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6. Move your playhead out to 1 second and rotate the UserControl back to its original position,

invoked, just as a regular delegate would be. Compiling and running the code in Listing 10-17 products the following results: Result: 200 Press enter to finish We didn t have to define a custom delegate in this example. The System.Action type handled everything for us. There are 17 different Action implementations available. Starting with the one used in Listing 10-17, each adds a new generic parameter. This is not as confusing as it may sound; you just create the generic implementation that matches the number of parameters the target method required. Listing 10-18 contains an example that uses two parameters. Listing 10-18. Using a Generic Action Delegate using System; class Calculator { public void CalculateProduct(int x, int y) { // perform the calculation int result = x * y; // print out a message with the result Console.WriteLine("Result: {0}", result); } } class Listing 18 { static void Main(string[] args) { // create a new instance of Calculator Calculator calc = new Calculator(); // create an action and assign a method Action<int, int> act = calc.CalculateProduct; // invoke the method via the Action act(10, 20); // wait for input before exiting Console.WriteLine("Press enter to finish"); Console.ReadLine(); } } In this example, the method I want to delegate has two int parameters, so I used the Action<int, int> delegate (the parameter types for an Action need not all be the same). If I had wanted to delegate a

The Border is a very simple layout element that allows you to draw a Stroke around another element and then give it a Background or an actual border. The Border layout element can only have one child element, and that content can be either left, right, top, bottom, or center aligned. These properties can be set manually in the XAML, or in Blend in the Layout section of the Properties panel. Try making a Border element now:

Figure 13-1. The member constants of an enum are represented by underlying integral values. You can assign enum values to variables of the enum type. For example, the following code shows the declaration of three variables of type TrafficLight. Notice that you can assign member literals to variables, or you can copy the value from another variable of the same type. class Program { static void Main() { Type Variable Member TrafficLight t1 = TrafficLight.Red; TrafficLight t2 = TrafficLight.Green; TrafficLight t3 = t2; Console.WriteLine(t1); Console.WriteLine(t2); Console.WriteLine(t3); } } This code produces the following output. Notice that the member names are printed as strings. Red Green Green

10. Click OK. The EF designer will now have added this function to the context where it can be accessed as follows (note you could then move this into your entity using partial classes): var crew = ctx.GetCrewInfo(1);

One of the nice features of Web Forms is that the now-familiar system of properties and events is used. In this section, we ll configure the controls by changing the value of properties. I ll be briefer in my instructions since you will be an old hand at editing properties by now.

There are many types of applications for which this is important. For instance, order entry applications typically have extensive defaulting of values based on the customer. Inventory management applications often have many default values for specific parts, based on the product family to which the part belongs. Medical records also often have defaults based on the patient and physician involved. When the Create() method of the DataPortal is invoked, it s passed a criteria object. As I ve explained, the data portal will either use reflection against the criteria object or will rely on the type information in CriteriaBase to determine the type of business object to be created. Using that information, the data portal uses reflection to create an instance of the business object itself. However, this is a bit tricky because all business objects have private or protected constructors to prevent direct creation by code in the UI: [Serializable] public class Employee : BusinessBase<Employee> { private Employee() { /* prevent direct creation */ } } Business objects will expose static factory methods to allow the UI code to create or retrieve objects. Those factory methods will invoke the client-side DataPortal. (I discuss this class-in-charge concept earlier in the chapter.) As an example, an Employee class may have a static factory method, such as the following: public static Employee NewEmployee() { return DataPortal.Create<Employee>(); } Notice that no Employee object is created on the client here. Instead, the factory method asks the client-side DataPortal for the Employee object. The client-side DataPortal passes the call to the serverside data portal. If the data portal is configured to run remotely, the business object is created on the server; otherwise, the business object is created locally on the client. Even though the business class has only a private constructor, the server-side data portal uses reflection to create an instance of the class. The alternative is to make the constructor public, in which case the UI developer will need to learn and remember that they must use the static factory methods to create the object. Making the constructor private provides a clear and direct reminder that the UI developer must use the static factory method, thus reducing the complexity of the interface for the UI developer. Keep in mind that not implementing the default constructor won t work either, because in that case, the compiler provides a public default constructor on your behalf. Once the server-side data portal has created the business object, it calls the business object s DataPortal_Create() method, optionally passing a criteria object as a parameter. At this point, code inside the business object is executing, so the business object can do any initialization that s appropriate for a new object. Typically, this will involve going to the database to retrieve any configurable default values. When the business object is done loading its defaults, the server-side data portal returns the fully created business object back to the client-side DataPortal. If the two are running on the same machine, this is a simple object reference; but if they re configured to run on separate machines, the business object is serialized across the network to the client (i.e., it s passed by value), so the client machine ends up with a local copy of the business object. The UML sequence diagram in Figure 2-16 illustrates this process.

The relational and equality comparison operators are binary operators that compare their operands and return a value of type bool. These operators are listed in Table 8-8. The relational and equality operators are binary and left-associative. Table 8-8. The Relational and Equality Comparison Operators

to add a line of code, EXEC NULL, after the second INSERT. This is because SQL*Plus does not retrieve and display the DBMS_OUTPUT information after a failed DML statement in those releases. In Oracle 10g and above it does.