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...