How to create user defined Exception ?

Abhishek Srivasatava 1634 19 Sep 2016

Abhishek Srivasatava

Employee

1 Answers

Abhishek Srivasatava 19 Sep 2016

Following is the step we need to follow to create user defined exception:

Step 1 : Create a derived class and inherit it with exception base class

example // class universalerror : Exception

Step 2 : create a constructor for the derived class and pass the string parameter

syntax : public universalerror(String message) : base(message) // what is the need of this line. I will explain you through program in 3 step.

step 3 : Declaration for the exception is made by the above two steps. Now we need to define the exception.

Create another class under the new class create a function put the condition for this variable

example :
class testexp
    {
        public int a;
 
        public void strgerr()
        {
            if (a== 0)
            {
               
throw (new universalerror("Error, please check")); // Base Message when exception is meet 
            
            }
            else
            {
                Console.WriteLine("Universal error is not there");// Base Message when exception is not meet.            
            }
        }
    }

Base message in step : 2 is to give the add on for the string message (which may define in the main program or in executing function).

step 4 : Now create another class , create the object for the defining class of the exception.

Step 5: now with the help of three keyword Try & Catch

class Program
    {
 
        static void Main(string[] args)
        {
           
           
testexp exp1 = new testexp();
            try
            {
              exp1.a = 25;
               
             exp1.strgerr();
            }
            catch (universalerror e)
            { 
                 Console.WriteLine("universal error {0}", e.Message);
            }
           
Console.ReadLine();
        }
    }
}

Under Try : we perform all operations.

Under Catch : if an exception is met , then we can give the add on to the defined message .

Here is the complete program for the above step:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication3
{
    classuniversalerror : Exception
    {
        public universalerror(String message) : base(message)
        {
        }
    }
    class testexp
    {
        public int a;
        public void strgerr()
        {
            if (a== 0)
            { 
              throw (new universalerror("Error, please check"));          
            }
            else
            {  
             Console.WriteLine("Universal error is not there");       
            }
        }
    }
    class Program
    {
        static void Main(string[] args)
        {       
           
            testexp exp1 = new testexp();
            try
            {
               
            exp1.a = 0; //for exception is met.

            //exp1.a=25; for exception is not met.
               
            exp1.strgerr();         
            }
            catch (universalerror e)
            {
            Console.WriteLine( "universal error {0}",e.Message);
            }
           
            Console.ReadLine();
        }
    }
}

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How to create user defined Exception ?

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