C#：如何使用 Entity Framework Core 将记录检索到存储过程中？

Question

我已经使用 Angular 创建了一个新的 ASP.NET Core 2.1 Web 应用程序

Visual Studio 创建一个使用 Entity Framework Core 和 ASP.NET Core MVC 的项目。

我有这个问题：我必须从存储过程中读取记录：

CREATE PROCEDURE GetEmployees
    (@PageIndex INT,
     @PageSize INT)
AS
BEGIN
    SELECT * 
    FROM employee 
    ORDER BY id 
        OFFSET @PageSize * (@PageIndex - 1) ROWS 
        FETCH NEXT @PageSize ROWS ONLY;

    SELECT COUNT(*) AS totalCount 
    FROM employee;
END

我找到了a question that almost solves my question，但不幸的是还是有一些东西不起作用。

这是我的代码：

namespace Angular.Controllers
{
    //[Produces("application/json")]
    [Route("api/Employees")]
    public class EmployeesController : Controller
    {
        private readonly ApplicationDbContext _context;

        public EmployeesController(ApplicationDbContext context)
        {
            _context = context;
        }

        // GET: api/Employees/pageIndex/1/pageSize/1
        [HttpGet("pageIndex/{pageIndex}/pageSize/{pageSize}")]
        public Task<IActionResult> GetEmployeeP([FromRoute] int pageIndex, int pageSize)
        {
            SqlParameter pageIndexParam = new SqlParameter("@PageIndex", SqlDbType.Int);
            pageIndexParam.Value = pageIndex;

            SqlParameter pageSizeParam = new SqlParameter("@pageSize", SqlDbType.Int);
            pageSizeParam.Value = pageSize;

            // SqlParameter pageIndexParam = new SqlParameter("@PageIndex", pageIndex);
            // SqlParameter pageSizeParam = new SqlParameter("@pageSize", pageSize);

            var cmd = _context.Database.GetDbConnection().CreateCommand();
            cmd.CommandText = "GetEmployees"; // The name of the stored procedure
            cmd.CommandType = System.Data.CommandType.StoredProcedure;

            // the 2 parameters to be passed to the procedure
            var param = cmd.CreateParameter();
            param.ParameterName = "@PageIndex";
            param.Value = pageIndexParam;
            cmd.Parameters.Add(param);

            var param2 = cmd.CreateParameter();
            param2.ParameterName = "@pageSize";
            param2.Value = pageSizeParam;
            cmd.Parameters.Add(param2);

            try
            {
                // connection.Open();
                // _context.Database.GetDbConnection().Open(); // it crashes after this line
                _context.Database.OpenConnection(); // it crashes after this line
                var dr = cmd.ExecuteReader(); // ArgumentException: No mapping exists from object type System.Data.SqlClient.SqlParameter to a known managed provider native type.
                List<Employee> listEmp = new List<Employee>();

                while (dr.Read())
                {
                    // Is there a faster way to read the whole record?
                    // Or should I write a line for each field?
                    Employee emp = new Employee();
                    emp.ID = System.Int32.Parse(dr["id"].ToString());
                    emp.Fname = dr["FName"].ToString();
                    emp.email = dr["email"].ToString();
                    emp.Lname = dr["LName"].ToString();
                    listEmp.Add(emp);

                    dr.NextResult();
                }

                return Ok(listEmp);
            }
            catch (Exception ex)
            {
                // how can I return an error in json format?
                throw;
            }
        }
    }
}

问题出在脚本ExecuteReader所在的那一行：

ArgumentException：不存在从对象类型 System.Data.SqlClient.SqlParameter 到已知托管提供程序本机类型的映射。

我使用 Microsoft SQL Server 在 Startup.cs 文件中，我是这样配置连接的：

services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer("Server=localhost\\SQLEXPRESS;Database=master;Trusted_Connection=True;"));

