Exception Handling in C# - Types, Examples, and Practical Guide

 // C# program to show how 
// Exceptions occur in a program
using System;
 
class ScholarHat { 
    static void Main(string[] args)
    {
        // An array of 4 indexes
        int[] arr = { 1, 2, 3, 4, 5 };
        // Displaying array values
        for (int i = 0; i < arr.Length; i++) {
            Console.WriteLine(arr[i]);
        } 
        // Try to access invalid index of array
        Console.WriteLine(arr[7]);
    }
}

 Exception

 try
{
    // Code that may throw an exception
}
catch (ExceptionType ex)
{
    // Code to handle the exception
    // 'ex' is the exception object that holds details about the error
}

 using System;

class Program
{
    static void Main()
    {
        try
        {
            // Code that may throw an exception
            int numerator = 10;
            int denominator = 0; // This will cause a DivideByZeroException
            int result = numerator / denominator;
            Console.WriteLine("Result: " + result);
        }
        catch (DivideByZeroException ex)
        {
            // Handling the exception
            Console.WriteLine("Error: Cannot divide by zero.");
            Console.WriteLine("Exception Message: " + ex.Message);
        }        
        // Additional code continues here if needed
        Console.WriteLine("Program continues even after the exception.");
    }
}

 Error: Cannot divide by zero.
Exception Message: Attempted to divide by zero.
Program continues even after the exception.

 try
{
    // Code that may throw an exception
}
catch (ExceptionType ex)
{
    // Code to handle the exception
    // 'ex' is the exception object that holds details about the error
}
finally
{
    // Code that will always execute, whether an exception is thrown or not
    // Typically used for resource cleanup
}

 using System;

class Program
{
    static void Main()
    {
        try
        {
            // Code that may throw an exception
            int numerator = 10;
            int denominator = 0; // This will cause a DivideByZeroException
            int result = numerator / denominator;
            Console.WriteLine("Result: " + result);
        }
        catch (DivideByZeroException ex)
        {
            // Handling the exception
            Console.WriteLine("Error: Cannot divide by zero.");
            Console.WriteLine("Exception Message: " + ex.Message);
        }
        finally
        {
            // This code will always run
            Console.WriteLine("Execution of the try-catch block is complete.");
        }
        
        Console.WriteLine("Program continues...");
    }
}

 Error: Cannot divide by zero.
Exception Message: Attempted to divide by zero.
Execution of the try-catch block is complete.
Program continues...

 try
{
    // Code that may throw multiple types of exceptions
}
catch (ExceptionType1 ex1)
{
    // Handle the first type of exception
}
catch (ExceptionType2 ex2)
{
    // Handle the second type of exception
}
catch (Exception ex)
{
    // Handle any other exceptions
}
finally
{
    // Code that will always execute, whether an exception occurred or not
}

 using System;

class Program
{
    static void Main()
    {
        try
        {
            // Code that may throw exceptions
            string input = "abc";
            int number = int.Parse(input); // This will throw FormatException
            int[] numbers = { 1, 2, 3 };
            Console.WriteLine(numbers[5]); // This will throw IndexOutOfRangeException
        }
        catch (FormatException ex)
        {
            Console.WriteLine("Error: Invalid format. Cannot convert string to integer.");
            Console.WriteLine("Exception Message: " + ex.Message);
        }
        catch (IndexOutOfRangeException ex)
        {
            Console.WriteLine("Error: Array index out of bounds.");
            Console.WriteLine("Exception Message: " + ex.Message);
        }
        catch (Exception ex)
        {
            // This will catch any other types of exceptions
            Console.WriteLine("An unexpected error occurred.");
            Console.WriteLine("Exception Message: " + ex.Message);
        }
        finally
        {
            // This block always runs, regardless of whether an exception occurred
            Console.WriteLine("Execution of the try-catch block is complete.");
        }
        Console.WriteLine("Program continues...");
    }
}

 Error: Invalid format. Cannot convert string to integer.
Exception Message: The input string 'abc' was not in a correct format.
Execution of the try-catch block is complete.
Program continues...

 try
{
    // Code that may throw exceptions
    throw new Exception("Custom exception message.");
}
catch (Exception ex)
{
    // Handle the exception
    Console.WriteLine("Caught an exception: " + ex.Message);
    throw; // Rethrow the caught exception
}
finally
{
    // Cleanup code that always runs
    Console.WriteLine("Execution of the try-catch block is complete.");
}

 using System;

class Program
{
    static void Main()
    {
        try
        {
            // Call a method that may throw an exception
            ThrowException();
        }
        catch (Exception ex)
        {
            // Handle the exception from the method
            Console.WriteLine("Caught an exception in Main: " + ex.Message);
        }
        finally
        {
            // This block always runs
            Console.WriteLine("Execution of the try-catch block is complete.");
        }

        Console.WriteLine("Program continues...");
    }
    static void ThrowException()
    {
        try
        {
            // Manually throw an exception
            throw new Exception("An error occurred in the try block.");
        }
        catch (Exception ex)
        {
            // Handle the exception
            Console.WriteLine("Caught an exception in ThrowException: " + ex.Message);
            throw; // Rethrow the exception for further handling
        }
        finally
        {
            // This block always runs
            Console.WriteLine("Execution of the ThrowException method is complete.");
        }
    }
}

 Caught an exception in ThrowException: An error occurred in the try block.
Execution of the ThrowException method is complete.
Caught an exception in Main: An error occurred in the try block.
Execution of the try-catch block is complete.
Program continues...

 using System;

// Define a custom exception class
public class InvalidAgeException : Exception
{
    public InvalidAgeException(string message) : base(message) { }
}

class Program
{
    static void Main()
    {
        try
        {
            int age = -1; // Let's say someone entered an invalid age
            if (age < 0)
            {
                throw new InvalidAgeException("Age cannot be negative."); // Throwing the custom exception
            }
            Console.WriteLine("Your age is: " + age);
        }
        catch (InvalidAgeException ex)
        {
            // Catching and handling the custom exception
            Console.WriteLine("Caught an invalid age exception: " + ex.Message);
        }

        Console.WriteLine("Program continues..."); // Program keeps running
    }
} 

 Caught an invalid age exception: Age cannot be negative.
Program continues...