Welcome to Microsoft community and we are happy to help you.
From your issue description, I understand dashost.exe and windows media player network services have increased the CPU usage to 99%.
Could you answer few questions to understand the issue well:
1. Are you using the network sharing feature in Windows Media Player?
2. Have you made any recent changes on your computer prior to the issue?
The “dashost.exe” is a process which automatically checks e-mail inbox and displays a notification if you get a new e-mail. It works on Windows 8 only if you have synchronized your mail account to mail app. So it is safe to kill the process.
The “windows media player network” service checks for the network computers or devices with which you want to share music. This service also indexes/updates the library that is being shared. So if you are not using network sharing feature in Windows media player, then you can kill this process.
If you are not using these services and still these are using the CPU, then follow these steps to change the type of start up to manual.
a. Press Windows key + R and type services.msc and press enter.
b. Double click on dashost.exe Service, and then change the service start up to Manual.
c. Double click on Windows Media Player Network Sharing Service, and then change the service start up to Manual.
These services are temporarily disabled now. So restart the computer and check for the CPU utility.
Hope it helps. For any Windows related queries you are always welcome to our community.