When setting up multiple ASP.NET sites under a single domain with subdirectory paths (like example.com/community), many administrators confuse virtual directories with applications. The key distinction:

• Virtual directories simply map physical paths to URL paths
• Applications run in isolated execution contexts with their own config

Here's how to properly configure this in IIS Manager:

1. Create parent site (example.com):
   - Physical path: C:\sites\main
   - Binding: example.com:80

2. For /community sub-site:
   - Right-click parent site → Add Application
   - Alias: community
   - Physical path: C:\sites\community
   - Application pool: (create new or select existing)

3. For /labs sub-site:
   - Repeat above with appropriate paths
   - Each gets independent web.config

To prevent conflicts between sites:

• Separate application pools for isolation (memory leaks/crashes won't affect parent)
• In each application's web.config:

<location path="." inheritInChildApplications="false">
  <system.web>
    <compilation debug="true" targetFramework="4.7.2" />
  </system.web>
</location>

Sample parent site structure:

C:\sites\
├── main\          (parent site)
│   ├── default.aspx
│   └── web.config
├── community\     (sub-application)
│   ├── default.aspx
│   └── web.config
└── labs\          (sub-application)
    ├── default.aspx
    └── web.config

Each web.config can have completely different settings while sharing the same domain and port.

• HTTP Error 500.19: Verify physical paths and NTFS permissions
• Configuration inheritance: Use <clear/> in child web.config if needed
• Authentication conflicts: Set inheritInChildApplications="false" for auth sections

When deploying multiple ASP.NET applications under a single domain in IIS7, the standard approach of creating separate sites with different ports or host headers isn't always ideal. What we need is a way to:

• Maintain a primary site at the root domain (www.example.com)
• Host completely independent applications in subdirectories (/community, /labs)
• Use a single port (80) for all sites
• Keep each application isolated with its own configuration

The key is using Virtual Applications rather than Virtual Directories. Here's how they differ:

<!-- Example applicationHost.config snippet -->
<application path="/community" applicationPool="CommunityAppPool">
  <virtualDirectory path="/" physicalPath="C:\sites\community" />
</application>
<application path="/labs" applicationPool="LabsAppPool">
  <virtualDirectory path="/" physicalPath="C:\sites\labs" />
</application>

1. Create your main site first (right-click Sites > Add Web Site)

2. For each subdirectory application:

- Right-click the main site > Add Application
- Alias: "community" (this becomes your URL path)
- Application pool: Create or select dedicated pool
- Physical path: Point to the application's root folder

Application Pool Isolation: Always use separate application pools for each virtual application to prevent configuration conflicts.

Authentication Inheritance: By default, sub-applications inherit authentication settings. To override:

<location path="community" allowOverride="false">
  <system.webServer>
    <security>
      <authentication>
        <anonymousAuthentication enabled="true" />
      </authentication>
    </security>
  </system.webServer>
</location>

To make sub-applications appear as root paths in their own context:

<rewrite>
  <rules>
    <rule name="Community Rewrite" stopProcessing="true">
      <match url="^community/(.*)" />
      <action type="Rewrite" url="{R:1}" />
    </rule>
  </rules>
</rewrite>

HTTP 500.19 Errors: Typically occur when the sub-application's web.config improperly inherits or conflicts with parent settings. Solution:

<clear />  <!-- In authentication sections -->
<remove name="ModuleName" />  <!-- For module conflicts -->

Session Conflicts: Ensure each application uses unique machineKey values in web.config when sharing the same domain.