Common Types of Exceptions

Let’s dig into exceptions you can use in a try-catch in C#.

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📌 1. General Rule

In C#, you can catch any type that derives from System.Exception.

• The base class: Exception

• Specialized exceptions: ArgumentNullException, InvalidOperationException, etc.

You cannot catch things like string or int — only Exception objects.

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📌 2. Common Exception Types in C#

Here are the most frequently used ones:

General purpose

• Exception → base type (catches everything, but usually avoided by itself)

• SystemException → base for system-generated exceptions

Argument / parameter issues

• ArgumentException → invalid argument

• ArgumentNullException → argument is null when it shouldn’t be

• ArgumentOutOfRangeException → argument not in allowed range

Invalid operations

• InvalidOperationException → method call not valid for current state

• NotImplementedException → feature/method not yet implemented

• NotSupportedException → method/property not supported

I/O and external issues

• IOException → general I/O errors

• FileNotFoundException → file missing

• DirectoryNotFoundException → directory missing

• UnauthorizedAccessException → no permission

Collections / indexing

• IndexOutOfRangeException → index outside array bounds

• KeyNotFoundException → dictionary key doesn’t exist

Type conversion / casting

• InvalidCastException → invalid type conversion

• FormatException → string not in correct format

• OverflowException → arithmetic overflow

Concurrency / threading

• ThreadAbortException → thread forced to stop

• TaskCanceledException → async task canceled

• OperationCanceledException → operation canceled (with CancellationToken)

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📌 3. Example try-catch

try
{
    int[] numbers = { 1, 2, 3 };
    Console.WriteLine(numbers[5]); // throws IndexOutOfRangeException
}
catch (IndexOutOfRangeException ex)
{
    Console.WriteLine("Index was out of bounds: " + ex.Message);
}
catch (Exception ex)
{
    // fallback: catches all other exceptions
    Console.WriteLine("Something went wrong: " + ex.Message);
}

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📌 4. Best Practices

• Catch specific exceptions first, then Exception last as a fallback.

• Avoid catching Exception unless you need a global safety net.

• Use finally for cleanup (closing files, releasing resources).

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✅ In short: You can catch any class derived from System.Exception, and C# provides many built-in exceptions for common error scenarios.

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