Custom exception classes in C Sharp (C#) - Mini Project: Build & Apply

Custom Exception Classes in C#

📖 Scenario: Imagine you are building a simple banking application. You want to handle errors clearly when someone tries to withdraw more money than they have in their account.

🎯 Goal: You will create a custom exception class called InsufficientFundsException to represent this specific error. Then, you will use this exception in a method that withdraws money from an account.

📋 What You'll Learn

Create a custom exception class named InsufficientFundsException that inherits from Exception.

Add a constructor to InsufficientFundsException that takes a string message and passes it to the base Exception class.

Create a variable balance of type decimal with the value 1000m.

Create a variable withdrawAmount of type decimal with the value 1500m.

Write an if statement to check if withdrawAmount is greater than balance and throw InsufficientFundsException with the message "Not enough money in the account.".

Write a try-catch block to catch InsufficientFundsException and print the exception message.

💡 Why This Matters

🌍 Real World

Custom exceptions help you handle specific errors in your programs clearly, like when a bank account has insufficient funds.

💼 Career

Understanding custom exceptions is important for writing robust, maintainable code in professional software development.

1

Create the custom exception class

Create a public class called InsufficientFundsException that inherits from Exception. Add a constructor that takes a string parameter message and passes it to the base Exception constructor using base(message).

C Sharp (C#)

// Your code here

Need a hint?

Remember to inherit from Exception and call the base constructor with the message.

2

Set up account balance and withdrawal amount

Create a decimal variable called balance and set it to 1000m. Create another decimal variable called withdrawAmount and set it to 1500m.

C Sharp (C#)

using System;

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

// Your code here

Need a hint?

Use decimal type and remember the m suffix for decimal literals.

3

Throw the custom exception when withdrawal is too large

Inside the Main method, write an if statement that checks if withdrawAmount is greater than balance. If true, throw a new InsufficientFundsException with the message "Not enough money in the account.".

C Sharp (C#)

using System;

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

class Program
{
    static void Main()
    {
        decimal balance = 1000m;
        decimal withdrawAmount = 1500m;

        // Your code here
    }
}

Need a hint?

Use throw new InsufficientFundsException("message") inside the if block.

4

Catch and display the custom exception message

Wrap the if statement inside a try block. Add a catch block that catches InsufficientFundsException as ex and prints ex.Message using Console.WriteLine.

C Sharp (C#)

using System;

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

class Program
{
    static void Main()
    {
        decimal balance = 1000m;
        decimal withdrawAmount = 1500m;

        // Your code here
    }
}

Need a hint?

Use try and catch (InsufficientFundsException ex) to handle the exception and print ex.Message.