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The components can be repeated to introduce leading zeros as padding. Listing 22-8 contains a demonstration. Listing 22-8. Repeating Format Components using System;

Conditional compilation allows you to mark a section of source code to be either compiled or skipped, depending on whether a particular compilation symbol is defined. There are four directives for specifying conditional compilation: #if #else #elif #endif A condition is a simple expression that returns either true or false. A condition can consist of a single compilation symbol or an expression of symbols and operators, as summarized in Table 23-2. Subexpressions can be grouped with parentheses. The literals true and false can also be used in conditional expressions.

Tracking references allow more options for returning information from a method or function, in addition to using the return value. Since a function can only have one return value, this is useful. In classic C++, you might have used a pointer to a pointer to return a pointer to allocated memory. Similarly, in C++/CLI, you can use a tracking reference to a handle to return a handle to an object that is allocated within a method or function. The code in Listing 4-12 shows the use of a tracking reference to a handle. This technique allows the handle to be modified in the function and retain its new value outside the function. Listing 4-12. Using a Tracking Reference void Query(String^ search, Recordset^% records) { // Query the database, generate recordset, // and set the records handle to point to it. records = gcnew Recordset(); } The function would be called as in Listing 4-13. Listing 4-13. Calling a Function with Tracking References static Recordset^ PlantQuery(String^ search) { DBConnection connection; Recordset^ records; connection.Query( search, records ); return records; } This example is a very typical use of tracking references. Without the tracking reference, you could change the object in the function and have those changes preserved, but you would not be able to make the handle reference a different object entirely or assign it to a newly created object.

The last part of Listing 30-1 is enumerating the results. In keeping with other forms of LINQ, LINQ to Entities doesn t execute the query until you enumerate the result. In Listing 30-1, I enumerate the results using a foreach loop and print the value of the FirstName and LastName properties to the console: foreach (Employee e in result) { Console.WriteLine("Name: {0} {1}", e.FirstName, e.LastName); }

MainForm has a StatusStrip control at the bottom, so the user can be informed about any longrunning activity that is occurring. Also, when a long-running activity is going on, the mouse cursor should be changed to indicate that the application is busy.

(The fully qualified strong name of your assembly)