In this scenario you will finish out your study of data binding by looking at how to facilitate two-way communication between the object and the form so that updates in either are reflected in the other. This approach is the one that you will end up using in the majority of cases, as it facilitates the two way communication between the object and GUI controls. As you saw in the previous example, using only one way communication, basically from the form to the object, could result in inconsistencies when the object is updated outside of the form. In order to enable two way communication, you need to let the data binding mechanism know when your objects properties have changed. The code for this solution appears in the "TwoWayDataBindingSolution".
When you define a binding between a control's property and the data source's property, the binding mechanism automatically looks for the event named propertyChanged on the data source. If found, the binding mechanism provides a handler for this event to receive notice when that property's value changes. Therefore, if you implement property changed events on your Employee's properties, you should be able to easily enable two way data binding.
Figure 16 illustrates the code changes to the variable declaration section of the Employee class to declare the needed events. Figure 17 illustrates the raising of the event on the property set function.
Figure 16
Figure 17
Since the object is now able to communicate changes back to the form, you can tie the Save button enabled property to the isDirty property of the object. This will have the effect of only enabling the Save button when the object has changed data that needs to be saved. The code to accomplish this is shown in Figure 18.
Figure 18
Summary
The .NET framework provides a rich set of functionality for data binding. It has come a long way from data binding within the earlier Microsoft toolset. In this article you looked at various levels of data binding from a completely manual approach to bidirectional communication between controls and properties on custom objects. Along the way you also looked at how you can tap into the event model of the data binding mechanisms provided by the .NET framework in order to override the default formatting behavior.
About the Author
Luther Stanton is a Principal Consultant with Intellinet Corporation, headquartered in the Atlanta, GA. Intellinet, the southeast's only five-time Microsoft Gold Certified Partner, provides application-development and infrastructure consulting services. Intellinet builds enterprise .NET systems using object-oriented development techniques and their custom process, a best-of-breed development methodology combining the leading agile techniques in the business.
Luther resides in Locust Grove, Georgia, with his wife, Heidi. He has actively developed Microsoft-centric applications for over eight years and has worked with .NET for three years. Luther's current focus is on methodology deployment and enterprise architecture consulting and implementation. Luther can be reached at luthers@intellinet.com.
Proposion N2N connects Microsoft .NET applications to Lotus Notes and Lotus Domino databases. This ADO.NET managed data provider allows you to perform blindingly fast queries and updates of Notes data from ASP.NET pages, .NET web services, Windows, or Mobile applications. An innovative SQL-like query language leverages the unique features of Notes and makes collaborative software accessible to relational database programmers.
Unlike text-based file formats image files aren't made up of words, which makes searching for an image file by keyword difficult. Instead of being able to simply open the file to see what it contains, we're stuck looking at the text around it and other metadata to determine the image's meaning. In this article, Ziran Sun shows you how to build a simple database-based image keyword system that allows you to associate keywords with images and use these keywords to make finding images easier. [Read This Article][Top]
In the second part of of his article on using MySQL with ASP.NET, Ziran Sun covers how to add a new MySQL user to the database server, assign the user the appropriate permissions, connect to the database, and build a simple ASP.NET page to perform a query. [Read This Article][Top]
Back in the days of classic ASP, if you were building a database-driven
web site, your choice was either to invest a lot of money to get a copy of Microsoft SQL Server
(or some other enterprise-ready database) or invest a lot of time finding a way to deal with the
performance and scalability limitations of Microsoft Access. Luckily these days there's
another viable alternative: MySQL. [Read This Article][Top]
Moving or copying a SQL Server database from one machine to another requires a lot of preparation in order to ensure a smooth transfer. In this article, Dina Fleet Berry examines the different methods and highlights the different issues associated with each of them. [Read This Article][Top]
There are many times when using SQL Server 2000 Query Analyzer to debug SQL statements is a better choice than debugging in Visual Studio .NET. In this article, Dina Fleet Berry explains why and walks you through the debugging process step-by step. [Read This Article][Top]
As a follow up to his article on retrieving objects from SQL Server using SQLXML and serialization, Gianluca Nuzzo discusses saving objects back to SQL Server using a schema definition file and updategrams. [Read This Article][Top]
One area that stands out when comparing ADO.NET 1.x to ADO.NET 2.0 is transaction processing. Bill Ryan shows just how easy transaction processing has become with the TransactionScope object in ADO.NET 2.0. [Read This Article][Top]
Developers often use brute force coding to marshal data between the GUI and application objects. In this article, Luther Stanton explains how to use .NET's out-of-the box data-binding functionality to make this job much easier. [Read This Article][Top]
Learn how to create a console application to queue a message in Microsoft Message Queuing (MSMQ) and then use an extended stored procedure to call the console application from a SQL Server trigger. [Read This Article][Top]
Connection pooling increases the performance of Web applications by reusing active database connections instead of creating a new connection with every request. This article shows how to monitor the connection pool, diagnose a potential problem, and apply the appropriate fix. [Read This Article][Top]
Mailing List Want to receive email when the next article is published? Just Click Here to sign up.
