c# – 在实体类中访问LINQ-2-SQL DataContext

首先,为所有实体创建一个接口,以实现从INotifyPropertyChanging继承的接口.这是用来连接一些扩展方法,并保持我们的实现很好分离.在我的情况下,该接口称为ISandboxObject：

public interface ISandboxObject : INotifyPropertyChanging
{
    // This is just a marker interface for Extension Methods
}

然后创建一个新的静态类以包含一个扩展方法来获取DataContext.这通过在INotifyPropertyChanging.PropertyChanging事件附加的LINQ Change Tracker上查找事件处理程序来实现.一旦找到了更改跟踪器,我们就可以从中获取DataContext：

/// <summary>
    /// Obtain the DataContext providing this entity
    /// </summary>
    /// <param name="obj"></param>
    /// <returns></returns>
    public static DataContext GetContext(this ISandboxObject obj)
    {
        FieldInfo fEvent = obj.GetType().GetField("PropertyChanging",BindingFlags.NonPublic | BindingFlags.Instance);
        MulticastDelegate dEvent = (MulticastDelegate)fEvent.GetValue(obj);
        Delegate[] onChangingHandlers = dEvent.GetInvocationList();

        // Obtain the ChangeTracker
        foreach (Delegate handler in onChangingHandlers)
        {
            if (handler.Target.GetType().Name == "StandardChangeTracker")
            {
                // Obtain the 'services' private field of the 'tracker'
                object tracker = handler.Target;
                object services = tracker.GetType().GetField("services",BindingFlags.NonPublic | BindingFlags.Instance).GetValue(tracker);

                // Get the Context
                DataContext context = services.GetType().GetProperty("Context").GetValue(services,null) as DataContext;
                return context;
            }
        }

        // Not found
        throw new Exception("Error reflecting object");
    }

现在你有一个很好的扩展方法,它可以为来自任何实现ISandboxObject的对象提供一个DataContext.在使用它之前,请先做一些更多的错误检查！