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Pankaj is a back-end developer and Microsoft Certified Professional with more than 18 years of experience within the Microsoft ecosystem, including C#, VB.NET, SQL Server, and cloud computing with Microsoft Azure. He has worked as a .NET developer at companies including Granicus, Gartner, and Jacobs.
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.NET developers often need to call a database stored procedure (SP) from their C# server layer. Microsoft’s 实体框架(EF)核心 可用于将sp映射或导入为函数,但是, unfortunately, EF Core doesn’t natively support the retrieval of complex results from stored procedures. This is due to limitations in EF Core’s out-of-the-box solution that:
Entity
type.JOIN
command.我们可以使用 C#, .NET, Microsoft SQL Server和EF Core合作. 此解决方案可用于任何 .. net支持的数据库或 .NET language that supports EF Core, provided the utility code is translated into that language. We’ll look at an example stored procedure to see how a few simple adjustments can overcome EF Core’s constraints.
Let's consider GetEmployeesWithDepartment
, a stored procedure that returns a complex result containing information from two related database tables, Employee
and Department
:
The Employee
表通过 foreign key from its ManagerId
field. 它还引用了 Department
table from the Employee.DepartmentId
字段连接到 Department
table’s Id
column. 这些表之间的序数关系是:
Relationships = Employee(1) : Department(1) and Department(1) : Employees(N)
Now let’s look at GetEmployeesWithDepartment
,一个返回an的SP Employee
与输入参数匹配的表行 Employee.Id
. Our SP returns the Id
value and all of its associated information, such as the employee’s Department
and Name
values:
创建或修改过程[dbo].(GetEmployeesWithDepartment)
@id INT
AS
BEGIN
SET NOCOUNT ON;
SELECT [E].*, [D].[姓名]AS[部门]
FROM [dbo].[Employee] [E]
INNER JOIN [dbo].[部门][D] ON [E].[departmentd] = [D].[Id]
WHERE [E].[Id] >= @id
END
Let’s say we want to determine the department associated with the first employee listed in a 简单测试数据库 (in our example, the first employee listed is John in Engineering). We would like to execute this SP from our C# code, so let’s configure EF Core to support calling GetEmployeesWithDepartment
作为参数化SP.
注意:在继续之前, 构建数据库 using the Scaffold-DbContext
命令,或使用 创建上下文脚手架
command in .NET Core CLI.
首先,我们将创建一个名为 GetEmployeesWithDepartment_Result.cs
然后定义复杂返回类型的结构:
公共类GetEmployeesWithDepartment_Result
{
public int Id { get; set; }
public string Name { get; set; }
public int DepartmentId { get; set; }
public int? ManagerId { get; set; }
public int Salary { get; set; }
public decimal? Bonus { get; set; }
public string Department { get; set; }
}
使用Microsoft SQL Server as the database server, we can explicitly verify the SP result column types by executing the sp_describe_first_result_set
command:
EXEC sp_describe_first_result_set N'[dbo].(GetEmployeesWithDepartment)”
该命令显示 存储过程的列 以及相关的类型列表. With the result type defined, we move on to updating our EF model.
DbContext
FileWe are ready to incorporate the result model into our application’s EF Core DbContext
file. EF provides an elegant approach to extending an application’s data model. Such 支持扩展 使用分部类,特别是使用 OnModelCreatingPartial
method. To keep EF Core’s scaffolding tools from modifying our custom code, we’ll add our result model to EFCoreSPContext.SP.cs
,一个局部c#类:
using EFCoreSP.Data.SPs;
using Microsoft.EntityFrameworkCore;
using System.Collections.Generic;
using System.Linq;
名称空间EFCoreSP.Data
{
公共部分类EFCoreSPContext: DbContext
{
public virtual DbSet
GetEmployeesWithDepartment_Results { get; set; }
//我们将在这里添加后续更改
}
}
Here’s how EFCoreSPContext.SP.cs
looks in our repository. We now need to add code that identifies our model’s primary key, if one is present.
We’ll indicate whether our SP’s result set has a key value by configuring our model in an OnModelCreatingPartial
method in our EFCoreSPContext
definition.
如果结果集有键值,则使用 HasKey
method to explicitly identify the property associated with that key value:
partial void OnModelCreatingPartial(ModelBuilder modelBuilder)
{
modelBuilder.Entity(entity =>
entity.HasKey(e => e.Id));
}
如果实体没有键值,则使用 HasNoKey
method instead:
partial void OnModelCreatingPartial(ModelBuilder modelBuilder)
{
modelBuilder.Entity(entity =>
entity.HasNoKey());
}
我们的模型定义现在已经完成了. We’re ready to call the SP and retrieve our example employee data.
To simplify calling our SP, we’ll add one more public method to the EFCoreSPContext
file. 方法的定义接受 Employee.Id
所提供的价值传递了它 Id
to the SP, and retrieves the generated complex results as a list:
public IEnumerable
SP_GetEmployeesWithDepartment (int id)
{
return this.GetEmployeesWithDepartment_Results
.FromSqlInterpolated($”[dbo].(GetEmployeesWithDepartment) {id}”)
.ToArray();
}
Our DbContext
file is now ready to call a stored procedure and return a complex type result set, and our code is complete. 返回到我们的示例查询, we can use a simple command to return the department and other data associated with the first employee in our database:
var employees = dbContext.SP_GetEmployeesWithDepartment (1);
我们应用了一个简单的, 然而聪明和强大, solution to return a non-database entity from a stored procedure. This approach entails relatively few lines of supporting code and yields a considerable payoff when using EF Core to retrieve complex results.
The editorial team of the Toptal Engineering Blog extends its gratitude to 亚历山大Skogorev for reviewing the technical content and code samples presented in this article.
微软从 .NET Framework to .NET Core. With its lightweight architecture that allows developers to extend the cross-platform framework, EF Core is a popular tool for accessing a data layer from a .. NET语言,通常是c#.
EF是一个对象关系映射器 .NET Framework. 而EF不再积极发展, EF Core is Microsoft’s current object-database mapper for .NET (i.e., .NET Core).
Yes, EF Core supports stored procedures, much like its predecessor, Entity Framework.
You may execute a stored procedure in EF Core by using the DbSet
Yes, a stored procedure can be imported as a function with Entity Framework in an .edmx file.
英国伦敦
2020年7月13日成为会员
Pankaj is a back-end developer and Microsoft Certified Professional with more than 18 years of experience within the Microsoft ecosystem, including C#, VB.NET, SQL Server, and cloud computing with Microsoft Azure. He has worked as a .NET developer at companies including Granicus, Gartner, and Jacobs.
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