The begin sequence - recover - end sequence statements are widely used in VO applications, and the X# compiler translates it mainly in the try - catch and end try statements. So, if you are transporting VO code, you can keep these statements safely, but for new code please use the .NET equivalents Try - Catch. Where the X# compiler adds functionality in the translation is in the recover statement, to support the VO break command, and encapsulates the exception in an usual. And it adds support for the CanBreak() function.

The biggest difference between the error handling in .NET and Visual Objects stays in the ErrorBlock() handling. Please see the relative topic: The VO ErrorBlock

Unfortunately, in the begin sequence - end sequence construct seems to be a major compatibility issue. This code for example:

local uVal1 as usual
local uVal2 as usual
local uVal3 as usual

begin sequence  
  uVal1 := "Hi"
  uVal2 := 2
  uVal3 := uVal1 + uVal2
end sequence

when executed in VO shows a runtime error, as expected. When you execute it in X#, it does not shows any runtime error. This could lead to not see runtime errors in your migrated VO application. Until the X# development team is able to add some enhancements in their own runtime, you should better use the .NET try - catch statements, and if you need to remain source compatible between VO and X#, you can use code like this:

#ifdef __XSHARP__
  try
#else
  begin sequence
#endif  
uVal1 := "Hi"
uVal2 := 2
uVal3 := uVal1 + uVal2
#ifdef __XSHARP__
  catch oEx as Exception
  ErrorBox{ nil, oEx:Message }:Show()
  end try
#else
  end sequence
#endif