Publish ASP.NET Core to IIS

1. How IIS + ASP.NET Core Actually Works

Old ASP.NET: IIS loaded your DLL inside w3wp.exe.
ASP.NET Core: IIS uses AspNetCoreModuleV2 as a reverse proxy. Your app runs in dotnet.exe. IIS just passes traffic.

2. Publish in 4 Steps - No Fails

Step 1: Install Hosting Bundle
Server → Download ".NET Core Hosting Bundle" for your version. This installs runtime + AspNetCoreModuleV2. Reboot IIS: iisreset.

Step 2: Publish from VS
Right-click project → Publish → Folder → Target: Framework-dependent, Deployment: win-x64. This creates web.config automatically.

Step 3: IIS Setup
1. Copy publish folder to C:\inetpub\wwwroot\MyApp
2. IIS → Add Website → Physical path = your folder.
3. Application Pool →.NET CLR Version = No Managed Code. Yes, really.

Step 4: Fix Permissions
Folder → Security → Give IIS AppPool\MyApp Read+Execute. Give IUSR Read.
If writing files/logs: AppPool needs Write on that folder.

1. The Interview Theory: InProcess vs OutOfProcess

InProcess: <AspNetCoreHostingModel>InProcess</AspNetCoreHostingModel> in.csproj. Default. IIS loads your app inside w3wp.exe. Faster. 1 app pool = 1 app. If app crashes, pool dies.

OutOfProcess: IIS starts dotnet MyApp.dll. IIS forwards via named pipe. Slower. More stable. 1 app pool can host many apps.

Staff Rule: Use InProcess unless you need multiple apps per pool or running.NET Core 2.1.

2. The #1 Interview Question: "Debug 500.30"

Your Answer: "500.30 = ANCM failed to start app. Checklist: 1. Check Event Viewer for exact exception. 2. Enable stdout logs: edit web.config, set stdoutLogEnabled=true, stdoutLogFile=.\logs\stdout. Create logs folder. 3. Run dotnet MyApp.dll manually in publish folder. If it crashes there, it's code/config, not IIS. 4. Check dotnet --list-runtimes. App needs exact or compatible runtime. 5. Check connection string. Dev DB won't work from prod server."

3. web.config - The File That Runs Your App

IIS doesn't read appsettings.json. It reads web.config to start your app.

<aspNetCore processPath="dotnet"
            arguments=".\MyApp.dll"
            stdoutLogEnabled="false"
            stdoutLogFile=".\logs\stdout"
            hostingModel="InProcess" />

Key: processPath="dotnet" = framework-dependent. If self-contained publish, path = .\MyApp.exe.

4. Environment & Connection Strings

Theory: Don't put prod secrets in appsettings.json in publish folder. Use environment variables.

IIS Way: IIS → Configuration Editor → system.webServer/aspNetCore → environmentVariables. Add ASPNETCORE_ENVIRONMENT = Production.

Code: builder.Configuration.AddEnvironmentVariables() reads them. Connection string: ConnectionStrings__Default = Server=...;

5. Zero-Downtime Deploy Strategy