.NET builders usually have to 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 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 consequence to an
Entitykind. - Can not return a posh kind in response to a
JOINcommand. - Make create, replace, and delete operations unavailable.
We will 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 couple of easy changes can overcome EF Core’s constraints.
A Hypothetical Saved Process With a Advanced Consequence
Let’s take into account GetEmployeesWithDepartment, a saved process that returns a posh consequence containing data from two associated database tables, Worker and Division:
The Worker desk references itself by means of a international 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) : Staff(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, corresponding 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 take a look at 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 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 Consequence 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 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 consequence 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 record. With the consequence 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 consequence mannequin into our utility’s EF Core DbContext file. EF gives a chic method to extending an utility’s information mannequin. Such an extension is supported with partial lessons and—particularly—by utilizing an OnModelCreatingPartial technique. To maintain EF Core’s scaffolding instruments from modifying our customized code, we’ll add our consequence 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 modifications 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 main key, if one is current.
Step 3: Specify the Key of the Mannequin
We’ll point out whether or not our SP’s consequence set has a key worth by configuring our mannequin in an OnModelCreatingPartial technique in our EFCoreSPContext definition.
If our consequence set has a key worth, we use the HasKey technique 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 technique 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 information.
Calling Advanced Saved Procedures: Straightforward As 1-2-3
To simplify calling our SP, we’ll add yet one more 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 posh kind consequence set, and our code is full. Returning to our instance question, we will use a easy command to return the division and different information 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 staff of the Toptal Engineering Weblog extends its gratitude to Alexander Skogorev for reviewing the technical content material and code samples offered on this article.
