Is it a bad practice to have multiple classes in the same file?

Question

I used to have one class for one file. For example car.cs has the class car. But as I program more classes, I would like to add them to the same file. For

Answer 1

It can be bad from the perspective of future development and maintainability. It is much easier to remember where the Car class is if you have a Car.cs class. Where would you look for the Widget class if Widget.cs does not exist? Is it a car widget? Is it an engine widget? Oh maybe it's a bagel widget.