---
title: Migrating Configuration | Microsoft Docs
author: ardalis
ms.author: riande
manager: wpickett
ms.date: 10/14/2016
ms.topic: article
ms.assetid: 8468d859-ff32-4a92-9e62-08c4a9e36594
ms.technology: aspnet
ms.prod: aspnet-core
uid: migration/configuration
---
# Migrating Configuration

By [Steve Smith](http://ardalis.com) and [Scott Addie](https://scottaddie.com)

In the previous article, we began [migrating an ASP.NET MVC project to ASP.NET Core MVC](mvc.md). In this article, we migrate configuration.

[View or download sample code](https://github.com/aspnet/Docs/tree/master/aspnetcore/migration/configuration/samples)

## Setup Configuration

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 should not be checked into source control. See [Configuration](../fundamentals/configuration.md) 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:

[!code-none[Main](configuration/samples/WebApp1/src/WebApp1/Startup.cs?range=11-21)]

Note that at this point, the *Startup.cs* file will not compile, as we still need to add the following `using` statement:

````csharp
using Microsoft.Extensions.Configuration;
````

Add an *appsettings.json* file to the root of the project using the appropriate item template:

![image](configuration/_static/add-appsettings-json.png)

## Migrate Configuration Settings from web.config

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:

[!code-json[Main](../migration/configuration/samples/WebApp1/src/WebApp1/appsettings.json?highlight=4)]


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.