When you create a Microsoft BizTalk Server project in Microsoft Visual Studio, you can promote a field as both a distinguished field and a promoted property. As a best practice, you should promote a field as either a distinguished field or a promoted property. You should not promote a field as both a distinguished field and a promoted property.
This article describes some points to consider when you use distinguished fields and promoted properties.
When you use distinguished fields and promoted properties, consider the following points:
Use distinguished fields when you want to make decisions or to manipulate data in an orchestration. The pipeline disassembler will insert a Written property into the message context for items that are marked as a distinguished field.
Use promoted properties as criteria for message routing. However, notice that promoted properties are also available in an orchestration. The pipeline disassembler will insert a Promoted property into the message context for items that are marked as a promoted property.
Promoted properties are limited to 256 characters for performance reasons. For example, promoted properties are limited to 256 characters to improve performance in comparison operations and in storage operations.
Written properties do not have a size limit. However, large values that are written into the message context must still be processed by BizTalk Server. Therefore, performance may be affected.
A promoted property may not be available as a promoted property after you write a value into the message context. This situation can occur if the value that you write into the message context has the same name and namespace that was used to promote the property.
Properties that have a null value are not permitted in the message context. Therefore, if a null value is written into the message context, this value will be deleted.
For more information about messages in BizTalk Server 2006, visit the following Microsoft Developer Network (MSDN) Web site: