How to create user defined exceptions in C#?

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

In the below example, the exception created is not a built-in exception.

TempIsZeroException

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

Example

 Live Demo

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);
      }
   }
}

Output

TempIsZeroException: Zero Temperature found