c# - Is it "bad" to use try-catch for flow control in .NET?

Question

I just found in a project:

try
{
    myLabel.Text = school.SchoolName;
}
catch
{
    myPanel.Visible = false;
}

I want to talk to the developer than wrote this, saying that incurring the null exception (because school might theoretically be null, not myLabel) would virtually make the computer beep three times and sleep for two seconds. However, I wonder if I'm misremembering the rule about that. Obviously, this isn't the intended use for try/catch, but is this bad because it defies intention, or bad because of performance considerations? I feel like it's just bad, but I want to say more than "that's really bad".

Answer 1

You should not use exceptions for control flow simply because it is bad design. It doesn't make sense. Exceptions are for exceptional cases, not for normal flow. Performance probably won't be an issue in this situation because for most modern applications on modern hardware, you could throw exceptions all day long and the user wouldn't notice a performance hit. However, if this is a high performance application processing a lot of data or doing a lot of some sort of work, then yes, performance would be a concern.