Coding Bolt

In C#, there’s a keyword we rarely use: goto. In programming, using goto is considered bad practice because it breaks the logical flow, making code harder to read and maintain. But what if I told you that throwing exceptions sometimes is like using a goto? Let’s explore this analogy and understand why YOU are using goto in your code and you are lying to yourself about it.

What’s Wrong with goto?

To understand the comparison, let’s first recap why goto has such a bad reputation. Using goto enables you to jump directly to a labeled section of code, often breaking the structured flow of your program and making it tough to follow.

For example:

public void ProcessData()
{
    if (someCondition)
        goto Error;

    PerformSomeAction();
    return;

Error:
    LogError();
}

While goto is technically valid, it’s usually discouraged because it disrupts the natural top-to-bottom reading of code. The result? Code that’s harder to understand and maintain.

Throwing Exceptions: A goto in Disguise?

When you throw an exception, the flow of your program changes drastically, often “jumping” back to the nearest appropriate catch block or even to higher-level handlers if none are found. This abrupt change in control flow is similar to a goto because it immediately skips over any remaining code and directs the program to handle the exception elsewhere.

Consider this example:

public void ProcessData()
{
    try
    {
        if (someCondition)
            throw new InvalidOperationException("An error occurred.");

        PerformSomeAction();
    }
    catch (InvalidOperationException ex)
    {
        LogError(ex);
    }
}

Here, when throw is executed, control flow jumps out of ProcessData, skipping over PerformSomeAction() entirely and sending control to the nearest catch block. It’s as though we’ve placed an invisible goto statement that skips any remaining logic and jumps straight to error handling.

Throwing exceptions can sometimes make code less predictable and harder to follow. Here’s why:

1. Unpredictable Flow: When exceptions are thrown without clear intent or structure, it can make code harder to follow, as the flow might abruptly jump back multiple call levels without a clear path.
2. Harder to Maintain: When exceptions are used excessively for control flow, it can make maintenance difficult because you must trace back to each throw statement to understand how control will flow.
3. Performance Costs: Throwing exceptions is also costly in terms of performance. If used as a way to “jump” out of a block of code, it’s an inefficient and costly control mechanism.

When Exceptions Are the Right Choice (and When They’re Not)

It’s essential to distinguish between using exceptions for genuine errors and using them as a tool for managing flow. Here’s when exceptions are appropriate and when they’re not:

• Appropriate: Use exceptions when handling unexpected, exceptional conditions. For instance, a database connection failing.
• Inappropriate: Don’t use exceptions as a way to return control flow in normal, expected conditions. If a condition is expected, consider using conditional statements instead.

Conclusion

Throwing exceptions can, at times, feel like a goto, altering the control flow in ways that can make code harder to follow. While exceptions are crucial for handling unexpected errors, they shouldn’t be used as control mechanisms in regular, expected logic paths. Please choose the right patterns for handling both expected and unexpected conditions, so we can make our C# code more readable, maintainable, and performant.

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