An exception in C# is an unwanted or unexpected event that occurs at runtime. It affects the normal flow of the program. Common exceptions include invalid input, divide-by-zero operations, or accessing invalid array indices. C# provides a powerful exception-handling mechanism to successfully recover from these runtime issues and keep the program running smoothly.
Example: Divide By Zero Exception. This example shows the occurrence of the exception during divide by zero operation.
C# // C# program to illustrate the exception using System; class Geeks { static void Main(string[] args) { // Declaring two integer values int A = 12; int B = 0; // divide by zero error int C = A / B; Console.Write("Value of C is " + C); } } Output:
Unhandled Exception:
System.DivideByZeroException: Attempted to divide by zero.
at Geeks.Main (System.String[] args) [0x00005] in <78d30a8ae7274e28ac400780dfde8dc7>:0
[ERROR] FATAL UNHANDLED EXCEPTION: System.DivideByZeroException: Attempted to divide by zero.
at Geeks.Main (System.String[] args) [0x00005] in <78d30a8ae7274e28ac400780dfde8dc7>:0
Exception Handling in C#
C# provides try-catch and finally blocks to handle exceptions effectively.
Syntax:
try
{
// Code that may throw an exception
}
catch (ExceptionType ex)
{
// Handle the exception
}
finally
{
// Cleanup code (optional)
}
Example:
C# using System; class Geeks { static void Main() { try { int A = 10; int B = 0; // Attempting to divide by zero int res = A / B; Console.WriteLine("Result: " + res); } catch (DivideByZeroException ex) { Console.WriteLine("Error: " + ex.Message); } finally { Console.WriteLine("Execution completed."); } } } OutputError: Attempted to divide by zero. Execution completed.
C# Exception Hierarchy
In C#, all exceptions are derived from the base class Exception, which is further divided into two main categories:
- SystemException: This is the base class for exceptions generated by the Common Language Runtime (CLR) or system-related errors. Examples include DivideByZeroException and NullReferenceException.
- ApplicationException: This is the base class for exceptions related to the application. Developers can create custom exception types by inheriting from ApplicationException.
All exception classes in C# are ultimately derived from the Exception class, with SystemException containing standard system-related exceptions and ApplicationException allowing users to define their own specific exceptions. To know the difference between these, refer: System Level Exception Vs Application Level Exception in C#
Difference Between Errors and Exception
Features | Errors | Exceptions |
|---|
Definition | Errors are unexpected issues that may arise during computer program execution. | Exceptions are unexpected events that may arise during run-time. |
|---|
Handling | Errors cannot be handled by the Program. | Exceptions can be handled using try-catch mechanisms. |
|---|
Relationship | All Errors are exceptions. | All exceptions are not errors. |
|---|
C# Exception Classes
There are different kinds of exceptions which can be generated in C# program:
1. Divide By Zero exception: It occurs when the user attempts to divide by zero.
Example:
int result = 10 / 0; // Throws DivideByZeroException
2. NullReferenceException: Occurs when referencing a null object.
Example:
string str = null;
Console.WriteLine(str.Length); // Throws NullReferenceException
3. IndexOutOfRangeException: Thrown when accessing an invalid index in an array.
Example:
int[] arr = {1, 2, 3};
Console.WriteLine(arr[5]); // Throws IndexOutOfRangeException
4. OutOfMemoryException: Occurs when the program exceeds available memory.
5. StackOverflowException: Caused by infinite recursion.
Example:
void Recursive() => Recursive();
Recursive(); // Throws StackOverflowException
Properties of the Exception Class
The Exception class has many properties which help the user to get information about the exception during the exception.
- Data: This property helps to get the information about the arbitrary data which is held by the property in the key-value pairs.
- TargetSite: This property helps to get the name of the method where the exception will throw.
- Message: This property helps to provide the details about the main cause of the exception occurrence.
- HelpLink: This property helps to hold the URL for a particular exception.
- StackTrace: This property helps to provide the information about where the error occurred.
- InnerException: This property helps to provide the information about the series of exceptions that might have occurred.
Important Points:
- Use Specific Exceptions: Catch specific exceptions rather than a general Exception.
catch (DivideByZeroException ex) { /* Handle divide-by-zero */ }
- Avoid Empty Catch Blocks: Always log or handle exceptions meaningfully.
- Use Finally for Cleanup: Use the finally block to release resources like files or database connections.
- Do Not Overuse Exceptions: Use exceptions only for exceptional cases, not for control flow.
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