Rider: a lot of red unresolved code in the solution

Problem

Possible Symptoms

• Some projects fail to load (Load failed link appears near the project name).
• Some projects have errors (Has errors link appears near the project name).
• Yellow warning triangles in Dependencies > Assemblies or no references at all in Dependencies > Assemblies.
• A lot of red code (unresolved symbols, often in using directives).

Cause

The issue is most likely caused by an incorrect MSBuild version.

Resolution

Follow these steps to troubleshoot and resolve the issue:

1. Open the Problems View tool window and check the Toolset, Environment tab. It may suggest possible solutions to the issue.
2. Go to File | Settings | Build, Execution, Deployment | Toolset and Build, and try changing the MSBuild version.
3. If the issue persists, enable design-time build logging via Help > Diagnostic Tools > Enable Design Time Build Logging.
4. Reproduce the issue.
5. Collect logs using Help > Collect Logs.