Switching between debug and release mode multiple times is not handled correctly

Unity: Mono

2023.1.X

2022.2.X

2021.3.X

2022.1.X

2020.3.X

Fixed issue where the Unity runtime would refuse C# debugger connections after alternating between release & debug optimizations multiple times.

This issue has already been fixed previously in 2020.3

Reproduction steps:

Open the user’s attached project
Open the “SampleScene” Scene
Open file Test.cs in Visual Studio
Put a breakpoint in the method OnValidate
Hit F5 to start the debugger, and wait for debugging session to start
Unity asks for enabling debugging, click "Enable debugging for this session"
Hit F5 to continue
Back in Unity, edit member "Value" of object Test to trigger again the debug breakpoint
Close the debugging session in Visual Studio ( Shift F5 )
Back in Unity, click the debug icon in the lower right corner of the Main Window, which pops up a dialog about debugging
Click on "Switch to release mode"
Try to start debugging session directly from Visual Studio (F5)

Expected result: Debugging session starts
Actual result: Debugging session does not start

Reproducible with: 2020.3.40f1, 2021.3.11f1 2022.1.19f1. 2022.2.0b9, 2023.1.0a13

Reproduced on: Windows 10 Pro 21H2,

Notes:

In Visual Studio, click on "Debug/Attach Unity Debugger", and notice that now we have 3 different debugger instances displayed
Note that this is not related to Visual Studio 2022, the same issue reproduces with Visual Studio 2019
If reload assemblies never load, delete the projects library and try again