standards-c-sharp

How to rethrow an exception from a catch block

• When rethrowing an exception simply throw; it. Do not throw ex; as this loses the original call stack information, making it look like the exception originated inside your catch block.
• The exception to this rule is if you have wrapped your exception to be more specific.

Don’t

try
{
    return myService.GetData();
}
catch (MyServiceException ex)
{
    // do something useful here, and then:
    throw ex; // the `ex` makes it look like the exception originated from _this_ line we have lost the original context
}

Do

try
{
    return myService.GetData();
}
catch (MyServiceException)
{
    // do something useful here, and then:
    throw; // note no `ex`: now at least the exception originates from the original line 
}

Do

try
{
    return myService.GetData();
}
catch (MyServiceException ex)
{
    // Wrap the exception to give the consumer more information. Remember to set the InnerException property.
    var betterEx = new MyApplicationException("Something bad happened with myService")
    {
         InnerException = ex, // we preserve the context of our original exception here
         UserInfo = userInfo
    }
    throw betterEx;
}

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