What are the custom exceptions in C#?

Like any other programming language, in C#, you can easily create a user-defined exception. User-defined exception classes are derived from the Exception class. Custom exceptions are what we call user-defined exceptions.

In the below example, the exception created is not a built-in exception; it is a custom exception −

TempIsZeroException

You can try to run the following code to learn how to create a user-defined exception in C#.

Example

using System;

namespace Demo {
   class TestTemperature {
      static void Main(string[] args) {
         Temperature temp = new Temperature();
         try {
            temp.showTemp();
         } catch(TempIsZeroException e) {
            Console.WriteLine("TempIsZeroException: {0}", e.Message);
         }
         Console.ReadKey();
      }
   }
}

public class TempIsZeroException: Exception {
   public TempIsZeroException(string message): base(message) {}
}

public class Temperature {
   int temperature = 0;

   public void showTemp() {

      if(temperature == 0) {
         throw (new TempIsZeroException("Zero Temperature found"));
      } else {
         Console.WriteLine("Temperature: {0}", temperature);
      }
   }
}

This will produce the following output −

Output

TempIsZeroException: Zero Temperature found