Attaching to an existing ASP.NET Core process running inside a Windows Docker container

Quick Start

~5 minutes, provided you have Visual Studio 2017 and Docker tools installed

1 - Acquiring the .NET Core remote debugging tools

As of December 2017 it looks like this is the only way to acquire the .NET Core version of the Remote Debugging tools. Using the full version of the tools found at C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\Common7\IDE\Remote Debugger doesn't work - Visual Studio hangs when trying to attach to the .NET Core process.

• Ensure you have Visual Studio 2017 installed, along with Docker tools (Visual Studio Installer -> Modify -> Individual components -> Cloud, database, and server -> Container development tools)
• Create a new ASP.NET Core web application, and select "Enable Docker Support"
• Start the application through Visual Studio - this downloads the .NET Core remote debugging tools to C:\Users\<USER>\onecoremsvsmon

2 - Starting the application

• Clone this repository
• In the docker-compose.yml file, replace <USER> with your Windows username (and check the version number matches that of the .NET Core remote debugging tools downloaded in step 1)
• Build the DockerDebug solution through Visual Studio
• Ensure Windows containers are enabled (right-click system tray icon -> Switch to Windows containers)
• docker-compose up --force-recreate --build
• Visit http://172.18.0.2/api/test/get

Use the -d flag to run in detached mode, but be aware that this hides any startup errors

3 - Debugging

• Ensure Visual Studio has access through Windows Firewall (Windows Firewall -> Allow an app or feature through Windows Firewall -> scroll down to "Microsoft Visual Studio 2017")
• Open VS2017 in Administrator mode
• "Attach to Process" (ctrl+alt+p). Connection Type: Remote (no authentication), Connection Target: 172.18.0.2:4022 -> press enter
• Ensure "Show processes from all users" is enabled
• Find dotnet.exe and attach - when calling /api/test/get, a breakpoint in TestController.Get should now be hit

Useful commands

// view running containers including names/ids
docker container ls

// get IP address of container
docker inspect <container>

// attach to container via command line
docker exec -ti <container> powershell

// check running processes with powershell (should be running both msvsmon and dotnet)
Get-Process