C# Exception: C# Exception handling best practices

Last updated on December 15th, 2023 at 09:38 pm

An exception is defined as an event that occurs during the program execution that is unexpected by the program code. Exception handling is important because it handles an unwanted exception so that your program code does not crash and remains meaningful to the user.

In this article, we will discuss the exception types and exception handling in C# using try, catch, and finally blocks.

What is an Exception in C#?

An exception is a runtime error that interrupts the normal flow of a program. In other words, an exception is an abnormal condition that causes a running program to terminate. If the exception is not handled, the application may crash.

C# Exception Classes

The .NET framework provides a number of built-in classes for dealing with common exceptions that can result in program termination.

Following is the list of a few important exception classes available in C#, such as:

• NullReferenceException
• ArgumentException
• FormatException
• FileNotFoundException
• IndexOutOfRangeException
• ArithmeticException

What Is Exception Handling in C#?

C# Exception Handling is a process to handle runtime errors. Exception handling ensures that the flow of the program shouldn’t break when an exception occurs.

Exceptions in the program can occur because of multiple reasons such as the wrong input, coding errors made by the programmer, system errors, or other unpredicted things.
In C#, the exception handling is done by implementing the keywords try, catch, finally, and throw.

The System.Exception class is the base class of all exceptions in C#.

Exceptions in C# allow an application to transfer control from one part of the code to another. When an exception is thrown in an application, the current code execution is interrupted and returned to a parent try-catch block.

Try Catch Finally in C#

C# exception handling is done using the following built-in keywords:

• try
• catch
• finally, and
• throw

Syntax

Following is the syntax to define try/catch and finally blocks.

 // try block
try
{
 // statements that may cause exception
}
 // catch block
catch (Exception ex)
{
 // exception handling
 // write logs
}
 // finally block
finally
{  
 // statements to be executed
 // Instructions to clean up resources
 // or dispose objects
}

In the above code syntax, the try block is used to encapsulate areas of code that may cause exceptions. Catch blocks, on the other hand, are used to handle different types of exceptions.

Example: Exception handling using try-catch block

In the following example, we will try to divide a number by zero.

The System.DivideByZeroException is a class that indicates that a statement attempted to divide a dividend with zero.

DivideByZeroException derives from the ArithmeticException that doesn’t have a catch block explicitly defined to handle the DivideByZeroException errors.

 static void Main(string[] args)
        {
            try
            {
                int number = 10;
                int div = 0;
                int result;
                result = (number / div); // Exception will occur
                Console.WriteLine($"The result of {number}/{div} is : {result}");
            }
            catch(DivideByZeroException exception)
            {
                Console.WriteLine($"Exception: {exception.Message}");
            }
            catch (Exception exception)
            {
                Console.WriteLine($"Exception: {exception.Message}");
            }

            finally 
            {
                Console.WriteLine("Enter finally block ");
            }

            Console.ReadKey();
        }

throw keyword in C#

The throw keyword in C # can be used to throw any kind of exception when needed.

The following are the two main use of the throw keyword.

• Raise an exception manually: Sometimes we might need to raise a new exception like  ArgumentException()  to the user for bad user input, or if we have an unimplemented method and we don’t want anyone to use it, then we can write throw a new  InvalidOperationException()  from the try block.
• Re-throw an exception from catch block: Sometimes we might want to catch an exception, log the error, and then re-throw it back to the parent try/catch block to handle it.

try
{
 // statements that may cause exception
}
 catch
{
  throw ;
}

//Or

try
{
 // statements that may cause exception
}
catch (Exception exception)
{
  throw new Exception("Custom Exception Message", exception);
}

• We should throw exceptions only when an unexpected or invalid activity occurs in the program that prevents a method from being executed.
• Exception handling should not always be used for normal program flow instead of conditional handling, because it is difficult for programmers to maintain the code.

