBase
{
public virtual DbSet<MyModel> MyModels { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
// Necessary, since our model isnt a EF model
modelBuilder.Entity<MyModel>(entity =>
{
entity.HasNoKey();
});
}
}
Use that class (instead of your original EF context class):
// Use your new db subclass
using (var db = new DbContext())
{
var models = await db.MyModels.FromSqlRaw(...).ToListAsync(); // E.g.: "SELECT * FROM apple A JOIN banana B ON A.col = B.col"
}
Notes:
If you need to, just use FromSqlInterpolated instead of
FromSqlRaw
The "db context" subclass allows you to update EF models without affecting your "polyfill" code
Works with SQL Server stored procs that return only 1 result set

Answer 3

The question was about .NET Core 2. Now I have a solution and I am going to write it here so that someone else could use it in case he/she needs it.
First of all we add the following method in dbContext class
public List<T> ExecSQL<T>(string query)
{
using (var command = Database.GetDbConnection().CreateCommand())
{
command.CommandText = query;
command.CommandType = CommandType.Text;
Database.OpenConnection();
List<T> list = new List<T>();
using (var result = command.ExecuteReader())
{
T obj = default(T);
while (result.Read())
{
obj = Activator.CreateInstance<T>();
foreach (PropertyInfo prop in obj.GetType().GetProperties())
{
if (!object.Equals(result[prop.Name], DBNull.Value))
{
prop.SetValue(obj, result[prop.Name], null);
}
}
list.Add(obj);
}
}
Database.CloseConnection();
return list;
}
}
Now we can have the following code.
List<Customer> Customers = _context.ExecSQL<Customer>("SELECT ......");

Answer 4

follow these steps:
Create your model
Probably it could be better if you can reduce it to a model as generic as possible but it's not a must:
public class MyCustomModel
{
public string Text { get; set; }
public int Count { get; set; }
}
Add it to your own DbContext
Create DbSet for your custom model
public virtual DbSet<MyCustomModel> MyCustomModelName { get; set; }
Keep in mind to specify your custom model has no key
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
...
modelBuilder.Entity<MyCustomModel>().HasNoKey();
}
Use it from your dbContext instance
async public Task<List<MyCustomModel>> GetMyCustomData()
{
var rv = new List<MyCustomModel>();
using (var dataContext = new DbContext())
{
var sql = #"
select textField as 'Text', count(1) as 'Count'
from MyTable";
rv = await dataContext.Set<MyCustomModel>().FromSqlRaw(sql).ToListAsync();
}
return rv;
}