qr code generator c# example a b B a is is is is an A an A because it is derived from A a B an object in C#.NET

Drawing QR-Code in C#.NET a b B a is is is is an A an A because it is derived from A a B an object

a b B a is is is is an A an A because it is derived from A a B an object
Make Quick Response Code In C#
Using Barcode creation for .NET Control to generate, create Quick Response Code image in .NET applications.
Scanning QR Code ISO/IEC18004 In C#.NET
Using Barcode decoder for Visual Studio .NET Control to read, scan read, scan image in Visual Studio .NET applications.
Most of the is expressions are self-explanatory, but two may need a little discussion First, notice this statement:
Printing Barcode In C#.NET
Using Barcode printer for VS .NET Control to generate, create barcode image in .NET framework applications.
Bar Code Reader In Visual C#.NET
Using Barcode recognizer for .NET Control to read, scan read, scan image in .NET framework applications.
if(b is A) ConsoleWriteLine("b is an A because it is derived from A");
Denso QR Bar Code Maker In Visual Studio .NET
Using Barcode maker for ASP.NET Control to generate, create Denso QR Bar Code image in ASP.NET applications.
Printing QR Code In .NET Framework
Using Barcode printer for Visual Studio .NET Control to generate, create QR Code ISO/IEC18004 image in .NET framework applications.
The if succeeds because b is an object of type B, which is derived from type A Thus, b is an A However, the reverse is not true When this line is executed,
QR Code Generator In Visual Basic .NET
Using Barcode encoder for .NET Control to generate, create QR Code image in Visual Studio .NET applications.
Data Matrix 2d Barcode Creation In C#.NET
Using Barcode creation for Visual Studio .NET Control to generate, create Data Matrix 2d barcode image in VS .NET applications.
if(a is B) ConsoleWriteLine("This won t display -- a not derived from B");
Make Code 3/9 In C#
Using Barcode generator for .NET Control to generate, create Code-39 image in .NET framework applications.
Print Matrix 2D Barcode In Visual C#
Using Barcode generation for .NET Control to generate, create 2D Barcode image in VS .NET applications.
the if does not succeed, because a is of type A, which is not derived from B Thus, a is not B
Painting Linear 1D Barcode In Visual C#.NET
Using Barcode drawer for VS .NET Control to generate, create Linear Barcode image in VS .NET applications.
Code 9/3 Printer In C#.NET
Using Barcode creation for VS .NET Control to generate, create Code 9/3 image in .NET framework applications.
Using as
Making EAN / UCC - 13 In Objective-C
Using Barcode encoder for iPad Control to generate, create UCC.EAN - 128 image in iPad applications.
Drawing Bar Code In Java
Using Barcode encoder for Java Control to generate, create bar code image in Java applications.
Sometimes you will want to try a conversion at runtime, but not throw an exception if the conversion fails (which is the case when a cast is used) To do this, use the as operator, which has this general form: expr as type
Bar Code Drawer In None
Using Barcode generation for Software Control to generate, create barcode image in Software applications.
GS1 DataBar-14 Generation In .NET Framework
Using Barcode maker for .NET Control to generate, create GS1 DataBar Expanded image in Visual Studio .NET applications.
17:
Painting Bar Code In Objective-C
Using Barcode generation for iPhone Control to generate, create bar code image in iPhone applications.
Making UCC-128 In VS .NET
Using Barcode drawer for .NET framework Control to generate, create GS1 128 image in .NET framework applications.
R u n t i m e Ty p e I D , R e f l e c t i o n , a n d A t t r i b u t e s
Barcode Generator In VS .NET
Using Barcode maker for Reporting Service Control to generate, create bar code image in Reporting Service applications.
Data Matrix ECC200 Creation In None
Using Barcode generator for Software Control to generate, create DataMatrix image in Software applications.
Here, expr is the expression being converted to type If the conversion succeeds, then a reference to type is returned Otherwise, a null reference is returned The as operator can be used to perform only reference, boxing, unboxing, or identity conversions The as operator offers a streamlined alternative to is in some cases For example, consider the following program that uses is to prevent an invalid cast from occurring:
// Use is to avoid an invalid cast using System; class A {} class B : A {} class CheckCast { static void Main() { A a = new A(); B b = new B(); // Check to see if a can be cast to B if(a is B) // if so, do the cast b = (B) a; else // if not, skip the cast b = null; if(b==null) ConsoleWriteLine("The cast in b = (B) a is NOT allowed"); else ConsoleWriteLine("The cast in b = (B) a is allowed"); } }
PART I PART I PART I
This program displays the following output:
The cast in b = (B) a is NOT allowed
As the output shows, since a is not a B, the cast of a to B is invalid and is prevented by the if statement However, this approach requires two steps First, the validity of the cast must be confirmed Second, the cast must be made These two steps can be combined into one through the use of as, as the following program shows:
// Demonstrate as using System; class A {} class B : A {} class CheckCast { static void Main() { A a = new A(); B b = new B(); b = a as B; // cast, if possible
Part I:
The C# Language
if(b==null) ConsoleWriteLine("The cast in b = (B) a is NOT allowed"); else ConsoleWriteLine("The cast in b = (B) a is allowed"); } }
Here is the output, which is the same as before:
The cast in b = (B) a is NOT allowed
In this version, the as statement checks the validity of the cast and then, if valid, performs the cast, all in one statement
Using typeof
Although useful in their own ways, the as and is operators simply test the compatibility of two types Often, you will need to obtain information about a type To do this, C# supplies the typeof operator It retrieves a SystemType object for a given type Using this object, you can determine the type s characteristics The typeof operator has this general form: typeof(type) Here, type is the type being obtained The Type object returned encapsulates the information associated with type Once you have obtained a Type object for a given type, you can obtain information about it through the use of various properties, fields, and methods defined by Type Type is a large class with many members, and a discussion is deferred until the next section, where reflection is examined However, to briefly demonstrate Type, the following program uses three of its properties: FullName, IsClass, and IsAbstract To obtain the full name of the type, use FullName IsClass returns true if the type is a class IsAbstract returns true if a class is abstract
// Demonstrate typeof using System; using SystemIO; class UseTypeof { static void Main() { Type t = typeof(StreamReader); ConsoleWriteLine(tFullName); if(tIsClass) ConsoleWriteLine("Is a class"); if(tIsAbstract) ConsoleWriteLine("Is abstract"); else ConsoleWriteLine("Is concrete"); } }
This program outputs the following:
Copyright © OnBarcode.com . All rights reserved.