C# 0 The Complete Reference

PART I

C h a p t e r   1 8 :  

G e n e r i c s  

533

PART IPART I

The output is shown here:

2  4  6  8  10

13.4  15.4  17.4  19.4  21.4

0,0,0  2,2,2  4,4,4  6,6,6  8,8,8

There are several things of interest in the preceding example. First, notice how 

ISeries

 is 

declared:

public interface ISeries {

As mentioned, a generic interface uses a syntax similar to that of a generic class.

Now, notice how 

ByTwos

, which implements 

ISeries

, is declared:

class ByTwos : ISeries {

The type parameter 

T

 is specified by 

ByTwos

 and is also specified in 

ISeries

. This is 

important. A class that implements a generic version of a generic interface must, itself, be 

generic. For example, the following declaration would be illegal because 

T

 is not defined:

class ByTwos : ISeries { // Wrong!

The type argument required by the