BizTalk 2009 : Creating More Complex Pipeline Components (part 2) - Schema Selection in VS .NET Designer

2. Schema Selection in VS .NET Designer

The property MyDocSpec in the previous section's MyProber class is actually of type SchemaWithNone. SchemaWithNone is a class that lives in the Microsoft.BizTalk.Component. Utilities.dll assembly. Defining a property of type SchemaWithNone will give the user a drop-down list of all deployed schemas within the current BizTalk Management Database. The class has one public constructor, SchemaWithNone, which initializes a new instance of the SchemaWithNone class. Tables 1 and 2 list the public properties and methods of the class.

As you can see in Figure 1, the properties for the SchemaWithNone class are available in the IDE. If you notice the InboundDocSpec property, it is a list of all the schemas that are currently deployed to the BizTalk solution. The SchemaWithNone property allows you to select one and only one schema from the deployed schemas, and this information will be used to populate the properties of the object as defined previously (AssemblyName, DocSpecName, and so on).

In the example from the preceding section, you want your developer to select only one schema, but what if your developer needs multiple schemas, for example, to handle different message formats in one component? In many cases, your component will be able to handle a variety of schemas; in this case, you need to use the SchemaList property.

In the case where your property needs to select multiple schemas, you need to use the SchemaList object. Such an object will provide developers with an associate window from which they can choose multiple schemas. The selected schemas will be available as a collection of schemas within a main class. The IDE will present the screen shown in Figure 2.

Figure 1. SchemaWithNone example in VS .NET

Figure 2. SchemaList example in VS .NET

2.1. Decorating Your Properties

It is important to consider the usability of your components from within the Visual Studio IDE. If you simply expose a public property from within your pipeline component, two things will happen. First, the property name that is displayed in the IDE will be the name of the property . Second, there is no public description for what the property actually does. In order to make your components usable, you can use custom attributes to decorate your properties with metadata so that the developer experience is improved. The two main attributes you can use to do this are described next.

2.1.1. Using the DisplayName and Description Attributes

The DisplayName attribute allows you to set the name for the property that will be displayed in the IDE. The Description attribute sets the description box within the VS .NET designer to a friendly description. Figure 3 shows the effect of these attributes. The following code snippet demonstrates how these attributes are to be used:

'<summary>
   'this property will contain a single schema
'</summary>
<Description("The inbound request document specification. Only messages of this _
type will be accepted by the component.")> _
<DisplayName("Inbound Specification")> _
 Public Property InboundFileDocumentSpecification() As _
Microsoft.BizTalk.Component.Utilities.SchemaWithNone
    Get
       Return _InboundFileDocumentSpecification
    End Get
    Set(ByVal Value As Microsoft.BizTalk.Component.Utilities.SchemaWithNone)
    _ InboundFileDocumentSpecification = Value
    End Set
End Property

					  

Figure 3. DisplayName and Description attributes set