Hi Abdusalam,
Based on my experience, I think there is a bad project reference string in ?D:\mysolution.sln?. If you don?t have many projects in your solution. I think you can migrate the projects one by one by double clicking the project files (not sln file). Then add the migrated projects in a blank solution file as a workaround.
Sincerely,
Benson Yu
Microsoft Online Community Support
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