28 September, 2008

Strongly typed data binding in Windows Forms

Windows Forms data binding is a great tool for model-view-style applications, where the connection between the model and its view is easily declared. However, data binding is also an error-prone and tedious process with no IntelliSense support where properties are specified as strings.

Tired of the need of looking up property names when you declare data bindings? Sick of mistyping a property name when you bind and not discovering the mistake until you run your application? Have a look at Strongbind.

Strongbind vs traditional data binding

Traditional data binding is typically declared like this:
Obviously, several errors can arise from this declaration: Your control may not have a Text property, or you might have spelled it wrong. The same goes the Description property of your source.

The same declaration in Strongbind is written as follows:

As you probably understand, the risk of mistyping is removed, and we get IntelliSense support out of the box.

Behind the scenes of Strongbind

To achieve this strongly typed data binding, Strongbind uses a technique known as proxying. Strongbind dynamically generates a proxy for your business object and your control, and uses the proxies to intercept the calls to the property getters during runtime to declare the data binding. Hence, you need to declare a bindable source and bindable target first to create the proxies, and then use these proxies during the binding declaration. You will get a runtime error if you try to use your real objects when declaring data bindings.

Limitations of Strongbind

Although Strongbind makes data binding a far more declarative process, the library does have its limitations.

Controls containing ActiveX components are not supported. If the control containing an ActiveX component is a custom control created by you, you can get around it by declaring an interface for
the control and specifying that as the type to use when declaring your binding source:

Also, binding to concrete binding sources with non-virtual properties is not supported. Again, the recommended workaround is to create an interface for your binding source and use that when declaring the data bindings. (You always want to create these interfaces, since decoupling your objects' interfaces from their implementation is recommended for testability, maintainability, and is generally A Good Thing(tm).)

Apart from these two issues, which can be worked around in most cases, Strongbind should work flawlessly. If it does not, please let me know.

Where do I get it?

Strongbind is an open source project hosted at Github. To get the latest version, check out the code from its repository.

Strongbind is still in an early development stage, so no releases have been created yet. I still encourage you to check out and start using the library as soon as possible, though. A beta will be released as soon as I feel comfortable doing it.

If you want to contribute to Strongbind, I happily welcome you to do so.

Bind away!

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