There are two ways to get content of message specified filed directly in BizTalk in message.
Distinguished fields and Promoted property.
When you need to access the content of filed only in orchestration level prefer Distinguished fields. Distinguished fields are xpath equivalent and these xpath stored insisted XSD. Due these fields are xpath equivalent these are light weight. There are no restriction of size of filed. There is common practice to use Distinguished properties instead of xpath, if any change in namespace of any schema, all xpath on the schema used in orchestration are lost. If you used distinguished properties then on update of target namespace all , distinguished proprieties also update and there will no change in orchestration.
When to use distinguished fields:
If you make decision, read values, update values of any message inside the orchestration Use distinguished properties.
When required value of filed at port level then used Promoted properties. These Usually used for Routing purposes. When we promoted any field in Schema, these fields stored in separated Schema, known as Property schema. These have performance over head, due to these promoted values stored in Message box. There is also restriction on Size of promoted properties the field size should not be exceed more the 256 character.
When to use Promoted Properties:
– Driving built in pipeline component behavior