Question

我有以下情况：

public void UpdateEmployee(int empId, int deptId, int level)
{
  Employee emp = GetEmployee(empId);
  emp.DeptId = deptId;
  emp.Level = level;

  using (var mye = new MyEntity())
  {
    //this is having no effect?
    wc.SaveChanges()
  }
}

我不确定如何将Employee对象更新保存回数据库。员工确实存在于数据库中。使用区块应该包含哪些内容？

Answer 1

在修改，修改，然后保存更改之前附加它。

public void UpdateEmployee(int empId, int deptId, int level)
{
  Employee emp = GetEmployee(empId);

  using (var dbContext = new MyDbContext())
  {
   dbContext.Employees.Attach(emp);
   emp.DeptId = deptId;
   emp.Level = level;
   //this is having no effect?
   dbContext.SaveChanges()
  }
}

您也可以附加它，然后将状态设置为Modified：

public void UpdateEmployee(int empId, int deptId, int level)
{
  Employee emp = GetEmployee(empId);
  emp.DeptId = deptId;
  emp.Level = level;    

  using (var dbContext = new MyDbContext())
  {
   dbContext.Employees.Attach(emp);
   dbContext.Entry(emp).State = EntityState.Modified;
   dbContext.SaveChanges()
  }
}

如果您只想在更新中发送这些字段而不是所有列：

public void UpdateEmployee(int empId, int deptId, int level)
{
  Employee emp = GetEmployee(empId);
  emp.DeptId = deptId;
  emp.Level = level;    

  using (var dbContext = new MyDbContext())
  {
   dbContext.Employees.Attach(emp);
   dbContext.Entry(emp).Property(p => p.DeptId).IsModified = true;
   dbContext.Entry(emp).Property(p => p.Level).IsModified = true;
   dbContext.SaveChanges()
  }
}

Answer 2

您需要在ObjectContext上调用SaveChanges

如何使用EntityFramework将对象更新保存到数据库？

2 个答案: