Develop Reference

How to pass the current Session object to a method in a C# class [duplicate]

We can access session data in controllers and views like this:
Session["SessionKey1"]
How do you access Session values from a class other than a controller or view?

I'd use dependency injection and pass the instance of the HttpContext (or just the session) to the class that needs access to the Session. The other alternative is to reference HttpContext.Current, but that will make it harder to test since it's a static object.
public ActionResult MyAction()
{
var foo = new Foo( this.HttpContext );
...
}
public class Foo
{
private HttpContextBase Context { get; set; }
public Foo( HttpContextBase context )
{
this.Context = context;
}
public void Bar()
{
var value = this.Context.Session["barKey"];
...
}
}

You just need to call it through the HttpContext like so:
HttpContext.Current.Session["MyValue"] = "Something";

Here is my version of a solution for this problem. Notice that I also use a dependency injection as well, the only major difference is that the "session" object is accessed through a Singleton
private iSession _Session;
private iSession InternalSession
{
get
{
if (_Session == null)
{
_Session = new SessionDecorator(this.Session);
}
return _Session;
}
}
Here is the SessionDecorator class, which uses a Decorator pattern to wrap the session around an interface :
public class SessionDecorator : iSession
{
private HttpSessionStateBase _Session;
private const string SESSIONKEY1= "SESSIONKEY1";
private const string SESSIONKEY2= "SESSIONKEY2";
public SessionDecorator(HttpSessionStateBase session)
{
_Session = session;
}
int iSession.AValue
{
get
{
return _Session[SESSIONKEY1] == null ? 1 : Convert.ToInt32(_Session[SESSIONKEY1]);
}
set
{
_Session[SESSIONKEY1] = value;
}
}
int iSession.AnotherValue
{
get
{
return _Session[SESSIONKEY2] == null ? 0 : Convert.ToInt32(_Session[SESSIONKEY2]);
}
set
{
_Session[SESSIONKEY2] = value;
}
}
}`
Hope this helps :)

Haven't done it myself, but this sample from Chad Meyer's blog might help (from this post: http://www.chadmyers.com/Blog/archive/2007/11/30/asp.net-webforms-and-mvc-in-the-same-project.aspx)
[ControllerAction]
public void Edit(int id)
{
IHttpSessionState session = HttpContext.Session;
if (session["LoggedIn"] == null || ((bool)session["LoggedIn"] != true))
RenderView("NotLoggedIn");
Product p = SomeFancyDataAccess.GetProductByID(id);
RenderView("Edit", p);
}

I would also wrap all session variables into a single class file. That way you can use intelliSense to select them. This cuts down on the number of paces in code where you need to specify the "strings" for the session.

Changing database at runtime with MVC WebApi 2

I want to change the connection to a database at runtime in a REST Api. I want to put a variable of the request and let the Api decide which connectionstring to use.
For example:
I put the variable "dbid" with the value "develop" in the request header and send it to the Api.
The Api sees the header and gets the correct connectionstring from the web.config.
I have three layers (data, business, api). The data contains EntityFramework to get and set data. Like this:
public class WebsiteContext : IocDbContext, IWebsites
{
public DbSet<Website> Websites { get; set; }
public IEnumerable<Website> GetAll()
{
return Websites.ToList();
}
}
(IoCDbContext.cs)
public class IocDbContext : DbContext, IDbContext
{
public IocDbContext() : base("develop")
{
}
public void ChangeDatabase(string connectionString)
{
Database.Connection.ConnectionString= connectionString;
}
}
In the business I have a class to retrieve data from the datalayer and do some logical stuff (not needed here, but still good for the story).
public class Websites : IWebsites
{
private readonly Data.Interfaces.IWebsites _websiteContext;
#region Constructor
public Websites(Data.Interfaces.IWebsites websiteContext)
{
_websiteContext = websiteContext;
}
#endregion
#region IWebsites implementation
public IEnumerable<Website> GetWebsites()
{
List<Data.Objects.Website> websiteDtos = _websiteContext.GetAll().ToList();
return websiteDtos.Select(web => web.ToModel()).ToList();
}
#endregion
}
public static class WebsiteMapper
{
public static Website ToModel(this Data.Objects.Website value)
{
if (value == null)
return null;
return new Website
{
Id = value.Id,
Name = value.Name
};
}
}
And, last but not least, the controller:
public class WebsiteController : ApiController
{
private readonly IWebsites _websites;
public WebsiteController(IWebsites websites)
{
_websites = websites;
}
public IEnumerable<Website> GetAll()
{
return _websites.GetWebsites().ToList();
}
}
My Unity configuration:
public static void RegisterComponents()
{
var container = new UnityContainer();
container.RegisterType<Business.Interfaces.IWebsites, Websites>();
container.RegisterType<IDbContext, IocDbContext>();
container.RegisterType<IWebsites, WebsiteContext>();
// e.g. container.RegisterType<ITestService, TestService>();
GlobalConfiguration.Configuration.DependencyResolver = new Unity.WebApi.UnityDependencyResolver(container);
DependencyResolver.SetResolver(new UnityDependencyResolver(container));
}
So as you can see the connection string with the name "develop" is used by default. This will return a website with the name "website". Now I would change the header variable "dbid" to "live". The api should see this and should get the connectionstring that corresponds with the name "live". This last part is something I am trying, but nothing works.
This I tried:
Adding session to webapi. This means I break the stateless idea of REST api: not done
Statics cannot work either, because everyone could get the same connectionstring, but its user specific
Google, but most of the examples don't work for me
Searching StackOverflow... See previous point.
This is driving me crazy! There should be a way to change the connectionstring given by a value in a request header, right?

