Everything You Need to Know About Exception Handling in C#

When it comes to developing applications and software, exception handling is a tool you need in your toolbox. We’ve all been there — you think you’ve written a fantastic part of code but you suddenly run into unexpected problems. When that happens, it’s imperative that you know the fundamentals of exception handling, particularly when using C#.

In this article, I’m going to walk you through exception handling in C#. I’m going to cover topics such as what an exception is and when they occur, the various types of exceptions, and how to use try/catch/finally blocks to handle exceptions. Plus, I’ll share a few tips for making the whole process easier (which always makes it more fun!).

What is an Exception?

Let’s start with the basics. An exception is an event that disrupts the normal flow of a program. In other words, it’s an unexpected problem that a program encounters while it’s running and can cause it to crash or otherwise malfunction if it’s not handled properly. Exceptions in C# are objects that are derived from the System.Exception class.

Exceptions fall into two broad categories — checked and unchecked exceptions. Checked exceptions are those in which the compiler checks for the presence of a try/catch block where appropriate. Unchecked exceptions are generated at runtime and don't require programmers to handle them.

Types of Exceptions

Once you know what an exception is, it’s helpful to know the different types of exceptions that you may encounter. There are three major types of exceptions in C#

• System Exceptions: These are exceptions that are thrown due to errors in the application or environment. Examples include errors due to invalid input, attempting to open a file that doesn’t exist, or attempting to access an array element with an index that is out of bounds.
• Application Exceptions: These are exceptions that are thrown due to application logic errors such as trying to divide by zero or trying to access a null object.
• User-defined Exceptions: These are exceptions defined by the programmer. These are typically used to provide more customized error messages or to add additional error handling logic.

Using Try/Catch/Finally Blocks

Now that you know what an exception is, when it can occur and the types of exceptions that may occur, let’s look at how we can catch and handle them. That’s where try/catch/finally blocks come into play. Here's a brief overview of their structure:

• TRY - This denotes the beginning of a block of code that may throw an exception. If an exception is thrown, the code within the try block will not be executed.
• CATCH - This denotes the beginning of a block of code that will be used to handle the exception if one is thrown.
• FINALLY - This denotes the beginning of a block of code that will be executed regardless of whether an exception is thrown.

To better illustrate how these blocks are used, let’s take a look at a simple example. This example shows a function that will divide two numbers. If either number is zero, it will throw an exception.

public double Divide(int a, int b)
    {
        double result;
        try
        {
            result = a / b;
        }
        catch(DivideByZeroException ex)
        {
            Console.Error.WriteLine(ex);
            throw;
        }
        finally
        {
            // cleanup code
        }
        return result;
    }

Using the combination of the try, catch, and finally blocks, we can handle the exception if it occurs. In this case, if we encounter a divide by zero exception, we write information about it to the console, then re-throw the exception. In the finally block, we can put any code we need to execute regardless of whether an exception occurs, such as cleaning up resources.

More Tips for Handling Exceptions

Now that you know the basics of exception handling, here are a few more tips that can make your life easier.

• Always include a finally block: As illustrated in the example above, a finally block should always be used. This is because it's the only way to ensure that certain code gets executed regardless of whether an exception occurs.
• Know when to throw an exception: Not all exceptions need to be handled — sometimes it’s best to let the caller handle them. If a given method will never be able to recover from a particular error condition, it’s best to let the caller handle it.
• Use meaningful exception messages: When creating your own exceptions, try to include meaningful and descriptive error messages. This will make it easier for other developers to debug and understand what’s going on and why the exception was thrown.

Conclusion

Exception handling is an important skill to have when developing programs and applications. In this article, I’ve given you a brief overview of exception handling in C#. I’ve covered topics such as what an exception is, the different types of exceptions, how to use try/catch/finally blocks, and some tips for making the process easier. Hopefully this information will help you tackle any exception-related problems you encounter.