Custom Exceptions in C#

In this blog, we will learn about Custom Exceptions in C#

Introduction

 

Here we will see how to handle a Custom Exception class with both interfaces (Exception, ApplicationException) using C#.

 
Let’s develop a simple C# console application to show a Custom Exception class.

Getting Started

 

In ASP.NET 5 we can create console applications. First, open Visual Studio 2015 and create a new console application using File-> New-> Project.

 

 

 

Now we will select the ASP.NET 5 Console Application and click on the OK button.

 

 

 

We need to include the following references in our application:

using System;
using System.Text.RegularExpressions;
using System.Collections.Generic;

In the main method, I have created 3 classes and 1 method

1. Student – To define class members.
2. InvalidStudentNameException = Initialize with exception interface in the class.
3. InvalidStudentIDException = Initialize with Application Exception interface in the class.
4. ValidateStudent – Validate the value in this method.

try
{
    Student newStudent = new Student();
    Console.WriteLine("Enter the student id, Should be numeric : ");
    newStudent.StudentID = Convert.ToString(Console.ReadLine().Trim());
    Console.WriteLine("\n");

    Console.WriteLine("Enter the student name, Should be alphabetic : ");
    newStudent.StudentName = Convert.ToString(Console.ReadLine().Trim());
    Console.WriteLine("\n");

    ValidateStudent(newStudent);

}
catch (Exception ex)
{
    Console.WriteLine("Error:" + ex.Message);
}

Console.ReadKey();
}

Initialize the class

 

The first-class definition for the Student is given below:

class Student
{
    public string StudentID { get; set; }
    public string StudentName { get; set; }
}


The second-class definition for the InvalidStudentNameException is given below

[Serializable]
class InvalidStudentNameException : Exception
{
    public InvalidStudentNameException(string name) : base(String.Format("Invalid Student Name: {0}", name))
    {
    }
}

The third-class definition for the InvalidStudentIDException is given below:

[Serializable]
    class InvalidStudentIDException : ApplicationException
    {
        public InvalidStudentIDException(string Id) : base(String.Format("Invalid Student Id: {0}", Id))
        {
        }
    }

 

Initialize the Method

 

The method definition for ValidateStudent() is given below:

private static void ValidateStudent(Student std)
{
    if (!Regex.IsMatch(std.StudentID, "^[0-9]*$"))
    {
        Console.WriteLine(new InvalidStudentIDException(std.StudentID).Message);
    }

    if (!Regex.IsMatch(std.StudentName, "^[a-zA-Z]+$"))
    {
        Console.WriteLine(new InvalidStudentNameException(std.StudentName).Message);
    }
}

Click on F5, execute the project and follow the console window. The output will be:

 

 

 

I hope this article is helpful for the design of a Custom Exception in both interfaces. Thanks for reading this article!

 

Happy Coding...