在VB.NET中找不到AddOrUpdate()方法

我正在尝试将 c#代码转换为VB代码:

在c#代码中，它可以调用AddOrUpdate方法，但当我在VB中编写它时，它在智能感知中找不到。

c#代码:

  protected override void Seed(eManager.Web.Infrastructure.DepartmentDB context){
         context.Departments.AddOrUpdate( d => d.Name,
                  new Department() { Name = "Engineering"},
                  new Department() { Name = "Sales"}
         );
     }

VB代码:

但是当我在VB中编写方法AddOrUpdate()时，我找不到它。DepartmentDB类的声明如下:

 Imports System
    Imports System.Collections
    Imports System.Collections.Generic
    Imports System.Linq
    Imports System.Text
    Imports System.Threading.Tasks
    Imports System.Data.Entity
    Imports eManager.Domain
    Public Class DepartmentDB
       Inherits DbContext
       Implements IDepartmentDataSource
    Private _DBEmployees As DbSet(Of Employee)
    Private _DBDepartments As DbSet(Of Department)
    Public ReadOnly Property Departments As IQueryable(Of Department) Implements IDepartmentDataSource.Departments
        Get
            Return _DBDepartments
        End Get
    End Property

    Public ReadOnly Property Employees As IQueryable(Of Employee) Implements IDepartmentDataSource.Employees
        Get
            Return _DBEmployees
        End Get
    End Property
End Class

Imports System.Data.Entity.Migrations