Issue
An unhandled exception (or error case) was encountered in one of .NET for Android's MSBuild tasks.
解决方案
如果在正常情况下收到此警告，请考虑提交 bug 。
Specific scenario 1
Issue
An exception was thrown and logged, including a C# exception stack trace showing where the failure occurred.
解决方案
Likely, the only option is to submit a bug.
Specific scenario 2
Issue
You are using a $(TargetFrameworkVersion) which cannot be mapped to a valid android api-level.
解决方案
检查是否已选择有效 $(TargetFrameworkVersion) 且所需的 Android API 级别安装在 $（AndroidSdkDirectory）\platforms 中。