Part II: Basic C# Programming in C#.NET

Generate Code-128 in C#.NET Part II: Basic C# Programming

C# defines the assignment operator shorthand as follows:

Even that s not good enough C# provides this even shorter version:

All three of the preceding statements are equivalent they all increment n by 1 The increment operator is strange enough, but believe it or not, C# has two increment operators: ++n and n++ The first one, ++n, is called the preincrement operator, while n++ is the postincrement operator The difference is subtle but important Remember that every expression has a type and a value In the following code, both ++n and n++ are of type int:

int n = int n = int n; 1; p = ++n; 1; m = n++;

But what are the resulting values of m and p (Hint: The choices are 1 or 2) The value of p is 2, and the value of m is 1 That is, the value of the expression ++n is the value of n after being incremented, while the value of the expression n++ is the value of n before it is incremented Either way, the resulting value of n is 2 Equivalent decrement operators that is, n-- and --n exist to replace n = n 1 These work in exactly the same way as the increment operators

C# also provides a set of logical comparison operators, as shown in Table 4-3 These operators are called logical comparisons because they return either a true or a false of type bool

4: Smooth Operators Table 4-3

Operator Is True If a has the same value as b a is greater than b a is greater than or equal to b a is less than b a is less than or equal to b a is not equal to b

Here s an example that involves a logical comparison:

int m = 5; int n = 6; bool b = m > n;

This example assigns the value false to the variable b because 5 is not greater than 6 The logical comparisons are defined for all numeric types, including float, double, decimal, and char All the following statements are legal:

2; > 20; > b ; < a ; < b ; > 12M;

// // // // // //

true true false - alphabetically later = greater true - upper A is less than lower a true - all upper are less than all lower false

The comparison operators always produce results of type bool The comparison operators other than == are not valid for variables of type string (Not to worry; C# offers other ways to compare strings)

Comparing two floating values can get dicey, and you need to be careful with these comparisons Consider the following comparison:

3; (3 * f2) == f1; 3; (3 * f2) == f1;

Notice that the fifth and eighth lines in the preceding example each contain first an assignment operator (=) and then a logical comparison (==) These are different animals C# does the logical comparison and then assigns the result to the variable on the left The only difference between the calculations of b1 and b2 is the original value of f1 So, what are the values of b1 and b2 The value of b2 is clearly true: 9 / 3 is 3; 3 * 3 is 9; and 9 equals 9 Voil ! The value of b1 is not so obvious: 10 / 3 is 3333 3333 * 3 is 9999 Is 9999 equal to 10 That depends on how clever your processor and compiler are On a Pentium or later processor, C# is not smart enough to realize that b1 should be true if the calculations are moved away from the comparison You can use the system absolute value function to compare f1 and f2 as follows: