Operators
Many of the C# operators are supported by the built-in types, and allow you to perform basic operations with values of those types. C# objects like DateTime, and TimeSpan (which you met in the previous section) must be programmed with behaviour that is appropriate to a specific operator
The operators can be grouped as follows
Arithmetic operators
Are divided into two groups, binary and unary operators.
Binary operators being +, - , /, *, and %,
Always used as follows - <left operand> <operator> <right operand>
Expression | Result |
|---|---|
3 + 4 | 7 |
var1 - 3.142 * 2 | Assuming var1 has a value 10, the result would be 3.716 |
But what if we wanted to subtract 3.142 from var1 first then multiply the result by 2? C# arithmetic operators obey the laws of precedence. *, /, and % always execute before + and - operators. We can change the precedence using parenthesis.
Expression | Result |
|---|---|
(var1 - 3.142) * 2 | Assuming var1 has a value of 10, the result would be 13.716 |
Unary operators being ++, --, -, !, ~, sizeof, and (type)*
For ++ and – (the increment and decrement operators; respectively)
Can be used as follows
Usage | Result |
|---|---|
<variable>++ | Will print 10 11
|
++<variable> | Will print 11 11
|
<variable>-- | Will print 10 9
|
--<variable> | Will print 9 9
|
-<variable> | Will print 10 -10 |
Unary minus can be used as follows
Usage | Result |
|---|---|
-<variable> or -<value> | Will print 10 -10 |
-( -<variable>)) or -( -<value>)) | Will print 10 -10 10 |
Comparison operators
These are < (less than), > (greater than), <= (less than or equal), and >= (greater than or equal) comparisons. They may be used with char, integral, and floating point types.
These operators always result in a TRUE or FALSE.
These operators may be used as follows
Usage | Result |
|---|---|
Will print
But we know that is incorrect | |
Will print
But we know this is incorrect |
In the two examples above, both logic expressions could be valid. The error is in the output statements.
Think carefully about the intended resultant logic after each logic expression
Boolean logical operators
Unary logical operator
NOT (logical negation) operator, used to reverse a logic value. It produces true if the value is false, and false if the value is true.
Usage | Result |
|---|---|
!variable or !<value> | Will print true false |
Binary logical operators
The binary logical operators have this form: <left operand> <logical operator> <right operand>
The left and right hand operands must be boolean values. Boolean values can be direct boolean values or the result of an expression that results in a boolean value
These operators always result in a TRUE or FALSE.
Usage | Result |
|---|---|
Will print
The && (AND) operator can only result in true if both the lh and rh are true 
| |
Will print
The && operator is known as a short circuit operator. If the lh is false, then the rh expression is not evaluated | |
Will print
A single & means that both lh and rh expressions will be evaluated even if the lh is false | |
Will print
The || (OR) operator will result in true if any of the following conditions are met 
| |
Will print
The || operator is known as a short circuit operator. If the lh is true, then the rh expression is not evaluated | |
Will print
A single | means that both lh and rh expressions will be evaluated even if the lh is true |
Equality operators
The == (equality) and != (inequality) operators check the left and right hand operands are equal or not equal, respectively
The == operator returns true if the lh and rh operands equal.
The != operator returns true if the lh and rh operands are NOT equal.
These operators always result in a TRUE or FALSE.
Working with built-in types
Usage | Result |
|---|---|
Will print
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| Will print
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String Equality
Two strings are considered to be equal when they are both null, or of the same length and contain identical characters (their ASCII encodings are the same)
Usage | Result |
|---|---|
Will print
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| Will print
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