How to check for the existence/count of a given distinguished property in BizTalk

 System.Convert.ToInt32(xpath(Response_Select_Query,”count(copy xpath from schema and paste here)”));

———————————————-OR———————————————————————————

theStringValue = xpath(inputMessage, “string(//*[local-name()=’MyElementName’])”);

from the following link

http://www.arquitecturadesoftware.org/blogs/joaomartins/archive/2007/04/11/biztalk-check-if-promoted-property-exists-in-context.aspx

And now you can use System.String.IsNullOrEmpty(theStringValue) to check if the value is present.