Error in access to Entity Framework data from WCF service in web and win form application?

Question

I am in the middle of big web application, I use Entity Framework as my data service, now we need some windows application to work with our data, so I want to give them a service with WCF

But when my client wants to get service some error is happened from my public property which I use for caching Entity Model

    public partial class DepositEntities : ObjectContext
    {
        public static DepositEntities Current
        {
            get
            {
                DepositEntities oc = 
                    HttpContext.Current.Items["ObjectContext"] as DepositEntities;

                if (oc == null)
                {
                    oc = new DepositEntities();
                    HttpContext.Current.Items["ObjectContext"] = oc;
                }

                return oc;
            }
        }
    }

I know the problem is from this line, after I debug my code

DepositEntities oc = System.Web.HttpContext.Current.Items["ObjectContext"] as DepositEntities;

When I change my Current property body to some thing like this

public static DepositEntities Current
{
   get
   {
      DepositEntities oc = new DepositEntities();
      return oc;
   }
}

everything is OK when I get data from services I have no problem

But everywhere I have join in my codes I have problem because It thinks there are different data source because of new DepositEntities();

Dear @LosFrijoles Exception is just Object reference not set to an instance of an object. for this line {DepositEntities oc = System.Web.HttpContext.Current.Items["ObjectContext"] as DepositEntities;} but this line works correctly in my whole project when I want to use WCF I get this error — Amir Fahmideh
– Amir Fahmideh, Commented Apr 14, 2012 at 6:58
The HttpContext only exists in the context of an ASP.NET web application. A Windows Forms application doesn't have an HttpContext so you cannot use it to cache data..... you need to check out some other means of caching that's not depedent on HttpContext. — marc_s
– marc_s, Commented Apr 14, 2012 at 7:12
You could check out the new .NET 4 System.Runtime.Caching namespace for general purpose caching that is available to all project types and doesn't depend on a HttpContext or anything — marc_s
– marc_s, Commented Apr 14, 2012 at 8:02

empi · Accepted Answer · 2012-04-14 06:53:38Z

1

You're most likely experiencing problems because WCF doesn't have HttpContext.Current. Read more about contexts in WCF - this question may be a good start: http://social.msdn.microsoft.com/Forums/en/wcf/thread/27896125-b61e-42bd-a1b0-e6da5c23e6fc.

I also think it would be better for you to manage lifetime of an ObjectContext with a DI Container (ie. Castle Windsor). Thanks to this, it won't be necessary to expose static property Current which is a problem for WCF service, unit tests, etc.

answered Apr 14, 2012 at 6:53

empi

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2 Comments

Amir Fahmideh Over a year ago

your answer seems correct but I couldn't find my solution it's a little complicated for me! can you tell me which session should I use to solve the problem !?

Amir Fahmideh Over a year ago

I change my way! I use Web Service in my client instead of using WCF

Olav Nybø · Accepted Answer · 2012-04-14 08:07:58Z

1

Check out "Hosting WCF Services in ASP.NET Compatibility Mode" in wcf service and ASP.NET. It explains how to get a valid HttpContext in a wcf service.

answered Apr 14, 2012 at 8:07

Olav Nybø

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