Identifying Exception Type in a handler Catch Block

Question

I have created custom exception class

public class Web2PDFException : Exception {     public Web2PDFException(string message, Exception innerException)         : base(message, innerException) { ... } } 

In my application how can I find out if it is my custom exception or not?

try {  ...  }  catch (Exception err) { //Find exception type here } 

Answer 1

When dealing with situations where I don't exactly know what type of exception might come out of a method, a little "trick" I like to do is to recover the Exception's class name and add it to the error log so there is more information.

try {    <code>  } catch ( Exception caughtEx ) {    throw new Exception("Unknown Exception Thrown: "                        + "\n  Type:    " + caughtEx.GetType().Name                        + "\n  Message: " + caughtEx.Message); } 

I do vouch for always handling Exceptions types individually, but the extra bit of info can be helpful, specially when dealing with code from people who love to capture catch-all generic types.

Answer 2

UPDATED: assuming C# 6, the chances are that your case can be expressed as an exception filter. This is the ideal approach from a performance perspective assuming your requirement can be expressed in terms of it, e.g.:

try { } catch ( Web2PDFException ex ) when ( ex.Code == 52 ) { } 

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Assuming C# < 6, the most efficient is to catch a specific Exception type and do handling based on that. Any catch-all handling can be done separately

try { } catch ( Web2PDFException ex ) { } 

or

try { } catch ( Web2PDFException ex ) { } catch ( Exception ex ) { } 

or (if you need to write a general handler - which is generally a bad idea, but if you're sure it's best for you, you're sure):

 if( err is Web2PDFException)  {  } 

or (in certain cases if you need to do some more complex type hierarchy stuff that cant be expressed with is)

 if( err.GetType().IsAssignableFrom(typeof(Web2PDFException)))  {  } 

or switch to VB.NET or F# and use is or Type.IsAssignableFrom in Exception Filters