7.1 Try-Catch-Finally

Let’s go through try-catch-finally in C# — essential for exception handling. Also see Common Types of Exceptions.

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📌 1. What is Exception Handling?

• Exceptions are runtime errors that disrupt the normal flow of a program.

• Try-catch-finally allows you to handle errors gracefully instead of crashing the program.

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📌 2. Basic Syntax

try
{
    // Code that might throw an exception
}
catch (ExceptionType e)
{
    // Handle the exception
}
finally
{
    // Code that always runs, whether exception occurred or not
}

• try → Wrap code that might throw an exception

• catch → Handle the exception

• finally → Optional; runs always, e.g., for cleanup

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📌 3. Example: Simple try-catch

try
{
    int[] numbers = { 1, 2, 3 };
    Console.WriteLine(numbers[5]); // Index out of range
}
catch (IndexOutOfRangeException ex)
{
    Console.WriteLine("Error: " + ex.Message);
}

Output:

Error: Index was outside the bounds of the array.

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📌 4. Catching Multiple Exceptions

try
{
    int a = 10, b = 0;
    int result = a / b;
}
catch (DivideByZeroException ex)
{
    Console.WriteLine("Cannot divide by zero");
}
catch (Exception ex)
{
    Console.WriteLine("Some other error: " + ex.Message);
}

• Specific exceptions first, then general Exception

• Avoid catching general exceptions unless necessary

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📌 5. Finally Block

• Executes regardless of exception occurrence

• Useful for cleanup code (closing files, releasing resources)

try
{
    Console.WriteLine("Trying risky operation...");
}
catch (Exception ex)
{
    Console.WriteLine("Caught an exception: " + ex.Message);
}
finally
{
    Console.WriteLine("This always runs!");
}

Output:

Trying risky operation...
This always runs!

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📌 6. Throwing Exceptions

• You can manually throw exceptions using throw

void ValidateAge(int age)
{
    if (age < 0)
        throw new ArgumentException("Age cannot be negative");
}
 
try
{
    ValidateAge(-5);
}
catch (ArgumentException ex)
{
    Console.WriteLine(ex.Message);
}

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📌 7. Summary Table

Keyword	Purpose
try	Wrap code that might fail
catch	Handle specific exceptions
finally	Execute code regardless of exceptions
throw	Manually throw an exception

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✅ Tips:

• Always catch specific exceptions first

• Use finally to release resources

• Don’t overuse empty catch blocks — handle or log errors properly