mysql - Visual Studio 2010 + MySQL + Entity Framework

Question

我正在尝试使用 Entity Framework 连接 MySQL 数据库。我的 VB.net 代码如下:

    Dim context As sql688249Entities = New sql688249Entities()
    Dim nsv As sinhvien = New sinhvien()
    nsv.MSSV = Int(234)
    nsv.Hoten = "Thanh"
    nsv.Diachi = "Phu Yen"
    context.sinhviens.AddObject(nsv)
    context.SaveChanges()
    DataGridView1.DataSource = context.sinhviens

但它不起作用。如果我删除 context.Savechanges() 它没有问题。我不明白为什么我不能将记录插入数据库。

Answer 1

您尝试添加的类具有用于构建记录的Create... 方法。确保您也增加了表的主键字段。

Using context As sql688249Entities = New sql688249Entities()
  Dim id As Integer = 1 ' get the last id or use this default
  Dim lastOne = context.sinhviens.OrderByDescending(Function(s) s s.MSSV).FirstOrDefault
  If lastOne IsNot Nothing Then
    id = lastOne.MSSV + 1 ' add one to have a valid next id
  End If
  Dim nsv As sinhvien = sinhvien.Createsinhvien(id, "Thanh", "Phu Yen")
  context.sinhviens.AddObject(nsv)
  DataGridView1.DataSource = context.sinhviens
  context.SaveChanges()
End Using