**Course Title:** Mastering C#: From Fundamentals to Advanced Programming **Section Title:** Error Handling and Exception Management **Topic:** Write a C# program that includes custom exception handling and logging errors.(Lab topic) **Objective:** In this lab topic, you will learn how to create a C# program that includes custom exception handling and logging errors. You will understand how to define and use custom exceptions, handle exceptions using try-catch blocks, and log errors to a file. **Custom Exceptions:** Custom exceptions are used to handle specific error scenarios that are not covered by the built-in exceptions in C#. To create a custom exception, you need to derive a class from the `Exception` class. ```csharp using System; public class InsufficientBalanceException : Exception { public InsufficientBalanceException(string message) : base(message) { } } ``` In the above code, we have created a custom exception called `InsufficientBalanceException`. This exception can be used to handle scenarios where the account balance is insufficient. **Try-Catch Blocks:** Try-catch blocks are used to handle exceptions in C#. The `try` block contains the code that might throw an exception, and the `catch` block contains the code that will be executed if an exception is thrown. ```csharp using System; public class Program { public static void Main(string[] args) { try { WithdrawMoney(1000); } catch (InsufficientBalanceException ex) { Console.WriteLine("Error: " + ex.Message); } } public static void WithdrawMoney(int amount) { int balance = 500; if (balance < amount) { throw new InsufficientBalanceException("Insufficient balance in account"); } else { balance -= amount; Console.WriteLine("Withdrawal successful. Remaining balance: " + balance); } } } ``` In the above code, we have used a try-catch block to handle the `InsufficientBalanceException`. If the balance is insufficient, the `WithdrawMoney` method throws an `InsufficientBalanceException`, which is caught by the catch block and handled accordingly. **Logging Errors:** Logging errors is an important aspect of error handling. It allows you to track errors and diagnose issues. In C#, you can use the `System.IO` namespace to log errors to a file. ```csharp using System; using System.IO; public class ErrorLogger { public static void LogError(string error) { string logFile = @"C:\ErrorLogs\error.log"; File.AppendAllText(logFile, DateTime.Now.ToString() + ": " + error + Environment.NewLine); } } public class Program { public static void Main(string[] args) { try { WithdrawMoney(1000); } catch (InsufficientBalanceException ex) { ErrorLogger.LogError(ex.Message); Console.WriteLine("Error: " + ex.Message); } } public static void WithdrawMoney(int amount) { int balance = 500; if (balance < amount) { throw new InsufficientBalanceException("Insufficient balance in account"); } else { balance -= amount; Console.WriteLine("Withdrawal successful. Remaining balance: " + balance); } } } ``` In the above code, we have added an `ErrorLogger` class that logs errors to a file. The `LogError` method appends the error message to a log file. **Best Practices:** Here are some best practices to keep in mind when implementing custom exception handling and logging errors in C#: * Use meaningful error messages that describe the error. * Use try-catch blocks to handle exceptions and prevent crashes. * Log errors to a file to track issues. * Use a standardized error handling approach throughout the application. **Conclusion:** In this lab topic, you learned how to create a C# program that includes custom exception handling and logging errors. You understood how to define and use custom exceptions, handle exceptions using try-catch blocks, and log errors to a file. You also learned some best practices to keep in mind when implementing custom exception handling and logging errors in C#. **Additional Resources:** * [Microsoft Docs: Exception Handling in C#](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/exceptions/) * [Microsoft Docs: File.AppendAllText Method](https://docs.microsoft.com/en-us/dotnet/api/system.io.file.appendalltext?view=netcore-3.1) **What's Next:** In the next topic, you will learn about collections in C#, including List, Dictionary, Queue, and Stack. You will understand how to create and use collections to store and manage data. **Leave a comment or ask for help:** If you have any questions or need further clarification on any of the topics covered in this lab topic, please leave a comment below. We'll be happy to help.