[View or download sample code](https://github.com/aspnet/Docs/tree/master/aspnetcore/migration/configuration/samples) ([how to download](xref:tutorials/index#how-to-download-a-sample))
ASP.NET Core no longer uses the *Global.asax* and *web.config* files that previous versions of ASP.NET utilized. In earlier versions of ASP.NET, application startup logic was placed in an `Application_StartUp` method within *Global.asax*. Later, in ASP.NET MVC, a *Startup.cs* file was included in the root of the project; and, it was called when the application started. ASP.NET Core has adopted this approach completely by placing all startup logic in the *Startup.cs* file.
The *web.config* file has also been replaced in ASP.NET Core. Configuration itself can now be configured, as part of the application startup procedure described in *Startup.cs*. Configuration can still utilize XML files, but typically ASP.NET Core projects will place configuration values in a JSON-formatted file, such as *appsettings.json*. ASP.NET Core's configuration system can also easily access environment variables, which can provide a more secure and robust location for environment-specific values. This is especially true for secrets like connection strings and API keys that shouldn't be checked into source control. See [Configuration](xref:fundamentals/configuration/index) to learn more about configuration in ASP.NET Core.
For this article, we are starting with the partially-migrated ASP.NET Core project from [the previous article](mvc.md). To setup configuration, add the following constructor and property to the *Startup.cs* file located in the root of the project:
Our ASP.NET MVC project included the required database connection string in *web.config*, in the `<connectionStrings>` element. In our ASP.NET Core project, we are going to store this information in the *appsettings.json* file. Open *appsettings.json*, and note that it already includes the following:
In the highlighted line depicted above, change the name of the database from **_CHANGE_ME** to the name of your database.
## Summary
ASP.NET Core places all startup logic for the application in a single file, in which the necessary services and dependencies can be defined and configured. It replaces the *web.config* file with a flexible configuration feature that can leverage a variety of file formats, such as JSON, as well as environment variables.
