Best practices for catching and re-throwing .NET exceptions

Terrapin_357 0
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What are the best practices to consider when catching exceptions and re-throwing them? I want to make sure that the Exception object's InnerException and stack trace are preserved. Is there a difference between the following code blocks in the way they handle this?

try
{
    //some code
}
catch (Exception ex)
{
    throw ex;
}

Vs:

try
{
    //some code
}
catch
{
    throw;
}
rethrow exception-handling .net c#
11 Answers

The way to preserve the stack trace is through the use of the throw; This is valid as well

try {
  // something that bombs here
} catch (Exception ex)
{
    throw;
}

throw ex; is basically like throwing an exception from that point, so the stack trace would only go to where you are issuing the throw ex; statement.

Mike is also correct, assuming the exception allows you to pass an exception (which is recommended).

Karl Seguin has a great write up on exception handling in his foundations of programming e-book as well, which is a great read.

Edit: Working link to Foundations of Programming pdf. Just search the text for "exception".

user_770

If you throw a new exception with the initial exception you will preserve the initial stack trace too..

try{
} 
catch(Exception ex){
     throw new MoreDescriptiveException("here is what was happening", ex);
}
Mike_15730

When you throw ex, you're essentially throwing a new exception, and will miss out on the original stack trace information. throw is the preferred method.

Forgotten_Semicolon_19600

The rule of thumb is to avoid Catching and Throwing the basic Exception object. This forces you to be a little smarter about exceptions; in other words you should have an explicit catch for a SqlException so that your handling code doesn't do something wrong with a NullReferenceException.

In the real world though, catching and logging the base exception is also a good practice, but don't forget to walk the whole thing to get any InnerExceptions it might have.

swilliams_7360

I would definitely use:

try
{
    //some code
}
catch
{
    //you should totally do something here, but feel free to rethrow
    //if you need to send the exception up the stack.
    throw;
}

That will preserve your stack.

1kevgriff_12260

You may also use:

try
{
// Dangerous code
}
finally
{
// clean up, or do nothing
}

And any exceptions thrown will bubble up to the next level that handles them.

Erick_13730
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