Question

I’m trying to find a way to have the DataContext available from within Entities.

I want to do something like this:

partial public class MyEntity

    public DataContext as MyDataContext

    private sub OnLoaded()
        Me.DataContext = <the context that retrieved this instance>
    end sub

end class

First, can something like this be done?
Second, assuming that I’m not going to use this entity with any other DataContext, is there any dangers or gotchas in doing such a thing?

This is the way I do it currently:

partial public class MyDataContext

    public function GetMyEntity(byval id as integer) as MyEntity
        dim o = MyEntities.SingleOrDefault(function(e) e.id = id)
        if o isnot nothing then o.DataContext = Me
        return o
    end function

end class

Answer 1

You could use a singleton pattern on the DataContext, but you will need some kind of lifetime management on it, as it is not good to keep it around to long. (request ends dispose it maybe)

Example in C#, but I hope you can understand it.

public class MyDataContext
{       
    public static MyDataContext Current 
    {
        get
        {
            MyDataContext context = (MyDataContext)HttpContext.Current.Items["Context"];
            if(context == null)
            {
                context = new MyDataContext();
                HttpContext.Current.Items["Context"] = context;
            }
            return context;
        }
    }
}

public class MyEntity
{
    public MyDataContext DataContext
    {
        get{ return MyDataContext.Current;}
    }
}

In Global.asax you can hook up the event Application_EndRequest and call MyDataContext.Current.Dispose(); to dispose of the context manually instead of waiting for the GC to do it.