I have the same scenario in a multi-tenant application I created where I use a different connection string for each tenant.
It doesn't matter the implementation you choose, but you have to determine how you are going to differentiate each request per connection string. In my application, I created a custom route value, and used it in the url to differentiate each request. The important thing is to create whatever this mechanism is, and it needs to be the 1st thing you register in your DI framework, on a per request basis.
For example (using Ninject):
private static void RegisterServicdes(IKernel kernel)
{
kernel.Bind<ISiteContext>().To<SiteContext>().InRequestScope();
kernel.Bind<IDbContextFactory>().To<DbContextFactory>().InRequestScope();
// register other services...
}
Rather than your implementation of your DbContext, I would change to be this, then always create your DbContext instance via a DbContextFactory.
public class IocDbContext : DbContext, IDbContext
{
public IocDbContext(string connectionStringType) : base(connectionStringType) { }
}
Then you need to create a DbContextFactory that you use when you create your DbContext, and take the above class as a dependency. Or you can take the dependency into your services, and pass it into the DbContextFactory instead.
public interface IDbContextFactory
{
TestModel CreateContext();
}
public class DbContextFactory : IDbContextFactory
{
private string _siteType;
public DbContextFactory(ISiteContext siteContext)
{
_siteType = siteContext.Tenant;
}
public TestModel CreateContext()
{
return new TestModel(FormatConnectionStringBySiteType(_siteType));
}
// or you can use this if you pass the IMultiTenantHelper dependency into your service
public static TestModel CreateContext(string siteName)
{
return new TestModel(FormatConnectionStringBySiteType(siteName));
}
private static string FormatConnectionStringBySiteType(string siteType)
{
// format from web.config
string newConnectionString = #"data source={0};initial catalog={1};integrated security=True;MultipleActiveResultSets=True;App=EntityFramework";
if (siteType.Equals("a"))
{
return String.Format(newConnectionString, #"(LocalDb)\MSSQLLocalDB", "DbOne");
}
else
{
return String.Format(newConnectionString, #"(LocalDb)\MSSQLLocalDB", "DbTwo");
}
}
}
Then you can use it like so when accessing your DbContext:
public class DbAccess
{
private IDbContextFactory _dbContextFactory;
public DbAccess(IDbContextFactory dbContextFactory)
{
_dbContextFactory = dbContextFactory;
}
public void DoWork()
{
using (IocDbContext db = _dbContextFactory.CreateContext())
{
// use EF here...
}
}
}
ISiteContext interface implementation (for using route).
public interface ISiteContext
{
string Tenant { get; }
}
public class SiteContext : ISiteContext
{
private const string _routeId = "tenantId";
private string _tenant;
public string Tenant { get { return _tenant; } }
public SiteContext()
{
_tenant = GetTenantViaRoute();
}
private string GetTenantViaRoute()
{
var routedata = HttpContext.Current.Request.RequestContext.RouteData;
// Default Routing
if (routedata.Values[_routeId] != null)
{
return routedata.Values[_routeId].ToString().ToLower();
}
// Attribute Routing
if (routedata.Values.ContainsKey("MS_SubRoutes"))
{
var msSubRoutes = routedata.Values["MS_SubRoutes"] as IEnumerable<IHttpRouteData>;
if (msSubRoutes != null && msSubRoutes.Any())
{
var subRoute = msSubRoutes.FirstOrDefault();
if (subRoute != null && subRoute.Values.ContainsKey(_routeId))
{
return (string)subRoute.Values
.Where(x => x.Key.Equals(_routeId))
.Select(x => x.Value)
.Single();
}
}
}
return string.Empty;
}
}
API action:
[Route("api/{tenantId}/Values/Get")]
[HttpGet]
public IEnumerable<string> Get()
{
_testService.DoDatabaseWork();
return new string[] { "value1", "value2" };
}

