BizTalk 2010 Recipes : Creating Property Schemas

1. Problem

You want to subscribe to a message based on the contents of the message.

2. Solution

Property schemas allow you to promote properties so that they can be used when setting up filter expressions. As long as the PassThruReceive pipeline is not used, these promoted properties are added to the message context during pipeline processing. Once added to the message context, they can be used as filter expressions on send ports. These properties are also available to be evaluated or modified in orchestrations. To create a property schema and promote a property, follow these steps:

3. How It Works

Once you have deployed the solution with the promoted properties, they may be used to perform content-based routing on the documents. Following is a simple example of content-based routing. Assume you have the following two documents:

<Person>
        <Name>
                <FirstName>John</FirstName>
                <LastName>Doe</LastName>
        </Name>
        <Birthdate>1979-05-31</BirthDate>
        <StateOfBirth>Washington</StateOfBirth>
</Person>

<Person>
        <Name>
                <FirstName>Sam</FirstName>
                <LastName>Evans</LastName>
        </Name>
        <Birthdate>1973-03-15</BirthDate>
        <StateOfBirth>California</StateOfBirth>
</Person>

You would like to send each of these documents to a different destination based on the StateOfBirth field. After creating a simple schema to represent these documents, the StateOfBirth element is promoted using the steps outlined in the "Solution" section. Once the project is built and deployed, you are able to reference the promoted property when creating a send port filter expression. In this example, two distinct send ports are created. Figure 3 shows the filter expression on the first send port. The subscription is based on the value of the StateOfBirth field being equal to Washington.

Figure 3. Subscription for Washington

On the second send port, the subscription is based on the value of the StateOfBirth field being equal to California, as shown in Figure 4.

Figure 4. Subscription for California

Although this example is simple, it is easy to see how you can leverage this feature to create content-based routing scenarios through the use of promoted properties.

It is also possible to create message context properties that do not exist in the message itself, but only in the message context. This may be valuable when you are not allowed to modify the schema but would like to associate additional information with the document. This may be accomplished by adding a node to a property schema and setting its Property Schema Base property to MessageContextPropertyBase. This property is then available and can be set in an orchestration, and ultimately, the document may be routed based on its value. For example, perhaps you would like to calculate the age for each person processed in the preceding example, but you cannot add an Age element to the schema. As opposed to adding a node to the schema, a node is added to the property schema, as shown in Figure 5.

Figure 5. Adding a property to message context

After building and redeploying the solution, a second property, Age, is now available (see Figure 6) for generating filter expressions.

Figure 6. The new value is available in the filter expressions

To complete the scenario, you would do the following:

• Create an orchestration that subscribes to all of the documents with no value for Age.

• In this orchestration, calculate the Age value based on the birth date, and set the property accordingly.

• Send the document back into the MessageBox database.

• Add a second filter expression to the existing send ports to subscribe based on the StateOfBirth and if the Age value is present.

In summary, content-based routing is a typical scenario, and property schemas are used to extend the message context properties that come with BizTalk Server.