Assume that you have a Class Library where all the commonly used functions are written and compiled.
If that class library uses any keys from an app.config file, how will you add those keys in BizTalk Server Run time?
Answer is very simple.
BizTalk Server too has a config file which will be access during run time.
So, if you use any external library in any orchestration and if that External Library needs any key values from Config file, all those key value pairs should be copied to the BizTalk Server Config file for the Orchestration to run properly.
BizTalk Server config file can be found the below location.
C:\Program Files (x86)\Microsoft BizTalk Server 2009\
C:\Program Files (x86)\Microsoft BizTalk Server 2009\BTSNTSvc64.exe.config
So, next time if your external library is using any config file, make sure that all those keys are also there in BizTalk Server Config file.
Note: Once the config file is updated, host instance should be restarted to reflect the values.