you need to create a factory class for Dynamic picking of connection string.
It is the responsibility of that class to give correct connectionString based on the certain Parameter.

Using Session out of the Controller class

I am thinking to implement something like a static SessionHelper class where I would like to keep some data in Session.
But it seems like is impossible to use Session object out of the Controller class. Right?
Or may be I am wrong... I.e. is this link a solution ASP.NET MVC - How to access Session data in places other than Controller and Views
Let me know, please!
Anyway for now I cannot refer to Session object in that class which lives in Models folder.
public static class SessionHelper
{
public static bool ShowSuccessPopup
{
get
{
if (Session["ShowSuccessPopup"] == null)
{
Session["ShowSuccessPopup"] = false;
return false;
}
else
{
var result = (bool)Session["ShowSuccessPopup"].ToString();
return result;
}
}
set {Session["ShowSuccessPopup"] = value; }
}
}

The Session object is only set in the request-cycle, so anything outside the request-cycle won't have access to it (i.e. Controllers and Views are fine, but models no). If you need to work with the session in something outside of the request-cycle, then you must inject the Session object as a dependency. However, you're not going to be able to accomplish that with a static class. So you might instead try something like:
public class SessionHelper
{
private HttpSessionState session;
public SessionHelper (HttpSessionState session)
{
this.session = session;
}
public bool ShowSuccessPopup { ... }
}
Alternatively, you may be able to get by with merely injecting the session into your actual methods individually, but you wouldn't be able to continue using a property:
public static bool ShowSuccessPopup (HttpSessionState session)
{
// do something with session
}

Thanks to Chris Pratt!
Just like an alternative I am gonna share my approach.
public partial class BaseController : Controller
{
public SessionBox SessionBox;
protected override void OnActionExecuting(ActionExecutingContext filterContext)
{
SessionBox = new SessionBox(filterContext.HttpContext);
base.OnActionExecuting(filterContext);
}
}
public class SessionBox
{
private HttpContextBase context { get; set; }
public SessionBox(HttpContextBase context)
{
this.context = context;
}
public bool ShowSuccessPopup
{
get
{
if (context.Session["ShowSuccessPopup"] == null)
{
context.Session["ShowSuccessPopup"] = false;
return false;
}
else
{
var result = Convert.ToBoolean(context.Session["ShowSuccessPopup"].ToString());
return result;
}
}
set { context.Session["ShowSuccessPopup"] = value; }
}
}
Notice that you should inheritine Controller class on BaseController class
and later in the Controller class you can do like
if (SessionBox.ShowSuccessPopup)
{
SessionBox.ShowSuccessPopup = false;
Here are extra links that demonstrate difference between
http://msdn.microsoft.com/en-us/library/system.web.sessionstate.httpsessionstate.aspx
and
http://msdn.microsoft.com/en-us/library/system.web.httpcontextbase.aspx

Should I inject ServiceStack's ICacheManager?

I'm looking to implement a caching tier in our application and accidentally came across ServiceStack's ICacheManager.
ICacheManager.Resolve looks as though it's exactly what I'm after (try and get, if it's not in the cache then call the function to get and store it). All documentation I can find however is about using ICacheClient.
How I can wire up ICacheManager using AutoFac? I assume I need to wire up a client e.g.:
_builder.Register(c => new MemoryCacheClient())
.As<ICacheClient>();
But then I'm not sure what ICacheManager should resolve to.
Is this a good idea or am I abusing ServiceStack?
I've added a custom cache manager for the time being but it feels wrong for some reason:
public class CacheManager : ICacheManager
{
public CacheManager(ICacheClient cacheClient)
{
CacheClient = cacheClient;
}
public void Clear(IEnumerable<string> cacheKeys)
{
Clear(cacheKeys.ToArray());
}
public void Clear(params string[] cacheKeys)
{
CacheClient.ClearCaches(cacheKeys.ToArray());
}
public ICacheClient CacheClient { get; private set; }
public T Resolve<T>(string cacheKey, Func<T> createCacheFn) where T : class
{
return Resolve(cacheKey, new TimeSpan(0, 15, 0), createCacheFn);
}
public T Resolve<T>(string cacheKey, TimeSpan expireIn, Func<T> createCacheFn) where T : class
{
var cacheResult = CacheClient.Get<T>(cacheKey);
if (cacheResult != null)
return cacheResult;
var item = createCacheFn();
CacheClient.Set(cacheKey, item, expireIn);
return item;
}
}

