Why is this an issue?

In C#, the throw statement can be used in two different ways:

By specifying an expression

In the software development context, an expression is a value or anything that executes and ends up being a value. The expression shall be implicitly convertible to System.Exception, and the result of evaluating the expression is converted to System.Exception before being thrown.

try
{
}
catch(Exception exception)
{
  // code that uses the exception
  throw exception; // The exception stack trace is cleared up to this point.
}

In this case, the stack trace, will be cleared, losing the list of method calls between the original method that threw the exception and the current method.

Without specifying an expression

This syntax is supported only in a catch block, in which case, that statement re-throws the exception currently being handled by that catch block, preserving the stack trace.

try
{
}
catch(Exception exception)
{
  // code that uses the exception
  throw; // The stack trace of the initial exception is preserved.
}

Exceptions

It is allowed using the thrown exception as an argument and wrapping it in another exception.

try
{
}
catch(Exception exception)
{
  throw new Exception("Additional information", exception);
}

How to fix it

The recommended way to re-throw an exception is to use the throw statement without including an expression. This ensures that all call stack information is preserved when the exception is propagated to the caller, making debugging easier.

Code examples

Noncompliant code example

try
{
}
catch(Exception exception)
{
  throw exception;
}

Compliant solution

try
{
}
catch(Exception)
{
  throw;
}

Resources

Documentation