Example:

using System;
namespace ExceptionHandling
{
    class BankAccount
    {
        public string FirstName { get; private set; }
        public string LastName { get; private set; }
        public decimal Balance { get; private set; }

        public BankAccount(string firstName, string lastName, decimal amount)
        {

            if (string.IsNullOrEmpty(firstName))
            {
                throw new ArgumentException("FirstName cannot be empty");
            }
            if (string.IsNullOrEmpty(lastName))
            {
                throw new ArgumentException("LastName cannot be empty");
            }
            this.FirstName = firstName;
            this.LastName = lastName;
            this.Balance = amount;
        }

        public void Withdraw(decimal amount)
        {
            if (amount < 1)
            {
                throw new ArgumentException("Input amount can't be less than 1", nameof(amount));
            }

            if (amount > Balance)
            {
                throw new InvalidOperationException("Insufficient fund in account");
            }

            Balance = Balance - amount;
        }
    }

    public  class Program
    {   
        static void Main(string[] args)
        {
           // Creating object of "BankAccount" class and
           // and passing the values in the parameterized constructor

            BankAccount account = new BankAccount("Shekh", null, 100);
            Console.ReadKey();
        }
    } 
}

The ArgumentException is thrown when a method argument receives an invalid input value (example: null value). The InvalidOperationException indicates that a user attempted to use a method when the object was not in an appropriate state.

In the below program, we can throw the InvalidOperationException type in case we want to signal to our application that the withdrawal amount is higher than the available account balance.

static void Main(string[] args)
        {
            BankAccount account = new BankAccount("Shekh", "Ali", 100);

            // Trying to withdrawal amount higher than the available account balance.
            account.Withdraw(200);

            Console.ReadKey();
        }

Exception Filters

Exception filters are useful when you want to handle different types of exceptions using multiple catch blocks with different exception-type parameters.

Example: Exception Filters

using System;
namespace ExceptionHandlingExample
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("Please enter a number to divide 100: ");

            try
            {
                int number = int.Parse(Console.ReadLine());

                int result = 100 / number;

                Console.WriteLine($"100 / {number} = {result}");
            }
            catch (DivideByZeroException ex)
            {
                Console.Write($"Cannot divide by zero. Please try again.{ex.Message}");
            }
            catch (InvalidOperationException ex)
            {
                Console.Write($"Invalid operation. Please try again. {ex.Message}");
            }
            catch (FormatException ex)
            {
                Console.Write($"Not a valid format. Please try again.{ex.Message}");
            }
            catch (Exception ex)
            {
                Console.Write($"Error occurred! Please try again.{ex.Message}");
            }
            Console.ReadLine();
        }
    }
}

Properties Of C# Exception Class

The exception class is used to represent the errors that occur during the execution of an application.
The following are the useful properties of the  System.Exception  class helps to understand an exception easier.

Advantages of C# exception handling

The following are some of the advantages of exception handling in C#

• We can avoid the abnormal termination of the program.
• We can take any corrective measures that can solve the problems caused by the abnormal termination.
• Display easy-to-use error messages so that users can resolve the provided issues within their control.

Summary

In this article, we discussed Exception handling in C# using try, catch, and finally block.

Exception handling is a mechanism to handle errors that occur during the execution of a program.
It ensures that the flow of the program shouldn’t break when an exception occurs.
Exceptions in the program can occur because of multiple reasons such as the wrong input, coding errors made by the programmer, system errors, or other unpredicted things.
In C#, the exception handling is done by implementing the keywords try, catch, finally, and throw.

Hope you like this article and find it useful. If you have any questions, please post your comments below.

References: MSDN- Exception Handling in C#

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Shekh Ali

Meet Sheikh Ali, a skilled Software engineer and passionate a blogger. He enjoys sharing his expertise in C#, Java, SQL, Design Patterns, and other related topics through his writing. When he's not coding, Sheikh Ali can often indulge in his passions for reading books and fitness training.

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