53 lines
3.4 KiB
Markdown
53 lines
3.4 KiB
Markdown
---
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title: Migrating Configuration
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author: ardalis
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description:
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manager: wpickett
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ms.author: riande
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ms.date: 10/14/2016
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ms.prod: asp.net-core
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ms.technology: aspnet
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ms.topic: article
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uid: migration/configuration
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---
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# Migrating Configuration
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By [Steve Smith](https://ardalis.com/) and [Scott Addie](https://scottaddie.com)
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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.
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[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))
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## Setup Configuration
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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.
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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](xref:security/app-secrets) 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.
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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:
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[!code-csharp[](configuration/samples/WebApp1/src/WebApp1/Startup.cs?range=11-21)]
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Note that at this point, the *Startup.cs* file won't compile, as we still need to add the following `using` statement:
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```csharp
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using Microsoft.Extensions.Configuration;
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```
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Add an *appsettings.json* file to the root of the project using the appropriate item template:
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## Migrate Configuration Settings from web.config
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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:
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[!code-json[](../migration/configuration/samples/WebApp1/src/WebApp1/appsettings.json?highlight=4)]
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In the highlighted line depicted above, change the name of the database from **_CHANGE_ME** to the name of your database.
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## Summary
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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.
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