Not Operator (Visual Basic)
Performs logical negation on a Boolean expression, or bitwise negation on a numeric expression.
Syntax
result = Not expression
Parts
result
Required. Any Boolean or numeric expression.
expression
Required. Any Boolean or numeric expression.
Remarks
For Boolean expressions, the following table illustrates how result is determined.
If expression is |
The value of result is |
|---|---|
True |
False |
False |
True |
For numeric expressions, the Not operator inverts the bit values of any numeric expression and sets the corresponding bit in result according to the following table.
If bit in expression is |
The bit in result is |
|---|---|
| 1 | 0 |
| 0 | 1 |
Note
Since the logical and bitwise operators have a lower precedence than other arithmetic and relational operators, any bitwise operations should be enclosed in parentheses to ensure accurate execution.
Note that if Not someStr?.Contains("some string") or any other value that evaluates as Boolean? has the value of nothing or HasValue=false, the else block is run. The evaluation follows the SQL evaluation where null/nothing doesn't equal anything, not even another null/nothing.
Data Types
For a Boolean negation, the data type of the result is Boolean. For a bitwise negation, the result data type is the same as that of expression. However, if expression is Decimal, the result is Long.
Overloading
The Not operator can be overloaded, which means that a class or structure can redefine its behavior when its operand has the type of that class or structure. If your code uses this operator on such a class or structure, be sure you understand its redefined behavior. For more information, see Operator Procedures.
Example 1
The following example uses the Not operator to perform logical negation on a Boolean expression. The result is a Boolean value that represents the reverse of the value of the expression.
Dim a As Integer = 10
Dim b As Integer = 8
Dim c As Integer = 6
Dim firstCheck, secondCheck As Boolean
firstCheck = Not (a > b)
secondCheck = Not (b > a)
The preceding example produces results of False and True, respectively.
Example 2
The following example uses the Not operator to perform logical negation of the individual bits of a numeric expression. The bit in the result pattern is set to the reverse of the corresponding bit in the operand pattern, including the sign bit.
Dim a As Integer = 10
Dim b As Integer = 8
Dim c As Integer = 6
Dim firstPattern, secondPattern, thirdPattern As Integer
firstPattern = (Not a)
secondPattern = (Not b)
thirdPattern = (Not c)
The preceding example produces results of –11, –9, and –7, respectively.
