I'm using EpiServer 7.9.1.0 verstion.

THis might not help you directly, but:

If you want to run code at site startup, you should use IInitializableModule or IConfigurableModule along with the InitializableModule attribute, this will ensure that EPiServer is done starting up before you run code, and will probably save you a lot of headache in the long run:

	[InitializableModule]
	[ModuleDependency(typeof(ServiceContainerInitialization), typeof(EPiServer.Web.InitializationModule))]
	public class Initializer : IConfigurableModule
	{
	}

You only need to add the attribute and interface implementations, EPiServer will scan all assemblies for this attribute and execute them in ModuleDependency order.

Your Global.asax.cs should look something like this:

public class EPiServerApplication : EPiServer.Global
    {
        protected void Application_Start()
        {
            //Tip: Want to call the EPiServer API on startup? Add an initialization module instead (Add -> New Item.. -> EPiServer -> Initialization Module)
        }
    }

You need to inherit from EPiServer.Global