你能帮帮我吗？

也许我设法正确传递了参数（请参阅我的解决方案，在答案中）但我无法提取记录

Answer 1

我在当前项目中使用 Entity Framework Core，并使用以下方法通过存储过程获取数据。

首先在存储过程中创建一个具有相同数量和名称的属性的模型。

假设您仅通过存储过程选择 EmployeeName ,EmployeeId。

型号。

 public class EmployeeModel
  {
    public string EmployeeName { get; set; }
    public int EmployeeId{ get; set; }
  }

转到您的 Db 上下文文件并注册您的自定义模型。

 public partial class ApplicationDbContext: DbContext
 {
 public virtual DbSet<EmployeeModel> EmployeeModel{ get; set; }
 protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<EmployeeModel>(entity =>
        { 
        });
        }
    }

你的控制器

 [HttpGet("pageIndex/{pageIndex}/pageSize/{pageSize}")]
    public Task<IActionResult> GetEmployeeP([FromRoute] int pageIndex, int pageSize)
    {
    List<EmployeeModel> employeeList = new List<EmployeeModel>();
    employeeList = _context.EmployeeModel.FromSql("GetEmployees 
    @PageIndex,@PageSize", 
    new SqlParameter("@PageIndex", pageIndex),
    new SqlParameter("@PageSize", pageSize)).ToList();
    return Ok(employeeList);
    }

Answer 2

部分解谜：

    // GET: api/Employees/pageIndex/1/pageSize/1
    [HttpGet("pageIndex/{pageIndex}/pageSize/{pageSize}")]
    public async Task<IActionResult> GetEmployeeP([FromRoute] int pageIndex, int pageSize)
    {
        _context.Database.OpenConnection();

        var cmd = _context.Database.GetDbConnection().CreateCommand();
        cmd.CommandType = System.Data.CommandType.StoredProcedure;
        /*
         * it's the same, it also works with these lines
                    SqlParameter pageIndexParam = new SqlParameter("PageIndex", pageIndex);
                    SqlParameter pageSizeParam = new SqlParameter("PageSize", pageSize);
                    cmd.Parameters.Add(pageIndexParam);
                    cmd.Parameters.Add(pageSizeParam);
        */

        cmd.CommandText = "GetEmployees"; // The name of the stored procedure

        // the 2 parameters to be passed to the procedure
        var param = cmd.CreateParameter();
        param.ParameterName = "@PageIndex";
        param.Value = pageIndex;
        cmd.Parameters.Add(param);

        var param2 = cmd.CreateParameter();
        param2.ParameterName = "@PageSize";
        param2.Value = pageSize;
        cmd.Parameters.Add(param2);




        try
        {
            System.Data.Common.DbDataReader dr = cmd.ExecuteReader();
            List<Employee> listEmp = new List<Employee>();

            while (dr.Read())
            {
                // Is there a faster way to read the whole record?
                // Or should I write a line for each field?
                Employee emp = new Employee();
                //emp.ID = System.Int32.Parse(dr["id"].ToString());
                emp.ID = 1; //  it crashes after this line
                emp.Fname = dr["FName"].ToString(); // System.IndexOutOfRangeException: FName

                /*
                 * it doesn't see the columns :-(
                                    emp.email = dr["email"].ToString();
                                    emp.Lname = dr["LName"].ToString();
                */
                listEmp.Add(emp);
                dr.NextResult();
            }
            return Ok(listEmp);
        }
        catch (Exception ex)
        {
            // how can I return an error in json format?
            throw;
        }



    }

现在它稍后崩溃 当它试图读取记录时

emp.Fname = dr["FName"].ToString();

System.IndexOutOfRangeException: FName

它没有看到列 :-(

Answer 3

根据@bricelam 回答here 的内容，你可以试试这个吗？

     public Task<IActionResult> GetEmployeeP([FromRoute] int pageIndex, int pageSize)
    {
        var cmd = _context.Database.GetDbConnection().CreateCommand();
        cmd.CommandText = "GetEmployees";
        cmd.CommandType = System.Data.CommandType.StoredProcedure;

        cmd.Parameters.AddWithValue("@PageIndex", pageIndex);
        cmd.Parameters.AddWithValue("@PageSize", pageSize);

        try
        {
          //...
        }
   }

如果发生任何事情，请告诉我。