What is global.asax
Global.asax is an optional file which is used to handling higher level application events such as Application_Start, Application_End, Session_Start, Session_End etc. It is also popularly known as ASP.NET Application File. This file resides in the root directory of an ASP.NET-based application.
Global.asax contains a Class representing your application as a whole. At run time, this file is parsed and compiled into a dynamically generated .NET Framework class derived from the HttpApplication base class. You can deploy this file as an assembly in the \bin directory of an ASP.NET application. The Global.asax file itself is configured so that if a user requests the file, the request is rejected. External users cannot download or view the code written within it.
How to careet a Global.asax file
Global.asax file don't create normally; you need to add it by yourself.
How to ?
Your Global.asax file look like this
After that you need to add a class in your project.
Inherit the newly generated by System.Web.HttpApplication and copy all the method created Global.asax to Global.cs and also add an inherit attribute to the Global.asax file
Now your Global.asax will look like following: