`throw` vs. `throw new Exception()`: When Should You Rethrow Exceptions in C#?

C# exception handling: The difference between throw and throw new Exception()

When handling C# exceptions, programmers may encounter two similar-looking structures:

try { ... }
catch { throw }

and

try { ... }
catch (Exception e) { throw new Exception(e.Message); }

While both throw exceptions, there are key differences in their behavior.

throw

A throw statement without parameters rethrows the original exception that caused the try block to fail. This means that the stack trace of the original exception is preserved, making it easier to debug and trace the source of the error.

throw new Exception()

On the other hand, throw new Exception(e.Message) creates a new exception instance with its Message attribute set to the message of the original exception. However, this has several disadvantages:

• Stack trace lost: The stack trace for the new exception is reset, destroying any tracing information from the original exception source.
• Type information lost: The new exception has lost the type of the original exception, making it difficult to determine its exact nature.
• Additional information lost: Some exceptions, such as ArgumentException, contain additional information (such as ParamName) that is lost when creating new exceptions of different types.

Best Practices:

In most cases, it is strongly recommended to avoid using throw e or throw new Exception(e.Message) to rethrow exceptions. Consider the following:

• Preserve original stack trace: To rethrow the original exception and preserve its stack trace, use throw;.
• Wrapped exceptions: In some cases it may be necessary to wrap all exceptions in a custom exception object to provide additional information. However, always ensure that your custom exception has all four exception constructors and preserves the properties of the original exception, including the stack trace, by passing them as InnerException arguments.

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