At times, you see that line numbers are not coming up in Visual Studio. In fact, this is a setting which can be customized as per your need. You can even enable or disable this feature as per the file types.
Go to Tools –> Options and select Text Editor and enable line numbers as shown below.
You can see that it is also showing all other languages. You can customize a lot of other settings related to editors. You can also explore them. :)