ASP.net/Linq的奇怪缓存问题

Question

I'm writing an application involving storing a profile. I'm using Linq to access the database, but having a weird issue when saving a profile. When I save it, it writes to the DB correctly - but when I leave the page and come back, the old values still remain in profile form.

My profile page:

if(!Page.IsPostBack) {
    Profile p = Student.GetProfile(Int32.Parse(Session["userID"].ToString()));
    if (p != null)
    {
          FirstNameTextBox.Text = p.FirstName;
          LastNameTextBox.Text = p.LastName;
          Address1TextBox.Text = p.Address1;
          .....
    }

And my Student class:

    public static Profile GetProfile(int uID)
    {
        var profile = (from p in db.Profiles
                       where p.uID == uID
                       select p).FirstOrDefault();
        return profile;
    }

I'm not doing any fancy caching anywhere, so not sure where the old values are stored...

** EDIT **

So, it seems that it's down to a global LinqDataContext. In my Student class, I had:

public class Student
{
    private static LinqClassesDataContext db = new LinqClassesDataContext() { CommandTimeout = 36000 };

    public static Profile GetProfile(int uID)
    {
            var profile = (from p in db.Profiles
                           where p.uID == uID
                           select p).FirstOrDefault();
            return profile;   
    }

If I give the GetProfile method it's own DataContext, problem solved.

Still being very new to Linq, what's the best way to have a class with numerous methods that use the same access to a database? Having a global context like this? Or each method using it's own data context?

Answer 1

Assuming you're storing the userID in Session["userID"] somewhere and not clearing it out when you save, this could be where the "caching" occurs. Session objects will live (roughly) for the life of the browser session (or the life of the server process if in-memory session is enabled).

Answer 2

我想即使linq将查询发送到数据库，它也会使用存储在cache中的旧值。因此，如果要使用新值，则必须清除缓存。

Answer 3

Going on your added comments my guess is that the page you are getting is cached by the browser / http server. If the url is the same as a previously requested page some default setting will tell the browser / server to use the cache html. To avoid this and get new html for each request you could try adding a meta tag within the head tags of your html.

<meta http-equiv="Pragma" CONTENT="no-cache">

Answer 4

It ended up being the DataContext I was using. I'm not exactly sure why this fixed the issue, but I changed my class from:

public class Student
{
   private static LinqClassesDataContext db = new LinqClassesDataContext() { CommandTimeout = 36000 };

   public static Profile GetProfile(int uID)
   {
        var profile = (from p in db.Profiles
                       where p.uID == uID
                       select p).FirstOrDefault();
        return profile;   
   }
}

to:

public class Student
{
   public static Profile GetProfile(int uID)
   {     
        LinqClassesDataContext db = new LinqClassesDataContext();
        var profile = (from p in db.Profiles
                       where p.uID == uID
                       select p).FirstOrDefault();
        return profile;   
   }
}