View source for Exception Handling Best Practices

= Exception Handling Best Practices MSDN =
MSDN: [https://learn.microsoft.com/en-us/dotnet/standard/exceptions/best-practices-for-exceptions Best practices for exceptions]
__TOC__

Exception handling is a critical aspect of software development, ensuring that applications can gracefully handle errors and prevent crashes. In this article, we'll delve into best practices for handling and creating exceptions to enhance the robustness and reliability of your applications.

== Rethrowing Exceptions ==

When an exception is caught and rethrown in C#, it's essential to ensure that the original stack trace is preserved. This is crucial for effective debugging and understanding the flow of execution leading up to the exception. 

=== Use just throw for rethrowing ===

The correct way to rethrow an exception without losing the original stack trace is to use the `throw;` statement without specifying a variable. This simply rethrows the caught exception as-is, maintaining its original stack trace intact.

<pre>
try {
    // Some code that may throw an exception
}
catch (Exception ex) {
    // Handle the exception
    // Rethrow without losing original stack trace
    throw;
}
</pre>

=== Avoiding throw varException ===

Using `throw <var>;` to rethrow an exception can inadvertently create a new exception object with its own stack trace, effectively '''obliterating''' the original one. This makes debugging much more challenging as the original source of the exception may become obscured.

<pre>
try {
    // Some code that may throw an exception
}
catch (Exception ex) {
    // Handle the exception
    // Incorrect way - creates a new exception object and stack trace
    throw ex;
}
</pre>

'''Always use `throw;`''' when rethrowing exceptions to ensure that the original stack trace is preserved, if not intended otherwise. This practice greatly aids in diagnosing and troubleshooting issues within your codebase.

[https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/ca2200 CA2200: Rethrow to preserve stack details]

== Best Practices according to MSDN ==

=== Use of try/catch/finally Blocks ===

Utilize try/catch/finally blocks to encapsulate code that may potentially generate exceptions. This construct allows for error recovery and resource cleanup. Ensure that catch blocks are ordered from the most derived to the least derived exceptions to handle specific error conditions effectively.

=== Handling Common Conditions ===

Anticipate and handle common conditions that may trigger exceptions without necessarily throwing them. By incorporating conditional checks, such as verifying connection states before operations like closing connections, you can mitigate exceptions and enhance the resilience of your code.

=== Designing Classes for Exception Avoidance ===

Design classes with methods or properties that enable the avoidance of actions that could lead to exceptions. Providing functionalities to check conditions before performing operations helps preemptively prevent exceptions, enhancing the stability of your application.

=== Throwing Exceptions Strategically ===

Throw exceptions instead of returning error codes to ensure that failures are appropriately handled and not overlooked. Utilize predefined .NET exception types whenever possible and adhere to naming conventions for custom exception classes.

=== Additional Best Practices ===

* Include localized error messages for every exception to enhance user understanding.
* Provide additional properties in custom exceptions only when programmatically useful.
* Ensure that stack traces are helpful for debugging by strategically placing throw statements.
* Implement mechanisms to restore application state in case of incomplete operations due to exceptions.
* Capture exceptions using `System.Runtime.ExceptionServices.ExceptionDispatchInfo` for preserving call stacks and rethrowing later.


More to read:
* Nunit: [https://docs.nunit.org/articles/nunit/writing-tests/assertions/classic-assertions/Assert.Throws.html Assert.Throws]
* LinkedIn: [https://www.linkedin.com/advice/3/what-best-practices-handling-exceptions-test-automation-pic9c What are the best practices for handling exceptions in test automation strategies?]