.NET builders usually must name a database saved process (SP) from their C# server layer. Microsoft’s Entity Framework (EF) Core can be utilized to map or import SPs as features however, sadly, EF Core doesn’t natively assist the retrieval of advanced outcomes from saved procedures. This is because of limitations in EF Core’s out-of-the-box answer that:

• Prohibit a saved process’s outcome to an Entity sort.
• Can’t return a fancy sort in response to a JOIN command.
• Make create, replace, and delete operations unavailable.

We are able to get round these restrictions by utilizing C#, .NET, Microsoft SQL Server, and EF Core collectively. This workaround can be utilized with any .NET-supported database or .NET language that helps EF Core, offered the utility code is translated into that language. We’ll have a look at an instance saved process to see how a number of easy changes can overcome EF Core’s constraints.

A Hypothetical Saved Process With a Advanced Consequence

Let’s contemplate GetEmployeesWithDepartment, a saved process that returns a fancy outcome containing data from two associated database tables, Worker and Division:

The Worker desk references itself by way of a overseas key from its ManagerId area. It additionally references the Division desk from the Worker.DepartmentId area related to the Division desk’s Id column. The ordinal relationships between these tables are:

Relationships = Worker(1) : Division(1) and Division(1) : Workers(N)

Now let’s have a look at GetEmployeesWithDepartment, an SP that returns an Worker desk row matching the enter parameter Worker.Id. Our SP returns the Id worth and all of its related data, comparable to the worker’s Division and Identify values:

CREATE OR ALTER PROCEDURE [dbo].[GetEmployeesWithDepartment] 	
    @id INT
AS
BEGIN
    SET NOCOUNT ON;

    SELECT [E].*, [D].[Name] AS [Department]
    FROM [dbo].[Employee] [E]
        INNER JOIN [dbo].[Department] [D] ON [E].[DepartmentId] = [D].[Id]
    WHERE [E].[Id] >= @id
END

Let’s say we wish to decide the division related to the primary worker listed in a easy check database (in our instance, the primary worker listed is John in Engineering). We wish to execute this SP from our C# code, so let’s configure EF Core to assist calling GetEmployeesWithDepartment as a parameterized SP.

Notice: Earlier than you proceed, scaffold your database utilizing the Scaffold-DbContext command within the Package deal Supervisor Console or the dotnet ef dbcontext scaffold command in .NET Core CLI.

Step 1: Create a Saved Process Consequence Set Mannequin

First, we’ll create a file known as GetEmployeesWithDepartment_Result.cs and outline the construction for our advanced return sort:

public class GetEmployeesWithDepartment_Result
{
    public int Id { get; set; }
    public string Identify { get; set; }
    public int DepartmentId { get; set; }
    public int? ManagerId { get; set; }
    public int Wage { get; set; }
    public decimal? Bonus { get; set; }
    public string Division { get; set; }
}

Utilizing Microsoft SQL Server because the database server, we will explicitly confirm the SP outcome column sorts by executing the sp_describe_first_result_set command:

EXEC sp_describe_first_result_set N'[dbo].[GetEmployeesWithDepartment]'

This command shows the saved process’s columns and related sort listing. With the outcome sort outlined, we transfer on to updating our EF mannequin.

Step 2: Embrace the Mannequin within the DbContext File

We’re prepared to include the outcome mannequin into our utility’s EF Core DbContext file. EF gives a sublime method to extending an utility’s knowledge mannequin. Such an extension is supported with partial courses and—particularly—by utilizing an OnModelCreatingPartial methodology. To maintain EF Core’s scaffolding instruments from modifying our customized code, we’ll add our outcome mannequin to EFCoreSPContext.SP.cs, a partial C# class:

utilizing EFCoreSP.Information.SPs;
utilizing Microsoft.EntityFrameworkCore;
utilizing System.Collections.Generic;
utilizing System.Linq;

namespace EFCoreSP.Information
{
    public partial class EFCoreSPContext : DbContext
    {
        public digital DbSet<GetEmployeesWithDepartment_Result>
            GetEmployeesWithDepartment_Results { get; set; }

        // We’ll add subsequent adjustments right here
    }
}

Right here’s how EFCoreSPContext.SP.cs seems to be in our repository. We now want so as to add code that identifies our mannequin’s major key, if one is current.

Step 3: Specify the Key of the Mannequin

We’ll point out whether or not our SP’s outcome set has a key worth by configuring our mannequin in an OnModelCreatingPartial methodology in our EFCoreSPContext definition.

If our outcome set has a key worth, we use the HasKey methodology to explicitly establish the property related to that key worth:

partial void OnModelCreatingPartial(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<GetEmployeesWithDepartment_Result>(entity => 
        entity.HasKey(e => e.Id));      
}

If our entity has no key worth, we use the HasNoKey methodology as an alternative:

partial void OnModelCreatingPartial(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<GetEmployeesWithDepartment_Result>(entity => 
        entity.HasNoKey());       
}

Our mannequin definition is now full. We’re able to name the SP and retrieve our instance worker knowledge.

Calling Advanced Saved Procedures: Simple As 1-2-3

To simplify calling our SP, we’ll add another public methodology to the EFCoreSPContext file. The strategy’s definition accepts the Worker.Id worth offered, passes that Id to the SP, and retrieves the generated advanced outcomes as a listing:

public IEnumerable<GetEmployeesWithDepartment_Result> 
    SP_GetEmployeesWithDepartment(int id)
{
    return this.GetEmployeesWithDepartment_Results
        .FromSqlInterpolated($"[dbo].[GetEmployeesWithDepartment] {id}")
        .ToArray();
}

Our DbContext file is now able to name a saved process and return a fancy sort outcome set, and our code is full. Returning to our instance question, we will use a easy command to return the division and different knowledge related to the primary worker in our database:

var staff = dbContext.SP_GetEmployeesWithDepartment(1);

We utilized a easy, but intelligent and highly effective, answer to return a non-database entity from a saved process. This method entails comparatively few strains of supporting code and yields a substantial payoff when utilizing EF Core to retrieve advanced outcomes.

The editorial workforce of the Toptal Engineering Weblog extends its gratitude to Alexander Skogorev for reviewing the technical content material and code samples introduced on this article.