Exception

An exception is an unexpected event that occurs during program execution. Examples include:

• Division by zero
• Opening a file that doesn’t exist
  When this happens, C# throws an exception, and if you “catch” it using try…catch,you can prevent your program from crashing.

Common Exception Types in C#

Exception Type	Meaning
DivideByZeroException	Division by zero
NullReferenceException	Trying to access a null object
IndexOutOfRangeException	Index is outside the array or list range
FormatException	Invalid type conversion (e.g., string → int)
FileNotFoundException	File not found
InvalidOperationException	Invalid operation in the current state

int a = 5;
int b = 0;

try
{
    int result = a / b;
    Console.WriteLine(result);
}
catch (DivideByZeroException ex)
{
    Console.WriteLine("You can't divide a number by zero!");
}

finally Block

The code inside finally always runs — whether or not an exception occurs

try
{
    int x = 10 / 0;
}
catch
{
    Console.WriteLine("An error occurred!");
}
finally
{
    Console.WriteLine("Program finished.");
}

Throwing Exceptions Manually

Sometimes you may want to throw an exception yourself to signal that something went wrong.

static void CheckAge(int age)
{
    if (age < 18)
        throw new Exception("❌ Age must be at least 18!");
    else
        Console.WriteLine("✅ Access granted.");
}

static void Main()
{
    try
    {
        CheckAge(15);
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }
}

Pro Tips

• Always catch specific exceptions instead of the general Exception.
• For large projects, define your custom exception classes.
• In production, log exceptions instead of displaying them directly.