Strongly typed metadata in MEF2 (System.Composition)

I'm using the System.Composition namespace from the MEF for web and Windows Store apps NuGet package in a new ASP.NET MVC4 project.
I've read that in MEF2 you no longer use Lazy<IExtension, IExtensionMetadata>, but now you must provide a concrete type for the metadata view (and possibly use ExportFactory<> instead of Lazy<> ?).
However, I can't find any examples of how this should all work - just a few mentions of using a concrete type instead of an interface.
I've tried a few things, but keep getting the following error - "Export metadata for 'AccountID' is missing and no default value was supplied".
My code...
Creating the container (in Global.asax or App_Start folder):
// Get assemblies that will be providing imports and exports
var assemblies = GetAssemblies();
// Get conventions that will be used to find imports and exports
var conventions = GetConventions();
var container = new ContainerConfiguration().WithAssemblies(assemblies, conventions).CreateContainer();
// Create and apply a MefControllerFactory so controllers can be composed
ControllerBuilder.Current.SetControllerFactory(new MefControllerFactory(container));
GetConventions() method:
private static ConventionBuilder GetConventions()
{
var conventionBuilder = new ConventionBuilder();
conventionBuilder.ForTypesDerivedFrom<IController>().Export();
conventionBuilder.ForTypesDerivedFrom<IExtension>().Export<IExtension>();
conventionBuilder.ForTypesMatching(t => t.Namespace != null && t.Namespace.EndsWith(".Parts")).Export().ExportInterfaces();
return conventionBuilder;
}
IExtension.cs:
public interface IExtension
{
void DoWork();
}
ExtensionMetadata.cs:
public class ExtensionMetadata
{
public int AccountID { get; set; }
}
ExtensionA.cs (same as ExtensionB.cs):
public void DoWork()
{
System.Diagnostics.Debug.WriteLine("ExtensionA doing work..");
}
ExtensionManager.cs:
public class ExtensionManager
{
private IEnumerable<ExportFactory<IExtension, ExtensionMetadata>> _extensions;
public ExtensionManager(IEnumerable<ExportFactory<IExtension, ExtensionMetadata>> extensions)
{
_extensions = extensions;
}
public void DoWork(int accountID)
{
foreach (var extension in _extensions)
{
if (extension.Metadata.AccountID == accountID)
{
extension.DoWork();
}
}
}
}
I think I'm missing something quite major here. Basically I want to lazily import all Extensions, check their metadata and if a condition is fulfilled have that extension do something.
Would really appreciate your feedback or any links to sample code / tutorials that cover my scenario.
Many thanks!

I think I've worked it out after reading this SO question.
I created a Metadata Attribute:
[MetadataAttribute]
public class ExtensionMetadataAttribute : ExportAttribute, IExtensionMetadata
{
public int AccountID { get; set; }
public ExtensionMetadataAttribute(int accountID) : base(typeof (IExtension))
{
AccountID = accountID;
}
}
Then modified ExtensionA.cs:
[ExtensionMetadata(1)]
public class ExtensionA : IExtension
{
public void DoWork()
{
System.Diagnostics.Debug.WriteLine("ExtensionA doing work..");
}
}
And now ExtensionManager.cs looks like this:
public class ExtensionManager : IExtensionManager
{
private readonly IEnumerable<ExportFactory<IExtension, ExtensionMetadata>> _extensions;
public ExtensionManager(IEnumerable<ExportFactory<IExtension, ExtensionMetadata>> extensions)
{
_extensions = extensions;
}
public void DoWork(int accountID)
{
foreach (var extension in _extensions)
{
if (extension.Metadata.AccountID == accountID)
{
using (var foo = extension.CreateExport())
{
foo.Value.DoWork();
}
}
}
}
}
This seems to do the trick, but I would still be interested in any feedback re best practices, performance issues etc.
Thanks!