MSDN Magazine - July 2008 - (Page 61)

Cities 1 Now that the initial setup is complete, let’s move ahead and add the cities-served functionality. Adding a City As mentioned earlier, Contoso Classifieds places each city’s listings in its own from e in entities where e["CategoryID"] == "For Sale" select e authority, which enables you to choose the datacenter it is hosted in. (While that Figure 5 Entity Data Model Used by the App Notice I say flex property. As previously feature is not currently supported in the beta of SSDS, it will be mentioned, entities in a container must have unique IDs that will supported by the time the product is released.) limit you from using the distinguished system property ID. Also The code for adding the city is similar to the code used for the notice the query syntax I have issued. SSDS uses a LINQ-like queinitial setup. Using the SOAP proxy, set the credentials, create an ry syntax, which should look familiar to most developers who use empty scope, set the authority ID, and issue the create: the .NET Framework. SSDSClient.Authority cityAuth = If you look back at the administrative application shown in Fignew SSDSClient.Authority(); ure 4, you will notice a tree view that represents the listing catecityAuth.Id = cityAuthorityName; gories and two textboxes for adding category headers and listing ssdsProxy.Create(serviceScope, cityAuth); categories. Let’s dive into the implementation behind adding a Now that the new city authority is created, add a pointer entity to category header. the Cities container in the main contosoclassifieds authority: As with the previous code, you use the SitkaSOAPServiceClient, serviceScope.AuthorityId = "contosoclassifieds"; set the credentials, and set the scope to the contosoclassifieds auserviceScope.ContainerId = "Cities"; thority and the Categories container. Now all you need to do is //Create the City Entity, and set its properties appropriately create the entity: SSDSClient.Entity cityEntity = new SSDSClient.Entity(); cityEntity.Id = cityAuthorityName; cityEntity.Kind = "CityServed"; cityEntity.Properties = new Dictionary (); cityEntity.Properties["AuthorityUri"] = string.Format("{0}.data.data.beta.mssds.com/v1/", cityAuthorityName); cityEntity.Properties["Name"] = txtCity.Text; //Issue the create to SSDS ssdsProxy.Create(serviceScope, cityEntity); SSDSClient.Scope serviceScope = new SSDSClient.Scope(); serviceScope.AuthorityId = "contosoclassifieds"; serviceScope.ContainerId = "Categories"; SSDSClient.Entity categoryHeaderEntity = new SSDSClient.Entity(); categoryHeaderEntity.Id = CategoryID; categoryHeaderEntity.Kind = "Category"; tities can have the same Kind, that does not force the entities to be homogeneous. The entity can have whatever shape you would like. A better approach to this scenario might be to have two different entity Kinds, Category and Listing Category, and to have a flex property of CategoryID in all entities. That would allow you to issue a query such as: Let’s recap for a moment. I’ve created a main contosoclassifieds authority that holds all of the systemwide data. In that authority, there is a Cities container that has an entity for each city the application will serve. That entity contains the display name of the city, along with a pointer to the authority that contains all the listings. You can also add a single flex property that will contain the category name. Notice that this only adds a single property to the flex properties collection: categoryHeaderEntity.Properties = new Dictionary (); categoryHeaderEntity.Properties["CategoryName"] = CategoryName; Adding Categories Figure 6 Adding Flex Properties //Determine whether this is the first listing //category being added to this header if (categoryEntity.Properties.Count > 2) { propCount = ((categoryEntity.Properties.Count - 1) / 2); propCount++; } else { propCount = 1; } //Create the FlexProperties for the new listing category string listingIdPropName = string.Format ("ListingCategoryID{0}", propCount); string listingNamePropName = string.Format ("ListingCategoryName{0}", propCount); categoryEntity.Properties[listingIdPropName] = ListingCategoryID; categoryEntity.Properties[listingNamePropName] = ListingCategoryName; //Issue the update to SSDS ssdsProxy.Update(serviceScope, categoryEntity); Up to this point, you’ve just added authorities, containers, and entities. The next step is to implement the listing categories feature. To do so involves using the query, update, and delete functionality of SSDS. Contoso Classifieds will support a category header, with sub categories below it to hold the actual postings from users. If you were to use a relational model for this data, you would typically use a header/line pattern for the data. The flexible entity data model used by SSDS, however, allows your data to take whatever shape you like. In the case of the Contoso Classifieds application, I chose to use a single entity to represent each category header and all the subcategories that belong to it (see Figure 5). Please note that I am using this pattern to simply show the flexible nature of an entity and to illustrate that, although multiple enmsdnmagazine.com July 2008 61 http://msdnmagazine.com

Table of Contents Feed for the Digital Edition of MSDN Magazine - July 2008

MSDN Magazine - July 2008 Contents Toolbox CLR Inside Out Flex Your Data Data Points Advanced Basics Office Space Cutting Edge Data Services ADO.NET Data and WPF Transactions WCF P2P Test Run Security Briefs Foundations .NET Matters {End Bracket}

MSDN Magazine - July 2008

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