这是一个简单的CRUD应用程序，我正在使用它来学习它是如何工作的。我以前使用过实体框架，但对它的工作原理知之甚少。这个应用程序有一个数据库，有一个表，Employee，有6个常见类型的列。我下载了System.Text.Json之前编写的同一应用程序的工作副本，因此数据库连接正常工作。
GetEmployee.razor中的调用是：
@code {
private Employee[] empList;
protected override async Task OnInitializedAsync()
{
try
{
empList = await Http.GetFromJsonAsync<Employee[]>("/api/Employee/Index");
}
catch (Exception ex)
{
string foo = ex.ToString();
}
}
}
namespace Clean.Server.Api
{
public partial class ManagementContext : DbContext
{
public ManagementContext()
{
}
public ManagementContext(DbContextOptions<ManagementContext> options)
: base(options)
{
}
public virtual DbSet<Employee> Employee { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
if (!optionsBuilder.IsConfigured)
{
#warning To protect potentially sensitive information in your connection string, you should move it out of source code. See http://go.microsoft.com/fwlink/?LinkId=723263 for guidance on storing connection strings.
optionsBuilder.UseSqlServer("Server=MtLyell\SQLEXPRESS;Database=Management;Integrated Security=True;");
}
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Employee>(entity =>
{
entity.Property(e => e.Designation)
.HasMaxLength(100)
.IsUnicode(false);
entity.Property(e => e.Email)
.HasMaxLength(20)
.IsUnicode(false);
entity.Property(e => e.Location)
.IsRequired()
.HasMaxLength(50)
.IsUnicode(false);
entity.Property(e => e.Name)
.IsRequired()
.HasMaxLength(100)
.IsUnicode(false);
});
OnModelCreatingPartial(modelBuilder);
}
partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
}
}
amespace Clean.Server.Api
{
public partial class Employee
{
public long EmployeeId { get; set; }
public string Name { get; set; }
public string Designation { get; set; }
public string Email { get; set; }
public string Location { get; set; }
public long PhoneNumber { get; set; }
}
}
namespace Clean.Server.Api
{
public interface IEmployeAccessLayer
{
IEnumerable<Employee> GetAllEmployees();
void AddEmployee(Employee employee);
void UpdateEmployee(Employee employee);
Employee GetEmployeeData(long id);
void DeleteEmployee(long id);
}
public class EmployeAccessLayer : IEmployeAccessLayer
{
private ManagementContext _context;
public EmployeAccessLayer(ManagementContext context)
{
_context = context;
}
//To Get all employees details
public IEnumerable<Employee> GetAllEmployees()
{
try
{
return _context.Employee.ToList();
}
catch(Exception ex)
{
throw;
}
}
//To Add new employee record
public void AddEmployee(Employee employee)
{
try
{
_context.Employee.Add(employee);
_context.SaveChanges();
}
catch
{
throw;
}
}
//To Update the records of a particluar employee
public void UpdateEmployee(Employee employee)
{
try
{
_context.Entry(employee).State = EntityState.Modified;
_context.SaveChanges();
}
catch
{
throw;
}
}
//Get the details of a particular employee
public Employee GetEmployeeData(long id)
{
try
{
Employee employee = _context.Employee.Find(id);
return employee;
}
catch
{
throw;
}
}
//To Delete the record of a particular employee
public void DeleteEmployee(long id)
{
try
{
Employee emp = _context.Employee.Find(id);
_context.Employee.Remove(emp);
_context.SaveChanges();
}
catch
{
throw;
}
}
}
}
namespace Clean.Server.Controllers
{
public class EmployeeController : ControllerBase
{
IEmployeAccessLayer _employee;
public EmployeeController(IEmployeAccessLayer employee)
{
_employee = employee;
}
[HttpGet]
[Route("api/Employee/Index")]
public IEnumerable<Employee> Index()
{
return _employee.GetAllEmployees();
}
[HttpPost]
[Route("api/Employee/Create")]
public void Create([FromBody] Employee employee)
{
if (ModelState.IsValid)
this._employee.AddEmployee(employee);
}
[HttpGet]
[Route("api/Employee/Details/{id}")]
public Employee Details(int id)
{
return _employee.GetEmployeeData(id);
}
[HttpPut]
[Route("api/Employee/Edit")]
public void Edit([FromBody]Employee employee)
{
if (ModelState.IsValid)
this._employee.UpdateEmployee(employee);
}
[HttpDelete]
[Route("api/Employee/Delete/{id}")]
public void Delete(int id)
{
_employee.DeleteEmployee(id);
}
}
}
更完整的错误消息是：
不支持提供的 ContentType;支持的类型是"application/json"和结构化语法后缀"application/+json">
要将实体对象转换为 Json，我尝试将JsonSerializer.Serialize()应用于EmployeeAccessLayer.cs中的GetAllEmployees方法。结果是：
无法将类型字符串隐式转换为 System.Collections.Generic.IEnumerable
我最终可能会想出如何做到这一点。
return JsonSerializer.Serialize(_context.Employee.ToList());
序列化是否EmployeeAccessLayer.cs进行此转换的正确想法和位置？
如果是这样，如何将其转换为正确的类型？
或者 EF 中是否有适合我的设置？
在 Startup 中.cs我需要注册 ManagementContext 和 IemployeAccessLayer，我做到了：
public static string Connection { get; set; }
Connection = Configuration.GetConnectionString("EmployeeDatabase");
services.AddDbContext<ManagementContext>(options => options.UseSqlServer(Connection));
services.AddScoped<IEmployeAccessLayer, EmployeAccessLayer>();
在管理上下文中.cs我更改了 OnConfiguring：
optionsBuilder.UseSqlServer(Clean.Server.Startup.Connection);
在razor 文件中似乎有效的 json 命令(最小测试(是： GetFromJsonAsync， PutAsJsonAsync， 删除异步， PostAsJson异步