C# 0 The Complete Reference

ISeries

,

ByTwos

, and 

SeriesDemo

 in the compilation. The compiler will automatically compile all three files to 

create the final executable. For example, if you called these files 

ISeries.cs

,

ByTwos.cs

, and 

SeriesDemo.cs

, then the following command line will compile the program:

>csc SeriesDemo.cs ISeries.cs ByTwos.cs

If you are using the Visual C++ IDE, simply add all three files to your C# project. One other 

point: It is perfectly valid to put all three of these classes in the same file, too.

The output from this program is shown here:

Next value is 2

Next value is 4

Next value is 6

Next value is 8

Next value is 10

Resetting

Next value is 2

Next value is 4

Next value is 6

Next value is 8

Next value is 10

Starting at 100

Next value is 102

Next value is 104

Next value is 106

Next value is 108

Next value is 110

It is both permissible and common for classes that implement interfaces to define 

additional members of their own. For example, the following version of 

ByTwos

 adds 

the method 

GetPrevious( )

, which returns the previous value:

// Implement ISeries and add GetPrevious().

 class ByTwos : ISeries {

  int start;

  int val;

  int prev;

  public ByTwos() {

    start = 0;

    val = 0;

    prev = -2;

  }

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