Wrox Professional Crystal Reports for Visual Studio NET Second Edition phần 3 ppsx

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Chapter 2

Special Field Name Description

Record Number An internal, sequential record number assigned to all records

returned to the report

Page Number Page number

Group Number An internal, sequential number assigned to all groups

Total Page Count The total page count

Report Title The report title, as saved in the report file’s Summary

Information

Report Comments The comments entered in the Summary Information

Record Selection Formula The Record Selection Formula used by the report

Group Selection Formula The group selection formula used by the report

File Path and Name The full path and filename of the report file

File Author The author of the report from the report file’s Summary

Information

File Creation Date The date the report file was created

Page N of M Where N is the current page and M is the total page count

Summary Fields

Earlier in the chapter, we looked at creating a report using the Standard Expert. One of the tabs in the

expert was for Total, where a summary field could be inserted into your report. Summary fields are

usually associated with groups or a grand total in your report and can be inserted into your report by

right-clicking anywhere within the Report Designer and selecting Insert → Summary from the menu

that appears. This opens the dialog shown in Figure 2-27.

At this point, you may also notice that the right-click menu includes an option for Subtotal; subtotals

and summary fields are similar, but a subtotal refers specifically to a sum, whereas a summary field

could be a sum, an average, or a standard deviation.

Formula Fields

Crystal Reports .NET features a rich formula language that has evolved over the years as a powerful

way to add complex calculations to reports. Formula fields appear in curly braces and are prefixed by

the @ symbol; a formula used within another formula would look like this:

{@SalesTax} + {@InvoiceTotal}

Formula fields are created using the integrated Formula Editor. To see the editor, right-click Formula

Fields in the Field Explorer, select New, enter a name, and then click OK to open the dialog shown in

Figure 2-28.

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Figure 2-27

Figure 2-28

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When working with formula fields, you have a choice of two different types of syntax: Crystal Syntax or

Basic Syntax. If you have worked with Crystal Reports before, you will probably be familiar with Crystal

Syntax. It was the original formula language available with Crystal Reports and is still used for Record

Selection Formulas and conditional formatting.

Basic Syntax was introduced to eliminate the need to learn a second formula syntax. The syntax, func￾tions, and control structures are similar to Visual Basic, which many developers are familiar with, and it

is easy for developers to create formulas using a language that is familiar to them.

Which language you use depends on what facet of Crystal Reports you are working with. As I mentioned

earlier, the record and group selection formulas within Crystal Reports are written using Crystal Syntax

exclusively, so you are going to have to learn a little bit anyway. For formulas that will appear on your

report, you have a choice of using either Crystal or Basic Syntax. (You can’t mix the two in one formula,

but you can mix the two different types of formulas in one report.) A drop-down list in the Formula

Editor controls the syntax, and you can switch between the two if required.

Formulas are covered in length in Chapter 8, “Formulas and Logic,” but keep in mind you may see

the Formula Editor appear in other places throughout this book; it is also used to create Record Selection

Formulas and perform conditional formatting, among other things.

Parameter Fields

Parameter fields within Crystal Reports .NET are used to prompt the user to enter information when the

report is run. Parameters can be used in a number of different ways, from simple data entry (like enter￾ing the name of a user to be displayed on the report) to record selection (to filter the content of a report).

Parameter fields are designated using curly braces and are prefixed by a question mark, so a parameter

field in use in a formula might look something like this:

If {?EnterCountry} = “USA” then “North America”

To insert a parameter field into your report, right-click the Parameter Fields section of the Field Explorer

and select New, which will open the dialog shown in Figure 2-29.

Figure 2-29

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