C# Exceptions

In C#, an exception is an unexpected event that occurs during the execution of a program, which disrupts the normal flow of the program. Exceptions can occur due to various reasons such as invalid input, division by zero, file not found, or network issues.

Example:

int a = 5, b = 0; int result = a / b; // Throws DivideByZeroException Console.WriteLine(result); 

Types of Exceptions in C#

Exceptions in C# can be broadly classified into two types:

1. System Exceptions

• These are exceptions thrown by the CLR (Common Language Runtime).
• Examples: DivideByZeroException, NullReferenceException, IndexOutOfRangeException

2. Application Exceptions

• These are custom exceptions defined by the user to indicate application-specific errors.
• Derived from the ApplicationException class.

Examples of Common Exceptions

1. DivideByZeroException

Occurs when a number is divided by zero.

int a = 10, b = 0; int result = a / b; // Throws DivideByZeroException 

2. NullReferenceException

Occurs when trying to access a member of an object that is null.

string str = null; int len = str.Length; // Throws NullReferenceException 

3. IndexOutOfRangeException

Occurs when accessing an array element outside its valid range (size of array).

int[] arr = { 1, 2, 3 }; int x = arr[5]; // Throws IndexOutOfRangeException 

4. Custom Application Exception

You can define your own exceptions by extending ApplicationException.

using System; class InvalidAgeException : ApplicationException {  public InvalidAgeException(string message) : base(message) { } } class Program {  static void CheckAge(int age)  {  if (age < 18)  throw new InvalidAgeException("Age must be 18 or older.");  } } 

Properties of the Exception Class

The Exception class in C# provides several properties to retrieve detailed information about an exception when it occurs:

• Data: Holds arbitrary user-defined information in key-value pairs related to the exception.
• TargetSite: Returns the method where the exception was thrown.
• Message: Provides a description of the cause of the exception.
• HelpLink: Stores a URL pointing to a help file or documentation for the exception.
• StackTrace: Provides the sequence of method calls that led to the exception, helping to locate where the error occurred.
• InnerException: Contains another exception that caused the current exception, allowing tracking of exception chains.

Exception vs Error

Key Points

• Exceptions are runtime anomalies, not compile-time errors.
• System exceptions are thrown by the CLR, application exceptions are user-defined.
• Exception properties provide detailed information about the cause and context of the error.
• Unlike errors, exceptions can often be anticipated and managed.