Question

I have a simple try/catch block

try
{
     // Open the connection
     _connection.Open(); // [1]
}
catch( OracleException ex ) // [2]
{
     // Handle the exception
     int x = ex.ErrorCode;
}

The catch is never executed and the runtime reports ‘OracleException was unhandled’ at [1] which just makes my head spin. Clearly, I have a catch statement for the associated exception type. I’ve even tried the fully qualified type, Oracle.DataAccess.Client.OracleException at [2] and still the exception is unhandled.

The only way I can actually get the catch to work is by catching System.Exception at [2]. What is causing this odd behavior?

Answer 1

Are you dynamically loading assemblies at all, possibly using Assembly.LoadFrom or something similar? If so, you might be hitting a situation where the type that you have mutiple types loaded into different load contexts.

Assemblies loaded into different context present the same types with different identities so they do not match type equality checks etc.

From MSDN

• The load context contains assemblies
  found by probing: in the GAC, in a
  host assembly store if the runtime is
  hosted, or in the ApplicationBase and
  PrivateBinPath of the application
  domain. Most overloads of the Load
  method load assemblies into this
  context.

• The load-from context contains
  assemblies for which the user
  provided a path not included in the
  directories searched by probing.
  LoadFrom, CreateInstanceFrom, and
  ExecuteAssembly are examples of
  methods that load by path.

Of course this is just a guess, so I might be wrong.