544: Declaring a Field as readonly in Visual C#

Creation PDF-417 2d barcode in Visual C# 544: Declaring a Field as readonly
Listing 544: Declaring a Field as readonly
PDF417 Maker In Visual C#.NET
Using Barcode generator for Visual Studio .NET Control to generate, create PDF-417 2d barcode image in VS .NET applications.
class Employee { public Employee(int id) { Id = id; } //
Barcode Printer In Visual C#.NET
Using Barcode printer for .NET Control to generate, create bar code image in .NET framework applications.
public readonly int Id;
Encode PDF417 In VS .NET
Using Barcode creation for ASP.NET Control to generate, create PDF417 image in ASP.NET applications.
public void SetId(int newId) {
PDF-417 2d Barcode Creator In Visual Studio .NET
Using Barcode creator for .NET Control to generate, create PDF 417 image in .NET framework applications.
5: Classes
Making PDF-417 2d Barcode In Visual Basic .NET
Using Barcode drawer for .NET Control to generate, create PDF 417 image in .NET framework applications.
// ERROR: read-only fields cannot be set // outside the constructor // Id = newId; } // }
Print Bar Code In C#.NET
Using Barcode creator for Visual Studio .NET Control to generate, create bar code image in .NET applications.
Unlike constant fields, readonly fields can vary from one instance to the next In fact, a readonly field s value can change from its value during declaration to a new value within the constructor Furthermore, readonly fields occur as either instance or static fields Another key distinction is that you can assign the value of a readonly field at execution time rather than just at compile time Using readonly with an array does not freeze the contents of the array It freezes the number of elements in the array because it is not possible to reassign the readonly field to a new instance However, the elements of the array are still writeable
Make Barcode In Visual C#.NET
Using Barcode creation for .NET Control to generate, create barcode image in .NET framework applications.
Nested Classes
Painting Code 39 Extended In C#.NET
Using Barcode generation for .NET framework Control to generate, create Code 39 Extended image in .NET applications.
In addition to defining methods and fields within a class, it is also possible to define a class within a class Such classes are nested classes You use a nested class when the class makes little sense outside the context of its containing class Consider a class that handles the command-line options of a program Such a class is generally unique to each program and there is no reason to make a CommandLine class accessible from outside the class that contains Main() Listing 545 demonstrates such a nested class
Code 128 Code Set B Generation In Visual C#.NET
Using Barcode printer for .NET Control to generate, create USS Code 128 image in VS .NET applications.
Listing 545: Defining a Nested Class
Draw Data Matrix 2d Barcode In Visual C#
Using Barcode creation for .NET Control to generate, create Data Matrix image in Visual Studio .NET applications.
class Program { // Define a nested class for processing the command line private class CommandLine
Create Barcode In Java
Using Barcode generation for Java Control to generate, create barcode image in Java applications.
public CommandLine(string[] arguments) { for(int argumentCounter=0; argumentCounter<argumentsLength; argumentCounter++)
Data Matrix Maker In VB.NET
Using Barcode creation for .NET Control to generate, create Data Matrix image in VS .NET applications.
Nested Classes
Bar Code Printer In .NET
Using Barcode creator for ASP.NET Control to generate, create barcode image in ASP.NET applications.
{ switch (argumentCounter) { case 0: Action = arguments[0]ToLower(); break; case 1: Id = arguments[1]; break; case 2: FirstName = arguments[2]; break; case 3: LastName = arguments[3]; break; } } } public public public public } static void Main(string[] args) { CommandLine commandLine = new CommandLine(args); switch (commandLineAction) { case "new": // Create a new employee // break; case "update": // Update an existing employee's data // break; case "delete": // Remove an existing employee's file // break; default: ConsoleWriteLine( "Employeeexe " + "new|update|delete <id> [firstname] [lastname]"); break; } } }
Decode Code 128A In Visual Studio .NET
Using Barcode scanner for .NET Control to read, scan read, scan image in Visual Studio .NET applications.
string string string string
Code 128C Creator In .NET Framework
Using Barcode printer for ASP.NET Control to generate, create Code 128 Code Set B image in ASP.NET applications.
Action; Id; FirstName; LastName;
Code 39 Extended Maker In Visual Basic .NET
Using Barcode generation for .NET Control to generate, create Code39 image in .NET applications.
5: Classes
Universal Product Code Version A Generator In .NET Framework
Using Barcode generation for ASP.NET Control to generate, create UPC A image in ASP.NET applications.
The nested class in this example is ProgramCommandLine As with all class members, no containing class identifier is needed from inside the containing class, so you can simply refer to it as CommandLine One unique characteristic of nested classes is the ability to specify private as an access modifier for the class itself Because the purpose of this class is to parse the command line and place each argument into a separate field, ProgramCommandLine is relevant only to the Program class in this application The use of the private access modifier defines the intended scope of the class and prevents access from outside the class You can do this only if the class is nested The this member within a nested class refers to an instance of the nested class, not the containing class One way for a nested class to access an instance of the containing class is if the containing class instance is explicitly passed, such as via a constructor or method parameter Another interesting characteristic of nested classes is that they can access any member on the containing class, including private members The converse to accessing private members is not true, however It is not possible for the containing class to access a private member on the nested class Nested classes are rare
Create Code 128A In Visual Basic .NET
Using Barcode generator for .NET framework Control to generate, create Code 128B image in .NET framework applications.
Language Contrast: Java Inner Classes
USS Code 39 Scanner In .NET
Using Barcode scanner for .NET framework Control to read, scan read, scan image in Visual Studio .NET applications.
Java includes not only the concept of a nested class, but also the concept of an inner class Inner classes correspond to objects that are associated with the containing class instance rather than just a syntactic relationship In C#, you can achieve the same structure by including an instance field of a nested type within the class
Make Barcode In .NET
Using Barcode creation for .NET framework Control to generate, create barcode image in .NET applications.