>>>I have this code in a prg.
>>>
>>>Define Class CodesMainTxtChar As textbox_char Of dataform
>>>...
>>>
>>>EndDefine
>>>
>>>While compiling the project I receive this error:
>>>
>>>Program codesmain.prg has the following errors:
>>> Program DATAFORM - Undefined
>>>
>>>I tried EXTERNAL CLASS dataform but I did not help.
>>>How can I prevent this error?
>>>
>>>Thanks in advance
>>>Anthony
>>
>>You have a classlib called dataform, which hold the textbox_char class?
>
>Yes.

The DataForm classlibrary needs to be in the project. Included or excluded should not matter. If this doesn't get you past the problem, try to compile classlib DataForm.