捕获另一个类抛出的异常？

Question

I thought I could catch an exception thrown by another class in my project, but I must be doing it wrong. In the first class, I'm surrounding my call to the other class with a try/catch block:

try
{    
    ImportPowerPoint.CreateTitle(textBoxPpt.Text, textBoxPkg.Text);
}
catch (FormatException ex)
{
    MessageBox.Show(ex.Message, "ERROR",
    MessageBoxButtons.OK,
    MessageBoxIcon.Warning);
}

In the second class, this is where I'm throwing the exception:

if (!_layoutMap[(int)Layouts.A].ContainsValue(Fields.Title))
    throw new FormatException("Standard (A) Layout does not contain a title.");

if (!_layoutMap[(int)Layouts.A].ContainsValue(Fields.Txt1))
    throw new FormatException("Standard (A) Layout does not contain a txt1.");

if (!_layoutMap[(int)Layouts.A].ContainsValue(Fields.Prompt))
  throw new FormatException("Standard (A) Layout does not contain a prompt.");

When I run the program, it breaks immediately where the exception is thrown, instead of displaying the error window that I defined in the try/catch block. Am I not handling this try/catch correctly?

For clarification, I'm forcing the exception to occur by removing certain pieces from the PowerPoint that I'm parsing. When the program fails, for instance, because I removed the Title Field, the exception thrown is of type FormatException. Shouldn't my catch in the calling class handle this?

EDIT: I think I may have found out something that is causing this to happen. The exception being thrown is in another thread. So, since it's in another thread, could this mean that this is why my try/catch isn't catching the exception?

Answer 1

It is breaking in the IDE to notify that the exception is thrown. If you press F5 again to continue running, your catch handler should be hit.

Answer 2

There is nothing class-related about exceptions. Your calling code ( ImportPowerPoint.CreateTitle(...); ) should be able to catch exceptions thrown by CreateTitle() .

See if your Visual Studio is configured to catch all exceptions (opposed to catching only unhandled ones):

1. Go to the 'Debug' menu
2. Select 'Exceptions...'
3. Uncheck check boxes under the 'Thrown' column

You would typically want the IDE to catch unhandled exceptions, so I would keep the other column checked.

Answer 3

The problem here appears to be because this is a multithreaded program. I'm looking at using the AppDomain.UnhandledException Event to handle my exceptions.