c# - DBContext 自定义验证

Question

对 DBContext 比较陌生，尝试在 DBContext 中编写自定义验证而不实现IValidatableObject 接口(interface)或ValidateEntity 覆盖。

例如对于具有以下内容的部门实体:姓名过境#盲点

这是保存逻辑的片段:

public static Boolean saveDepartmentDetails(Department dept, out string errorMessage)
{
Boolean isSuccessful = false;
Int32 iRetVal = 0;
errorMessage = string.Empty;

using (OnlineFormsEntities context = new OnlineFormsEntities())
{
    if (dept != null)
    {
        if (dept.DepartmentID > 0)
        {
            //Todo: I know this is wrong.
            if (context.Departments.Where(d => d.DepartmentName.ToLower() == dept.DepartmentName.ToLower() && d.DepartmentID != dept.DepartmentID).Count() > 0)
            {
                errorMessage = "A Department with the given name already exists.";
                return false;
            }
            if (context.Departments.Where(d => d.Transit.ToLower() == dept.Transit.ToLower() && d.DepartmentID != dept.DepartmentID).Count() > 0)
            {
                errorMessage = "A Department with the given Transit # already exists.";
                return false;
            }

            context.Departments.Attach(dept);
            context.Entry(dept).State = EntityState.Modified;
        }
        else
        {
            if (context.Departments.Where(d => d.DepartmentName.ToLower() == dept.DepartmentName.ToLower()).Count() > 0)
            {
                errorMessage = "A Department with the given name already exists.";
                return false;
            }
            if (context.Departments.Where(d => d.Transit.ToLower() == dept.Transit.ToLower()).Count() > 0)
            {
                errorMessage = "A Department with the given Transit # already exists.";
                return false;
            }

            context.Departments.Add(dept);
        }

        try
        {
            iRetVal = context.SaveChanges();
        }
        catch (System.Data.OptimisticConcurrencyException opEx)
        {
            errorMessage = opEx.Message;
            ((IObjectContextAdapter)context).ObjectContext.Refresh(RefreshMode.ClientWins, dept);
            iRetVal = context.SaveChanges();
        }
        isSuccessful = (iRetVal > 0) ? true : false;
    }
}
return isSuccessful;
}

我需要有关更新逻辑的帮助。或者更好的方法来编写此 SaveDepartmentDetails。

Answer 1

我建议将所有通用逻辑提取到您正在保存的同一类中的验证方法中(即返回 bool 值的方法:如果通过则为 True，如果通过则为 False如果没有。您也可以将错误消息用作 out 参数):

private bool ValidateDept(OnlineFormsEntities context, Department dept, out string errorMessage)
{
  errorMessage = string.empty;

  if (context.Departments.Any(d => d.DepartmentName.ToLower() == dept.DepartmentName.ToLower() && d.ID != dept.ID))
   {
     errorMessage = "A Department with the given name already exists.";
     return false;
   }
 if (context.Departments.Any(d => d.Transit.ToLower() == dept.Transit.ToLower() && d.ID != dept.ID))
   {
     errorMessage = "A Department with the given Transit # already exists.";
     return false;
  }
 return true;
}

然后，这样做将允许您在保存方法的开头调用此验证方法，然后仅在它通过后才执行添加/附加。