How to determine if an exception is of a particular type

before your current catch add the following:

catch(DbUpdateException ex)
{
  if(ex.InnerException is UpdateException)
  {
    // do what you want with ex.InnerException...
  }
}

From C# 6, you can do the following:

catch(DbUpdateException ex) when (ex.InnerException is UpdateException)
{
    // do what you want with ex.InnerException...
}