Powershell: Method not found: ‘System.Threading.Tasks.Task System.Threading.Tasks.Task.Run(System.Action)’
when you tried to start powershell and the window opens and closes immediately.
Open a cmd and start powershell by calling powershell.exe
C:\> powershell.exe Windows PowerShell terminated with the following error: Could not load type 'System.Management.Automation.Runspaces.EarlyStartup' from assembly 'System.Management.Automation, Version=18.104.22.168...'. or "System.Management.Automation.Tracing.PSEtwLog' threw an exception"
This error occures if Windows Management Framework 5.1 is installed and not the previous Verions 4 or 5.0 on which it depends or .NET Framework is corrupt.
Uninstall Windows Management Versions 5.1 and 5.0 and install install the latest 4.xx Version of .NET Framework, then Windows Management Version 4, 5.0 and 5.1.