Part I of this book taught the details of how to use the Crystal Reports embedded designer to create professional reports. When a report is complete, its design and layout stays the same every time it was run. The data that it prints will change, but the report format is locked. With Crystal Reports .NET, reports have the flexibility to be dynamic. .NET programmers have full access to the properties of a report and the underlying report objects. These properties can be read and many of them can be overridden. You get the power to create a reporting solution that takes user input and customizes each report prior to printing it. This can range from changing the formatting of report objects, modifying the grouping and sorting, and changing the data source. The more you learn about runtime customization, the more you will find out what you can do. This chapter serves as the foundation for building your knowledge throughout the rest of the book.
The reason why you have so much power to modify reports is because .NET treats every report as an object-oriented class. The entire object model is exposed to your .NET program. Whether you program with VB.NET or C# isn’t important. The object model can be accessed by any of the .NET languages.
There are three ways to use the Crystal Reports object model. The first is to use the ReportDocument class. It is the most powerful because it references virtually every class and property of the report. The second way is to use the methods and properties of the CrystalReportViewer control. When compared to the ReportDocument class, the viewer only has a small subset of properties and methods. The viewer lets you modify the properties that affect logging in to a data source, setting report parameters, and deciding which report to preview. The last way to work with the object model is to subscribe to the events that are triggered while the report is previewed and printed. These events are useful for knowing what part of the report is being looked at and what the user is doing. This chapter goes into detail on all three ways of customizing reports during runtime.
