實體框架代碼在分離對象上的第一次更新

Question

如何通過使用附加特定對象來更新模型及其子代？

我使用存儲庫模式，看起來像這樣的舊實體框架：

public User UpdateUser(User user, IEnumerable<System.Linq.Expressions.Expression<Func<User, object>>> properties) 
    { 
     if (user.UserId == 0) 
     { 
      db.Users.Attach(user); 
     } 
     else 
     { 
      db.Users.Attach(user); 
      ObjectStateEntry entry = db.ObjectStateManager.GetObjectStateEntry(user); 
      foreach (var selector in properties) 
      { 
       string propertyName = PropertyToString(selector.Body); 
       entry.SetModifiedProperty(propertyName); 
      } 
     } 

     context.SaveChanges(); 
     return user; 
    } 

    private static string PropertyToString(Expression selector) 
    { 
     switch (selector.NodeType) 
     { 
      case ExpressionType.MemberAccess: 
       return ((selector as MemberExpression).Member as PropertyInfo).Name; 
       break; 

      case ExpressionType.Convert: 
       //Needed to recognize bool datatype 
       return (((selector as UnaryExpression).Operand as MemberExpression).Member as PropertyInfo).Name; 

       break; 
     } 
     throw new InvalidOperationException(); 
    } 

但現在，代碼優先不支持db.ObjectStateManager。如何在分離對象的特定屬性上運行更新？

Answer 1

你可以嘗試使用：

context.Entry(user).Property(u => u.Body).IsModified = true; 

其中上下文是您DbContext派生類的instace。

Answer 2

嘗試

var adapter = (IObjectContextAdapter)context; 
adapter.ObjectContext.ObjectStateManager ...