ASP.Net WebAPI URL不返回任何数据

Question

我正在使用Northwind数据库，试图了解Asp.Net的WebAPI。

我的模型/控制器/全局文件如下所示。

当我导航到localhost：xxxx / api / employees / 5时，它正确地转到了正确的控制器：

' GET /api/employees/5
Public Function GetValue(ByVal ID As Integer) As Employee
    Dim emp As Employee = db.Employees.Find(ID)
    Return emp
End Function

...但是emp返回Null / Nothing。

Northwind数据库肯定有数据：

有人能看到我出错的地方吗？

谢谢，Mark

---

型号/ Employee.vb：

Imports System.Data.Entity

  Namespace MvcApplication21
  Public Class Employee
    Public Property EmployeeID() As Integer
    Public Property FirstName() As String
    Public Property LastName() As String
  End Class

  Public Class EmployeeDBContext
    Inherits DbContext
    Public Property Employees() As DbSet(Of Employee)
  End Class
End Namespace

控制器/ EmployeesController.vb

Imports System.Web.Http
Imports MvcApplication21
Imports MvcApplication21.MvcApplication21

Public Class EmployeesController
Inherits ApiController

Private db As New EmployeeDBContext

' GET /api/employees
Public Function GetValues() As IEnumerable(Of String)
    Return New String() {"value1", "value2"}
End Function

' GET /api/employees/5
Public Function GetValue(ByVal EmployeeID As Integer) As Employee
    Dim employee As Employee = db.Employees.Find(EmployeeID)
    Return employee
End Function

的Web.config：

<configuration>
  <connectionStrings>
    <add name="DefaultConnection" connectionString="Data Source=.\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True" providerName="System.Data.SqlClient" />
  </connectionStrings>

Global.asax.vb

Imports System.Web.Http
Imports System.Web.Optimization

Public Class WebApiApplication
 Inherits System.Web.HttpApplication

 Shared Sub RegisterGlobalFilters(ByVal filters As GlobalFilterCollection)
    filters.Add(New HandleErrorAttribute())
 End Sub

 Shared Sub RegisterRoutes(ByVal routes As RouteCollection)
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}")

    routes.MapHttpRoute( _
        name:="DefaultApi", _
        routeTemplate:="api/{controller}/{id}", _
        defaults:=New With {.id = RouteParameter.Optional} _
    )

    routes.MapRoute( _
        name:="Default", _
        url:="{controller}/{action}/{id}", _
        defaults:=New With {.controller = "Home", .action = "Index", .id = UrlParameter.Optional} _
    )
 End Sub

Answer 1

路由参数与功能参数之间存在冲突

你问题的第一部分

Public Function GetValue（ByVal ID As Integer）As Employee

在控制器中

Public Function GetValue（ByVal EmployeeID As Integer）As Employee

• 一个人将ID作为参数，另一个人将EmployeeID作为参数

您在路由中使用ID

routes.MapHttpRoute( _         
   name:="DefaultApi", _         
   routeTemplate:="api/{controller}/{id}", _         
   defaults:=New With {.id = RouteParameter.Optional} _     
)