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Maker PDF417 in visual C#.net Basic Design Goals

If you run the page, you ll notice that the Label control updates every four seconds with the new time without doing a full page refresh (see Figure 5-13).

Temporary tables can be useful in an application where you need to temporarily store a set of rows to be processed against other tables, for either a session or a transaction. They are not meant to be used as a means to take a single larger query and break it up into smaller result sets that would be combined back together (which seems to be the most popular use of temporary tables in other databases). In fact, you will find in almost all cases that a single query broken up into smaller temporary table queries performs more slowly in Oracle than the single query would have. I ve seen this behavior time and time again, when given the opportunity to rewrite the series of INSERTs into temporary tables as SELECTs in the form of one large query, the resulting single query executes much faster than the original multi-step process.

} } } This code produces the following output before being terminated after about 5 seconds: Timer started. Processing timer Processing timer Processing timer Processing timer

You can also create and populate an array before the method call, and pass the single array variable as the actual parameter. In this case, the compiler uses your array, rather than creating one. For example, the following code uses method ListInts, declared in the previous example. In this code, Main creates an array and uses the array variable as the actual parameter, rather than using separate integers. static void Main() { int[] MyArr = new int[] { 5, 6, 7 }; MyClass mc = new MyClass(); mc.ListInts(MyArr); foreach (int x in MyArr) Console.WriteLine("{0}", x); } This code produces the following output: 50 60 70

Microsoft purchased and integrated the Dundas ASP.NET charting controls in early 2008. This set contains over 35 different types of charts and a huge amount of functionality, some of which is shown in Figure 10-7. Previously these controls had to be installed as an add-on and a number of settings added to Web.config. ASP.NET 4.0, however, includes these controls, and it is no longer necessary to make changes to Web.config to include them.

Since System::Object acts as the lowest common denominator of almost all .NET types, there are certain similarities to void*, which is the lowest common denominator of all C++ pointer types. However, System::Object is much more powerful than void*. System::Object provides a set of methods that is available for all expressions resulting in .NET types. These methods are as follows: ToString: This is a virtual function that returns a string that represents the object. The default implementation provided by System::Object simply returns the name of the object s type. Many types in the FCL provide an overload for this function. For example, System::Enum, the base class of all managed enums, overloads ToString so that the string literal of the current value is returned. The ToString overload of System::String simply returns the string value. GetType: This function is the entry point to the very powerful runtime type information features of .NET. Using this method, you can obtain a .NET object that allows the investigation of almost any static aspect of a managed type. Starting from the type s identity, name, and characteristics, all its type members can be inspected down to the level of method implementations. Furthermore, types can be instantiated and invoked dynamically based on runtime type information objects. GetHashCode: As the name says, GetHashCode is supposed to return a hash code of the object. Like ToString, it is a virtual function. The FCL has a couple of collection classes that internally use this function. Equals: Various collection classes in the FCL use Object::Equals for search operations. Notice that if you override Equals, you must override GetHashCode, too. However, both methods should only be overridden for types whose instances are immutable by definition. Some collection classes in the FCL expect that two objects that are equal have the same hash code. Furthermore, the value that GetHashCode returns for an object is expected to remain unchanged, even if the object s data changes. Unless a type is implemented so that its instances are immutable, it is impossible to provide nontrivial overrides for GetHashCode and Equals so that both requirements are met. Neither C++/CLI, C#, nor VB .NET map the == operation to Object::Equals.

You can use a number of modifier keywords in a method definition to change the behavior. The modifier that you will use most frequently is an access modifier, which determines how your method can be used. Table 9-2 lists the access modifiers for methods. For information on the other kinds of modifier available, see the Using Method Modifiers section later in the chapter. Table 9-2. Access Modifiers for Methods

// Console::WriteLine("Resolution of desktop: {0} x {1}", pixelsX , pixelsY); ldstr "Resolution of desktop: {0} x {1}" ldloc.1 box [mscorlib]System.Int32 ldloc.0 box [mscorlib]System.Int32 call void [mscorlib]System.Console::WriteLine(string, object, object) // return 0; ldc.i4.0 ret } Due to the .locals section at the beginning of main, the runtime will allocate 24 bytes on the stack for the three variables: 4 bytes for each of the two integers pixelsX and pixelsY, and 16 bytes for the variable rect. To pass the address of the rect variable, the ldloca instruction (load a local variable s address) is used: call ldloca call valuetype HWND__* GetDesktopWindow() rect int32 GetWindowRect(valuetype HWND__*, valuetype tagRECT*)