Web Servers in Visual Studio for ASP.NET Web Projects

When you develop web projects in Visual Studio, you need a web server to test or run them. Visual Studio lets you test with different web servers, including IIS Express, Internet Information Services (IIS), or the built-in Visual Studio Development Server. You can use any of these servers with a file-based web application project. For a file-based web site project, you can use IIS Express or the built-in Visual Studio Development Server. This topic describes each of the web servers and how to select the server to test with.

The following table provides summary guidance for choosing a web server in Visual web Developer.

Web server

When to use

IIS Express

IIS Express is the default web server for web application projects in Visual Studio 2012 and is recommended for both web application projects and web site projects.

Visual Studio Development Server

Also known as Cassini, the Visual Studio Development Server is the legacy development web server. Cassini is the default web server when you open a file system folder as a web site project, but you can use IIS Express by choosing Use IIS Express from the Website menu.

IIS

Use IIS when you want to test your web application using the server environment that is closest to what the live site will run under, and it is practical for you to install and work with IIS on your development computer. For more information, see Disadvantages of Using IIS as a Development Server with Visual Studio later in this topic.

You can use IIS with web application projects, but not with web site projects.

IIS Express and the Visual Studio Development Server are designed to emulate IIS, but they are configured differently and may fail to reveal errors that can occur when you deploy to a production version of IIS. For more information, see Disadvantages of Using IIS Express or the Visual Studio Development Server later in this topic. If you use IIS Express or the Visual Studio Development Server, it is recommended that you test your application on a staging server that uses the target version of IIS before deploying it to a live site.

By default, Visual Studio 2012 uses IIS Express. For information about how to specify one of the alternative web servers, see How to: Specify the Web Server for Web Projects in Visual Studio.

IIS Express includes many of the features of IIS 7 web server without requiring you to install and manage IIS 7 on your computer. Because IIS Express is similar to IIS 7, it lets you transition web sites to IIS more smoothly than the built-in Visual Studio Development Server does.

IIS Express offers the following features:

  • It supports and enables the same extensibility model and Web.config file settings as IIS 7.

  • It does not require changes in your web application code.

  • It can be installed side-by-side with the full IIS web server as well as with the Visual Studio Development Server. You can choose a different web server for each project.

In corporate environments, IIS Express offers the following features:

  • It does not require an administrator account in order to run or debug applications.

  • It does not serve requests to a browser on another computer, making its approval easier in corporate environments.

  • It supports multiple developers on the same computer. Configuration files, settings, and web content are maintained on a per-user basis under the %systemdrive%\users\%username%\Documents folder.

  • It can be installed on versions of Windows that do not support IIS 7.

Tip Tip

Although IIS Express is derived from IIS and supports the core features of IIS, there are some differences between these servers. For more information, see IIS Express Overview, and Disadvantages of Using IIS Express or the Visual Studio Development Server later in this topic.

IIS Express is installed automatically when you install Visual Studio 2012. If you want to install it in Visual Studio 2010 (SP1 is required), you can use the Microsoft Web Platform Installer.

To install IIS Express

  1. In a browser, go to the installation page of the Microsoft.com/web site.

  2. Download the installer and then follow the steps to finish the installation.

IIS Express starts automatically when you run a project in Visual Studio, and it stops when you close the web site project or web application project in Visual Studio. When IIS Express is running, it displays an icon in the system tray, as shown in the following illustration.

IIS Express System Tray icon

The following table lists typical tasks for IIS Express and how to perform them.

Task

Steps

Display a list of all sites that are running on IIS Express

Right-click the IIS Express icon in the system tray, and then click Show All Applications.

View a web site directory location, configuration path, and .NET Framework version

Select the web site in the IIS Express window. The information will appear beneath the list of web sites.

Stop IIS Express

Right-click the tray icon and select Exit.

Note Note

In most cases, you do not have to shut down IIS Express manually. However, if you are using SQL Server Express, you might have to stop IIS Express manually before you can access a SQL Server Express .mdf file (for example, from SQL Server Management Studio).

If you do not want to use IIS Express or IIS as your web server, you can use the Visual Studio Development Server. The Visual Studio Development Server is a web server that runs locally on Windows operating systems. As with IIS Express, it is specifically built to run ASP.NET on the local computer. It will not serve requests to another computer. Additionally, it will not serve files that are outside the application scope. The Visual Studio Development Server is one way to test your web site or application locally before you publish it to a production server running IIS. However, if the production server that you will be publishing to is IIS 7 or a later version of IIS, IIS Express is a better choice because it is functionally closer to IIS 7.

The Visual Studio Development Server does not include all of the extra facilities of IIS. For example, like IIS Express, the Visual Studio Development Server does not support SMTP or FTP. If your web project involves sending email messages, you must have access to an IIS SMTP virtual server to test email.

Your options for configuring the Visual Studio Development Server are more limited compared to IIS Express. You can modify almost any IIS Express setting by editing configuration files, but you can only modify the settings for the Visual Studio Development Server that are available in the Visual Studio UI.

When you test a file-system web site using the Visual Studio Development Server, static files such as images and style sheets are subject to ASP.NET authorization. For example, Visual Studio Development Server will not serve static files in a file-system web site if they are in a folder that restricts anonymous users from accessing it and if you are testing the site as an anonymous user.

When you create a new file-based web site or web application project, a random port is selected for the project. For example, if you are testing a page called ExamplePage.aspx, when you run it on IIS Express or the Visual Studio Development Server, the URL of the page might be:

http://localhost:31544/ExamplePage.aspx

If you want to run IIS Express or the Visual Studio Development Server on a specific port, you can configure the server to do so. You might do this in these scenarios:

  • You have copied a web application project or web site project and you want to debug and work on both simultaneously. In that case you will have a port collision and will need to change the port number for one of the projects.

