17: Reflection and Attributes in C#.NET

Encode PDF-417 2d barcode in C#.NET 17: Reflection and Attributes
17: Reflection and Attributes
Make PDF-417 2d Barcode In C#.NET
Using Barcode encoder for .NET framework Control to generate, create PDF-417 2d barcode image in Visual Studio .NET applications.
catch (ArgumentException ) { success = false; errorMessage = stringFormat( "The option '{0}' is " + "invalid for '{1}'", optionParts[1], option); } } else { success = false; errorMessage = stringFormat( "Data type '{0}' on {1} is not" + " supported", propertyPropertyTypeToString(), commandLineGetType()ToString()); } } else { success = false; errorMessage = stringFormat( "Option '{0}' is not supported", option); } } } return success; } }
Creating Barcode In C#.NET
Using Barcode maker for VS .NET Control to generate, create barcode image in VS .NET applications.
Although Listing 173 is long, the code is relatively simple Main() begins by instantiating a CommandLineInfo class This type is defined specifically to contain the command-line data for this program Each property corresponds to a command-line option for the program where the command line is as shown in Output 172
Generating PDF417 In VS .NET
Using Barcode drawer for ASP.NET Control to generate, create PDF 417 image in ASP.NET applications.
OUTPUT 172:
Create PDF-417 2d Barcode In VS .NET
Using Barcode maker for .NET Control to generate, create PDF417 image in .NET applications.
Compressexe /Out:<file name> /Help /Priority:RealTime|High|AboveNormal||Normal|BelowNormal|Idle
Making PDF-417 2d Barcode In VB.NET
Using Barcode drawer for VS .NET Control to generate, create PDF417 image in .NET framework applications.
Reflection
Bar Code Generator In C#
Using Barcode creation for .NET Control to generate, create bar code image in Visual Studio .NET applications.
The CommandLineInfo object is passed to the CommandLineHandler s TryParse() method This method begins by enumerating through each option and separating out the option name (Help or Out, for example) Once the name is determined, the code reflects on the CommandLineInfo object, looking for an instance property with the same name If the property is found, it assigns the property using a call to SetValue() and specifying the data corresponding to the property type (For arguments, this call accepts the object on which to set the value, the new value, and an additional index parameter that is null unless the property is an indexer) This listing handles three property types: Boolean, string, and enum In the case of enums, you parse the option value and assign the property the text s enum equivalent Assuming the TryParse() call was successful, the method exits and the CommandLineInfo object is initialized with the data from the command line Interestingly, in spite of the fact that CommandLineInfo is a private class nested within Program, CommandLineHandler has no trouble reflecting over it and even invoking its members In other words, reflection is able to circumvent accessibility rules as long as appropriate code access security (CAS) permissions are established If, for example, Out was private, it would still be possible for the TryParse() method to assign it a value Because of this, it would be possible to move CommandLineHandler into a separate assembly and share it across multiple programs, each with its own CommandLineInfo class In this particular example, you invoke a member on CommandLineInfo using PropertyInfoSetValue() Not surprisingly, PropertyInfo also includes a GetValue() method for retrieving data from the property For a method, however, there is a MethodInfo class with an Invoke() member Both MethodInfo and PropertyInfo derive from MemberInfo (although indirectly), as shown in Figure 171 The CAS permissions are set up to allow private member invocation in this case because the program runs from the local computer, and by default, locally installed programs are part of the trusted zone and have appropriate permissions granted Programs run from a remote location will need to be explicitly granted such a right
Encode Barcode In C#
Using Barcode creator for VS .NET Control to generate, create barcode image in .NET framework applications.
17: Reflection and Attributes
ANSI/AIM Code 39 Printer In Visual C#.NET
Using Barcode generation for .NET framework Control to generate, create Code 39 image in .NET applications.
Figure 171: MemberInfo Derived Classes
Creating Code 128A In Visual C#.NET
Using Barcode generator for .NET Control to generate, create Code 128B image in .NET framework applications.
Reflection on Generic Types Just as you can use reflection on nongeneric types, the 20 framework included provisions for reflecting on generic types Runtime reflection on generics determines whether a class or method contains a generic type, and any type parameters or arguments it may contain Determining the Type of Type Parameters
Making Data Matrix In Visual C#.NET
Using Barcode printer for .NET Control to generate, create Data Matrix 2d barcode image in VS .NET applications.
In the same way that you can use a typeof operator with nongeneric types to retrieve an instance of SystemType, you can use the typeof operator on type parameters in a generic type or generic method Listing 174
Data Matrix 2d Barcode Drawer In .NET Framework
Using Barcode generation for ASP.NET Control to generate, create Data Matrix 2d barcode image in ASP.NET applications.
Reflection
Draw Barcode In Visual Basic .NET
Using Barcode generator for VS .NET Control to generate, create barcode image in .NET applications.
applies the typeof operator to the type parameter in the Add method of a Stack class
UPC-A Supplement 2 Printer In .NET
Using Barcode generation for ASP.NET Control to generate, create Universal Product Code version A image in ASP.NET applications.
Listing 174: Declaring the Stack<T> Class
Bar Code Printer In VS .NET
Using Barcode drawer for .NET Control to generate, create barcode image in .NET applications.
public class Stack<T> { public void Add(T i) { Type t = typeof(T); } }
Encode Bar Code In Java
Using Barcode maker for Java Control to generate, create bar code image in Java applications.
Once you have an instance of the Type object for the type parameter, you may then use reflection on the type parameter itself to determine its behavior and tailor the Add method to the specific type more effectively
Scanning Barcode In Java
Using Barcode scanner for Java Control to read, scan read, scan image in Java applications.
Generating Code 3/9 In Visual Basic .NET
Using Barcode maker for Visual Studio .NET Control to generate, create Code 39 Extended image in .NET applications.
Scan EAN 13 In Visual Studio .NET
Using Barcode scanner for VS .NET Control to read, scan read, scan image in VS .NET applications.