10.1. Operators and their precedence in C#
| Higher precedence | |
|---|---|
| Operator category | Operators |
| Primary | x.y f(x) a[x] x++ x-- new typeof checked unchecked |
| Unary | + – ! ~ ++x --x (T)x |
| Multiplicative | * / % |
| Additive | + - |
| Shift | << >> |
| Relational and type testing | < > <= >= is as |
| Equality | == != |
| Logical AND | & |
| Logical XOR | ^ |
| Logical OR | | |
| Conditional AND | && |
| Conditional OR | || |
| Conditional (ternary) | ?: |
| Assignment | = *= /= %= += -= <<= >>= &= ^= |= |
All operators in the same category have the same precedence. To decide which operator in a particular group takes precedence, follow these associative rules:
except for the assignment operators, all other binary operators are left associative – for example, a+b-c is the same as (a+b)-c;
the assignment operators and conditional (ternary) operator are right associative – for example, if a, b, and c are non-boolean variables of the same type, a=b=c is the same as a=(b=c)[1];
[1] The value of c is assigned to b. This is followed by the value of b being assigned to a.
you can use brackets to enforce precedence. [2]
[2] Please do use brackets to make your codes look clearer if you are using multiple operators in a single expression. Expressions containing many operators are very difficult to read and, if there are no brackets to specify precedence, it becomes necessary to refer to the precedence table.
Each operator is described in Table 10.2:
| Category | Operator | Comments |
|---|---|---|
| Primary | x.y | Dot operator [1] Used to specify the member of an object/class – x is the object, y is the member |
| f(x) | Used to list the arguments or parameters to a method – f is the method name, and x represents the method parameter(s) | |
| a[x] | Used to index an array or an C# indexer (see Chapter 21) | |
| x++ | Post increment operator Same as Java | |
| x-- | Post decrement operator Same as Java | |
| new | new operator Used to create an instance of a class – besides being an operator keyword, note that the new keyword can also be used as a modifier in C# for name hiding (see section 7.11) | |
| typeof | typeof operator Returns the System.Type object representing the type of the object it is applied to – similar to java.lang.Object's getClass() method | |
| checked | checked operator Control overflow checking for mathematical operations – no equivalent in Java | |
| unchecked | unchecked operator Control overflow checking for mathematical operations – no equivalent in Java | |
| Unary | + | Unary plus Same as Java – example: +3 |
| - | Unary minus Same as Java – example: -3 | |
| ! | (Boolean) logical negation operator
Only to be used on boolean values – returns true or false only. Same as Java's ! operator | |
| ~ | Bitwise complement operator
Only to be used on the following C# simple types – int, uint, long, ulong. Same as Java's ~ operator | |
| ++x | Prefix increment operator Same as Java | |
| --x | Prefix decrement operator Same as Java | |
| (T)expression | Cast operator
Used to explicitly cast an expression into another type – T denotes the new type. Same as Java | |
| Multiplicative | * | Mathematical multiplication (also used for dereferencing pointers in unsafe codes) Same as Java |
| / | Mathematical integral division Same as Java | |
| % | Mathematical remainder (modulus) Same as Java | |
| Additive | + | Mathematical addition (binary add) Same as Java |
| - | Mathematical subtraction (binary minus) Same as Java | |
| Shift | << | (Bitwise) Left-shift operator Same as Java |
| >> | (Bitwise) Right-shift operator [2] Same as Java | |
| Relational and type testing | < | Smaller-than operator Same as Java |
| > | Bigger-than operator Same as Java | |
| <= | Smaller-than or equals operator Same as Java | |
| >= | Bigger-than or equals operato Same as Java | |
| is | is operator Used to check if an object is of a particular type – similar to Java's instanceof operator | |
| as | as operator Can be viewed as a combination of the is operator and a cast – no equivalent in Java | |
| Equality | == | Equality operator Slightly different from Java's == when used to compare string objects – otherwise very similar to Java's == operator |
| != | Inequality operator Because the == operator behaves slightly differently in C# and Java, the != operator, which returns the complementary result of the == operator is also different – returns the complementary result of the == operator | |
| Bitwise/boolean AND | & | &-operator Like Java, can be used for both bool (boolean AND) and integral (bitwise AND) types |
| Bitwise/boolean XOR | ^ | XOR operator Like Java, can be used for both bool (boolean AND) and integral (bitwise AND) types |
| Bitwise/boolean OR | | | | operator Like Java, can be used for both bool (boolean AND) and integral (bitwise AND) types |
| Conditional AND (also known as short-circuit boolean AND) | && | Conditional & operator Similar to Java's && operator – will only evaluate second operand if first operand is true. Like Java's &&, this operator applies only for bool types (not for integral types) |
| Conditional OR (also known as short-circuit boolean OR) | || | Conditional | operator Similar to Java's || operator – will not evaluate second operand if first operand is true. Like Java's ||, this operator applies only for bool types (not for integral types) |
| Conditional | ?: | Conditional operator Only operator which requires three operands (hence, also popularly known as the 'ternary operator') – same as Java's ternary operator |
| Assignment [3] | = | Assignment operator Same as Java |
| *= | Multiplication assignment operator Same as Java | |
| /= | (Integral) Division assignment operator Same as Java | |
| %= | Remainder assignment operator Same as Java | |
| += | Addition assignment operator Same as Java | |
| -= | Subtraction assignment operator Same as Java | |
| <<= | Left shift assignment operator Same as Java | |
| >>= | Right shift assignment operator Same as Java | |
| &= | AND assignment operator Same as Java | |
| ^= | XOR assignment operator Same as Java | |
| |= | OR assignment operator Same as Java | |
| Additional C# operators used for unsafe code (see Chapter 29): | ||
| Operators for unsafe coding | * | Pointer operator Used to declare pointer types and for dereferencing pointers (same symbol is used as the mathematical multiplication operator) – no equivalent in Java |
| & | Address of operator Used to retrieve the address of a particular object (same symbol is used as the bitwise and boolean AND operator) – no equivalent in Java | |
| sizeof | sizeof operator Returns the size (number of bytes) of a simple type or other structs – no equivalent in Java | |
| - | Member-of operator Used for accessing a member of a class via pointers, like the . operator – Can only be applied to a pointer type. No equivalent in Java | |
[1] C++'s :: (class reference operator) has been removed from C#. Use the dot operator instead to refer to a class member.
[2] C# has no >>> operator.
[3] The current implementation of C# converts code like j+=2; into more efficient MSIL codes than j=j+2;. Hence if possible, use +=, -=, /=, etc. in your codes.