  • Your project includes a reference to a client project or web service that is bound to a specific port.

  • The code in your project listens to a specific port and you want to be able to test the application using IIS Express or the Visual Studio Development Server.

For more information, see How to: Specify a Port for the ASP.NET Development Server.

If your code references root-level resources such as CSS and JavaScript files without specifying that they are at the project root level, the application might work correctly when you test in Visual Studio but fail when you deploy it to IIS in production. Depending on how IIS is configured, a failure could happen in production because IIS may look for root level resources in the root of the IIS web site. For example, if you create a new MVC project in Visual Studio, you’ll find this line of code in the Views\Shared\_Layout.cshtml file:

@Styles.Render("~/Content/css")

The tilde (~) specifies that this resource is at the root level of the application. If you remove the tilde and run the application in Visual Studio with IIS Express or the Visual Studio Development Server, you see no change in the application appearance:

Normal MVC project template home page

But when you deploy to IIS (or select IIS as the development web server in Visual Studio), you see that CSS styling is lost because IIS can’t find the resource:

MVC project template home page with CSS missing

An important difference between the development servers in Visual Studio and IIS is the security context in which the servers run your ASP.NET pages. This difference can be a source of problems when you deploy a web site or web application to run on IIS.

When you run a page using IIS Express or the Visual Studio Development Server, the page runs in the context of your current user account. For example, if you are running as an administrator-level user, a page running in the Visual Studio Development Server will have administrator-level privileges. In contrast, in IIS 7, by default ASP.NET runs in an account that has limited privileges. For more information, see Application Pool Identities on the IIS.net web site.

If you are simply reading and running the code in ASP.NET pages, this difference is not very important. However, the different security contexts for the two web servers can affect your testing in several ways:

  • Database access   When you work with IIS Express or the Visual Studio Development Server, you can typically use Windows Integrated authentication to access SQL Server. However, when the same page runs in IIS, the page will be running in the context of the application pool identity. You can either use SQL Server authentication instead or add the application pool identity that the page runs under as a SQL Server login. For more information, see Accessing SQL Server from a Web Application, ASP.NET Security Architecture, and Application Pool Identities.

  • Code access security   If your page runs in medium trust (as most web hosting providers require), the page might run differently under the server in Visual Studio than it does in IIS.

  • Access to other resources that the page requires   This can include reading and writing files other than web pages, reading and writing the Windows registry, and so on.

The production web server for Microsoft operating systems is IIS, which can include a web server, File Transfer Protocol (FTP) server, Simple Mail Transfer Protocol (SMTP) virtual email server, and other facilities. In order to run IIS, you must be working with one of the versions of Windows that is listed in the following table.

Windows version

IIS version

Windows Server 2012

Windows 8, Windows 8 Pro

IIS 8

Windows Server 2008 R2

Windows 7 (Home Premium, Professional, Enterprise, and Ultimate editions)

IIS 7.5

Windows Server 2008

Windows Vista (Home Premium, Business, Enterprise, and Ultimate editions)

IIS 7.0

Windows Server 2003

Windows XP Professional x64

IIS 6.0

Windows XP Professional x32

IIS 5.1 (not recommended; use IIS Express instead. For more information, see Using IIS Express earlier in this topic.)

Working directly with IIS as your development web server lets you work in an environment closer to that of an IIS production web server. This can help you solve configuration problems before your project goes live. If you use IIS Express or the built-in Visual Studio Development Server, the transition to an IIS production web server might require you to perform extra configuration tasks because of the different security contexts between test and production servers.

Using IIS as a development server can require more setup and configuration tasks in order to work with Visual Studio than using IIS Express or the Visual Studio Development Server, including the following:

  • Both IIS and ASP.NET must be enabled in Windows, and ASP.NET must be registered with Windows. (Registration is a separate step if you installed the .NET Framework first, and then enabled IIS. For more information, see ASP.NET IIS Registration Tool (Aspnet_regiis.exe).)

  • You must run Visual Studio as an administrator in order to work with IIS.

In addition, it might be impractical for you to work with IIS if any of the following apply:

  • Your corporate workplace policy does not allow server roles like IIS to be enabled on developer computers.

  • Your corporate workplace policy does not allow developers to have administrator accounts on IIS.

  • You are developing ASP.NET web pages while working with a Home Edition of Windows, which does not support IIS.

  • You do not want to host a web server on your computer (for example, on your home network) for security reasons.

  • Your web project uses a SQL Server Express LocalDB database. For more information, see Using LocalDB with Full IIS on the SQL Server Express blog.

In these cases you can use either IIS Express or the Visual Studio Development Server.

In Windows XP, Windows Server 2003, and later versions of Windows, IIS is not installed by default.

If you have Windows Server 2012 or Windows 8 and you want to install IIS 8, see Installing IIS 8 on Windows Server 2012 on the IIS.net site, or Install IIS 8 and ASP.NET Modules on the TechNet site.

If you have Windows Server 2008 or Windows 7 and you want to install IIS 7, you can download the Web Platform Installer and use it to install the IIS 7 Recommended Configuration. This will enable both IIS and ASP.NET on your computer. For information about how to use IIS 7 with Visual Studio, see Running Web Applications on Windows Vista with IIS 7.0 and Visual Studio or Running Web Applications on Windows Server 2008 with IIS 7.0 and Visual Studio.

If you are using Windows Server 2003 and you want to install IIS 6, see Installing IIS (IIS 6.0) on the Microsoft Technet site. See also How To Enable Extensions Used by Visual Studio .NET in IIS 6.0 and How to: Create and Configure Local ASP.NET Web Sites in IIS 6.0.

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