When did the issue first time to occur? Have you made any modifications to the machine?
Please take the following steps to have a troubleshoot.
1.Open an administrator command line and run "dism/online/cleanup-image/restorehealth" or "sfc /scannow" to check the health of system files.
2.Perform a clean boot to verify whether this issue is caused by third party service.
How to perform a clean boot in Windows
https://support.microsoft.com/en-us/kb/929135
3.Open program and features control panel and right click the .Net Framework to fix it. We also could refer to the following link to have a fix of .Network Framework components.
NET Framework Cleanup Tool User's Guide
http://blogs.msdn.com/b/astebner/archive/2008/08/28/8904493.aspx