C# Exception Handling Guide

What is Exception Handling?

Exception handling is like a safety net for your code. It's a way to deal with unexpected errors that might happen when your program is running.

Real-life Analogy

Think of exception handling like wearing a helmet while biking. You hope you won't fall, but if you do, the helmet protects you from serious injury.

Why We Need It:

Prevents program crashes
Provides helpful error messages
Allows graceful recovery from errors
Helps with debugging

Basic Try-Catch Structure

try
{
    // Code that might cause an error
    int result = Divide(10, 0);
}
catch (Exception ex)
{
    // What to do if an error happens
    Console.WriteLine($"Error: {ex.Message}");
}

Common Exception Types

Exception Type	When It Occurs
DivideByZeroException	Dividing a number by zero
NullReferenceException	Trying to use a null object
FileNotFoundException	Trying to open a file that doesn't exist
IndexOutOfRangeException	Accessing an array element that doesn't exist
FormatException	Invalid format when converting data

Example of Handling Different Exceptions

try
{
    int[] numbers = {1, 2, 3};
    Console.WriteLine(numbers[5]); // This will cause an error
}
catch (IndexOutOfRangeException ex)
{
    Console.WriteLine("You tried to access an invalid array index");
}
catch (Exception ex)
{
    Console.WriteLine($"Some other error occurred: {ex.Message}");
}

Finally Block

The finally block contains code that will always run, whether an exception occurs or not. It's perfect for cleanup tasks.

try
{
    // Code that might cause an error
    File.OpenRead("nonexistent.txt");
}
catch (FileNotFoundException ex)
{
    Console.WriteLine("File not found: " + ex.Message);
}
finally
{
    // This code always runs
    Console.WriteLine("Cleanup completed");
}

Real-life Analogy

Think of the finally block like cleaning up after cooking. Whether your meal was successful or you burned it, you still need to wash the dishes and put things away.

Throwing Exceptions

You can also create your own exceptions when something goes wrong in your code.

public int Divide(int a, int b)
{
    if (b == 0)
    {
        throw new DivideByZeroException("Cannot divide by zero");
    }
    return a / b;
}

// Using the method
try
{
    int result = Divide(10, 0);
}
catch (DivideByZeroException ex)
{
    Console.WriteLine(ex.Message);
}

When to Throw Exceptions:

When method receives invalid arguments
When an operation cannot be completed
When an object is in an invalid state

Do	Don't
Use specific exception types	Use empty catch blocks
Provide meaningful error messages	Catch exceptions you can't handle
Clean up resources in finally blocks	Use exceptions for normal flow control
Log exceptions for debugging	Throw exceptions for minor issues

C# Exception Handling

What is Exception Handling?

Real-life Analogy

Why We Need It:

Basic Try-Catch Structure

Common Exception Types

Example of Handling Different Exceptions

Finally Block

Real-life Analogy

Throwing Exceptions

When to Throw Exceptions:

Best Practices

Do's and Don'ts

Example of Good Exception Handling