DevExpress MVVM Framework. Scaffolding Wizard: new UI templates, features and tutorials in 14.2.

Building a CRUD application from scratch can easily become a time-consuming exercise in tedium. Thankfully, most data-bound applications implement a common set of UI and architectural patterns. With the DevExpress Scaffolding Wizard, with only a few clicks you can build a functional application with a well-organized and extendable MVVM structure. Tweak the view layouts and add some app specific functionality — and you’re done.

Since version 13.1, we’ve been improving the Scaffolding Wizard to add new features for coverage of the maximum number of out-of-the-box scenarios and support for many more capabilities to extend scaffolded applications.

The 14.2 release includes a great number of new Scaffolding Wizard features. Let’s overview some of what’s been added.

We previously presented two complex demos: the Outlook Inspired App with a MS Outlook GUI:

and the Touch-Enabled Hybrid App, designed for traditional desktop and touch-enabled devices alike.

These demos are based on code generated by the Scaffolding Wizard featuring several views (approximately twenty), custom logic and functionality. In the process of originally implementing these demos, we found the Scaffolding Wizard’s capabilities proved insufficient alone. This motivated us to significantly improve the Scaffolding Wizards in version 14.2.

The result is that most of the functionality of these demos can be simply generated by running a wizard. We’re eager to share some of our experience creating robust applications using code generated by the Scaffolding Wizard as a starting point.

New UI MDI View templates

Our first step was to develop two new templates for the Outlook Inspired and Hybrid UI apps, embodying our vision of the UI patterns which this class of applications should be built. You can follow along with these steps using the same templates and the Northwind Entity Framework model:

One great thing you’ll notice is that all our templates (Tabbed, Outlook Inspired and Hybrid) generate exactly the same Data Model and View Model code. This means you can easily move code and logic (excluding views) to separate assemblies. You could choose to publish two versions of your app: one for the traditional desktop and another for touch-enabled devices.

We rewrote the scaffolding code generators so most scenarios are supported out-of-the-box or with minimal effort.

Asynchronous data loading

How long a data request to the server will take to complete depends on several factors: the size of the database, the database server’s performance, available bandwidth, etc. If you’re using Entity Framework Code First, you may also have noticed the first DbContext initialization takes considerable time.

In version 14.2, scaffolded applications now make use of a separate thread to query and load data. The loaded records are then transferred to the main thread and displayed in a grid control or some other data-bound control displaying the collections of entities.

Support of the projections mechanism

The scaffolding is only aware of the data model, and knows nothing about how many records are stored in a table or the efficiency of loading these records from the server. That’s why the Scaffolding Wizard generates general code that will work in any scenario. This means that manual optimizations may be required. Scaffolded code provides extension points which you can use to customize the default data loading mechanism and solve for any performance issues.

Along with the simple scenario where a lot of heavy objects are requested over a narrow channel, we’ll need to be aware of a less glaring problem.

Entity Framework’s Navigation Properties are loaded on demand. If you have a grid column databound to a nested property on a navigation property (for instance, OrderItem.Order.Date), a separate request to the database to load the navigation property will be performed on each record. This may affect the responsiveness of the grid while scrolling the records.

All these issues can be resolved with a few lines of codes using projections. Despite the intricate name, projections are nothing more than the well-known LINQ Data transformations.

Here’s a tutorial demonstrating how to use projections to improve performance and address other concerns: How To Use Projections to Create Custom Queries and Optimize Performance

If you’re familiar with our grids for the desktop (XtraGrid, DXGrid for WPF), you may be wondering whether it’s possible to use our Instant Feedback mode to solve these performance problems in the most difficult cases (100,000+ heavy objects in the database)? The short answer is yes.

We’ll soon have direct support for Instant Feedback mode in Scaffolding and tell you how to easily switch your collection views to display a collection of objects using Instant Feedback without any UI changes (xaml).

IDataErrorInfo support out of the box

If your entity supports the IDataErrorInfo interface, validation errors will be shown in the UI and invalid entities won’t be saved to the database until the errors are resolved.

New commands

We added some new commands to simplify working with scaffolded application as an end-user:

• Save All – save changes in open detail edit forms
• Save and New – save changes to the current detail edit form, create a new record and open is edit form
• Save and Close - save changes in the current detail edit form and close it.
• Reset Changes - cancel all changes

New tutorials

Our Building Outlook-Inspired UI Application tutorial describes how to create a simplified version of our complex demos, with details descriptions of the main ideas and approaches of the original demos. Though this tutorial is quite long (11 steps), each step can be pursued separately to build an independent piece of functionality.

We have a new tutorial overviewing the projections mechanism: How To Use Projections to Create Custom Queries and Optimize Performance

To learn how to create an application bound to WCF see How to: Create an Application Bound to WCF Data Service.

We have also updated the existing tutorials, to illustrate the newly introduced features.

EF 5 is no longer supported

As of version 14.2, the Scaffolding Wizard no longer supports Entity Framework 5. If you have an existing Entity Framework 5 model, you will need to upgrade it to Entity Framework 6 before making use of the Scaffolding Wizard.

Note that MS Visual Studio 2012 uses Entity Framework 5 to generate database-first models (the ADO.NET Entity Data Model project item template). So if you use Visual Studio 2012, be sure to upgrade your entity model before using the Scaffolding Wizard.

We’re curious to hear your feedback on how you’re using scaffolding and what features or guides you’d like to see in the future.

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