MVC应用程序中设置的数据库上下文可以使用多长时间？

Question

I have the following in my MVC Application:

namespace WebUx.Areas.User.Controllers
{
    [Authorize]
    [InitializeSimpleMembership]
    public class AccountController : Controller
    {

Plus:

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public sealed class InitializeSimpleMembershipAttribute : ActionFilterAttribute
{
    private static SimpleMembershipInitializer _initializer;
    private static object _initializerLock = new object();
    private static bool _isInitialized;

    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        // Ensure ASP.NET Simple Membership is initialized only once per app start
        LazyInitializer.EnsureInitialized(ref _initializer, ref _isInitialized, ref _initializerLock);
    }

    private class SimpleMembershipInitializer
    {
        public SimpleMembershipInitializer()
        {
            System.Diagnostics.Debug.Write("Set Initializer\n");
            Database.SetInitializer<UsersContext>(null);


            try
            {
                using (var context = new UsersContext())
                {
                    if (!context.Database.Exists())
                    {
                        // Create the SimpleMembership database without Entity Framework migration schema
                        ((IObjectContextAdapter)context).ObjectContext.CreateDatabase();
                    }
                }

                WebSecurity.InitializeDatabaseConnection("DefaultConnection", "UserProfile", "UserId", "UserName", autoCreateTables: true);

            }

I understand that when there's a call to the account controller then this will set the DB context but once this is set will it stay set for my application. What about later on for other users who connect. Will the DB context always be available?

The reason I am asking this is that I have other information that I want to store in a table and access with Web API. Should I code in something similar for these controllers so that each time I check that there's a DB context available or could I just use this?

Answer 1

The connection is tightly coupled to the DbContext . As a result, the connection will only be open when your class which inherits DbContext , UsersContext in your case, retains its scope.

In your example, UsersContext is scoped to the using block.

using (var context = new UsersContext())
{
 //some actions
}

Therefore, once "some actions" are finished, the connection will close and any attempt to access lazy loading will throw an exception stating the connection is no longer available. Every time you need to access your database, you should start a new connection in my opinion. What you want to make sure is that you only make one actual trip to the database. Make sure that your query is optimized so that you do not make multiple trips to the database instead of just doing it all at once as that will affect your performance.

Edit

As a side note, the using block breaks down into this:

try{
 var context = new UsersContext();
 //some actions
}finally{
 context.Dispose();
}