What Is Data Binding

Data binding is a solution to a problem that developers used to solve over and over in user-interface applications. In the past, if you wanted to present data to a user, you had to retrieve the data from where it was stored and get it into your application. You then had to write custom code to render the data with graphics, or you could manually populate properties on controls with the data to display it. The way that you approached this would be different for each situation, each type of data, and each type of presentation that you provided. If the user was allowed to interact with the data and make modifications or additions to it through the user interface, you had to write custom code to collect the modified values from the user interface and push them back into the underlying data objects or collections in memory. You also needed code that persisted the changed values to the data store from which it came. This required a lot of repetitive and error-prone code, which always cries out for a better solution. Figure 1.1 depicts this process.

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Figure 1.1. Data-Binding Process

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Data binding encapsulates all of these steps into components that help present the data, which reduces the amount of code that you need to write. Some of that code goes into the data-bound controls that present the data, and some of it goes into nonvisual components that make data binding easier (this is described in detail in Chapters 79).

Data binding also involves providing easy-to-understand patterns for how you write code to hook up data to controls for presentation and editing. Finally, it involves developer tools that help write the code for you, using intuitive design-time interactions provided by Visual Studio 2005. The overall process of presenting and editing data is still basically the same as when no data binding is involved, but using data binding significantly reduces the amount and complexity of the code you have to write.

Data binding has been around in various forms in different environments since early versions of tools like Visual Basic, FoxPro, and Delphi. Many early attempts at data binding left a lot to be desiredthey either exposed too many details to the programmer, provided inconsistent or unreliable behavior to the user, or were just too complicated to use and understand. Data-binding capabilities have been part of the .NET Framework for both Windows Forms and ASP.NET Web forms since version 1.0 of each. The data-binding capabilities of Windows Forms controls in .NET 1.0 and 1.1 were a big improvement over previous environments, but they still fell short in many situations. Significant improvements have been made in Windows Forms 2.0, making it both quicker and easier to get data-bound applications up and running.

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