For the past year, I have led an initiative at my company to use Silverlight 4 and WCF RIA Services on the majority of our user interface projects. While these projects have been largely successful, we began running into serious performance problems when trying to squeeze large amounts of data onto our views. The problem wasn’t fetching the data, but rather scrolling and viewing the data in our DataGrids.

One of the largest optimizations we made was to set the windowless parameter back to false. But the root cause pointed to an overload of the Silverlight visual tree. Simply put, there’s only so much you can show on the screen at once, even with virtualization turned on. With a giant excel-like editable datagrid that sprawls the screen, there’s no getting around visual tree overload (especially when scrolling). We evaluated every commercial SL datagrid on the market, and chose the default SDK DataGrid from MS because it fared really well in our scenario.

In the end, we performed many optimizations to get the product to “acceptable” performance, but this motivated me to begin researching WPF as an alternative. I did a massive comparison of all the different WPF/Silverlight datagrids, and one theme remained the same: WPF has much more visual rendering power than Silverlight. These findings have made me dead-set on trying my best to see if WPF can be the platform-of-choice for major apps going forward, but it turns out that the performance honeymoon was short lived.

As I began to build a prototype in WPF, the giant glaring gaps quickly began to emerge. The first was that WPF doesn’t support RIA Services. This is a huge negative, and unless I find a hack to somehow get a client support for WPF, it will force us back to silverlight. The second big one was the validation story. Notice those “free” beautifully animated popout error messages in the datagrid and dataform controls in Silverlight? These are nowhere to be found in WPF. I have yet to find anyone who has replicated them in WPF, and I haven’t had time to try myself. Also, WPF does not have INotifyDataErrorInfo, so any async validation is going to be far less elegant.

And that isn’t the end. There are other smaller issues that deter me. For instance, WPF does not have Fluid UI like SL4, so there is no clean approach to adding natural animations to your data collections. I was hopeful that Blend’s FluidMoveBehavior would fill the gap, but I haven’t been able to get it working even in the most simple scenarios. Also, the WPF toolkit is in a sad state right now, with no updates since 9 months ago (aside from the Ribbon control). Silverlight is definitely getting more attention in this arena.

I really want to harness the power of WPF, but at this point it feels like Silverlight makes it much easier of an experience for developing LOB applications. With that said, I am still going to forge ahead and give my best shot at trying to make WPF work. But if I had to make a recommendation now, I would say that developers in similar circumstances should go for Silverlight first, while always keeping a hawk’s eye on performance. If your application isn’t doing a ton of CRUD on a remote data source, and thus validation and RIA Services aren’t necessary, then WPF becomes an easier sell.

In the event that I do make some breakthroughs with WPF, I’ll be sure to update this post. Stay tuned…