Kasutaja:M2s17/RefVBDOTNET8

Operators

Comparison Operators

< - Less than comparison between 2 expressions

• true, if first expression is smaller than the second expression
• false, if first expression is greater than or equal to the second expression

<= - Less than or equal to comparison between 2 expressions

• true, if first expression is smaller than or equal to the second expression
• false, if first expression is greater than the second expression

> - Greater than comparison between 2 expressions

• true, if first expression is greater than the second expression
• false, if first expression is smaller than or equal to the second expression

>= - Greater than or equal to comparison between 2 expressions

• true, if first expression is greater than or equal to the second expression
• false, if first expression is smaller than the second expression

<> - inequality comparison between 2 expressions

• true, if first expression differs from the second expression
• false, on all other cases

= - equality comparison between 2 expressions

• true, if first expression value is the same as the second expression value
• false, on all other cases

Is - object reference comparison

• true, if the objects reference to the same object
• false, on all other cases

IsNot - object reference comparison

• false, if the objects reference to the same object
• true, on all other cases

TypeOf...Is - object variable comparison with a data type

• true, if thy are the same
• false, on all other cases

Like - string comparison with pattern

• true, if pattern exist
• false, on all other cases

Logical Operators

NOT - (boolean)performs logical negation

• true, if condition is false
• false, if condition is true

AND - (boolean)Performs a logical conjunction

• true, if both conditions are equal
• false, on all other cases

ANDALSO - (boolean)short circuited AND

• true, if both conditions are equal
• false, on all other cases

note : if the first expression is false, the other expression will never be evaluated

Or - (boolean)performs logical disjunction

• true, if at least of of the expressions is true
• false, if both expressions are false

OrAlso - (boolean)short circuited OR

• true, if at least of of the expressions is true
• false, if both expressions are false

note : if the first expression is true, the other expression will never be evaluated

Xor - (boolean)performs logical disjunction

• true, if expression differ
• false, if expression are equal(both true or both false)

IsFalse; IsTrue - Determines expression boolean value

note: you can not define only 1 of them, thy are a logical pair, and must be both declared if any

In addition

• if you use operators on numeric values rather then boolean, bitwise operation will be preformed
• reminder:

  a imp b = (not a) or b

  a eqw b = not (a xor b)

How To

String Manipulation

How To create string consisting of the specified number of spaces?

Dim specified_number as Byte = 4
Dim Test As String = Space(10)

Dim specified_number as Byte = 4
Dim Test As String = New String(" ", specified_number)

How To convert string to a number, type double?

Dim Test_string As String = "123.456"
Dim Test_double As Double = Ctype(Val(Test_string), double)

How To determine the length of a number in characters?

Dim Test As Integer = (123.456).ToString.Length

How To determine a possibly valid email?

Public Shared Function IsEmail(ByVal Email As String) As Boolean
   Dim re As New Regex("^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$")
   If re.IsMatch(Email) Then Return True Else Return False
End Function