Executing Advanced Entity Framework Core Saved Procedures

.NET builders typically 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 capabilities however, sadly, EF Core doesn’t natively help the retrieval of complicated outcomes from saved procedures. This is because of limitations in EF Core’s out-of-the-box resolution that:

• Prohibit a saved process’s end result to an Entity kind.
• Can not return a fancy kind in response to a JOIN command.
• Make create, replace, and delete operations unavailable.

We are able to get round these restrictions through the use of 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 couple of easy changes can overcome EF Core’s constraints.

A Hypothetical Saved Process With a Advanced End result

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

The Worker desk references itself by a international key from its ManagerId area. It additionally references the Division desk from the Worker.DepartmentId area linked 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 info, reminiscent of the worker’s Division and Title 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 want to execute this SP from our C# code, so let’s configure EF Core to help calling GetEmployeesWithDepartment as a parameterized SP.

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

Step 1: Create a Saved Process End result Set Mannequin

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

public class GetEmployeesWithDepartment_Result
{
    public int Id { get; set; }
    public string Title { 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 are able to explicitly confirm the SP end result column varieties 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 kind listing. With the end result kind outlined, we transfer on to updating our EF mannequin.

Step 2: Embody the Mannequin within the DbContext File

We’re prepared to include the end result mannequin into our software’s EF Core DbContext file. EF gives a sublime method to extending an software’s knowledge mannequin. Such an extension is supported with partial courses and—particularly—through the use of an OnModelCreatingPartial technique. To maintain EF Core’s scaffolding instruments from modifying our customized code, we’ll add our end result 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 appears to be like in our repository. We now want so as to add code that identifies our mannequin’s main key, if one is current.

Step 3: Specify the Key of the Mannequin

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

If our end result set has a key worth, we use the HasKey technique to explicitly determine 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 technique as a substitute:

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 yet another public technique to the EFCoreSPContext file. The tactic’s definition accepts the Worker.Id worth offered, passes that Id to the SP, and retrieves the generated complicated outcomes as an inventory:

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 kind end result set, and our code is full. Returning to our instance question, we are able to 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, resolution 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 complicated 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.