Go to internet information service and change the version of project. the full steps are given below:
Step 1: Open start menu –> run
Step 2: Type inetmgr on run window
step 3: Internet information Service window is open now
Step 4: Go to your project under Website –> Default website
step 5: Right click on project –> select properties
Step 6: Go to ASP.NET tab
step 7: In the ASP.NET version dropdown you can select the appropriate version of .net for your project.