Operators and Comparisons

Comparison operators

Module Program
    Sub Main()
        Console.WriteLine(5 = 5)
        Console.WriteLine(5 <> 3)
        Console.WriteLine(5 > 3)
        Console.WriteLine(5 <= 3)
    End Sub
End Module

True
True
True
False

= means comparison inside an expression and assignment in a statement like x = 5. "Not equal" is <>.

Logical operators

Module Program
    Function Check(label As String, result As Boolean) As Boolean
        Console.WriteLine($"  checking {label}")
        Return result
    End Function

    Sub Main()
        Console.WriteLine("And:")
        Console.WriteLine(Check("a", False) And Check("b", True))
        Console.WriteLine("AndAlso:")
        Console.WriteLine(Check("a", False) AndAlso Check("b", True))
        Console.WriteLine("OrElse:")
        Console.WriteLine(Check("a", True) OrElse Check("b", True))
        Console.WriteLine(Not True)
        Console.WriteLine(True Xor True)
    End Sub
End Module

And:
  checking a
  checking b
False
AndAlso:
  checking a
False
OrElse:
  checking a
True
False
False

• AndAlso and OrElse short-circuit: the right side is skipped when the left side already decides the answer. Use them in conditions.
• And, Or, and Xor always evaluate both sides; on integers they are bitwise operators (6 And 3 is 2).

Short-circuiting protects you from errors:

Module Program
    Sub Main()
        Dim name As String = Nothing
        If name IsNot Nothing AndAlso name.Length > 3 Then
            Console.WriteLine("long name")
        Else
            Console.WriteLine("no name or short name")
        End If
    End Sub
End Module

no name or short name

With And, name.Length would run even though name is Nothing, and throw a NullReferenceException.

Is, IsNot, TypeOf, and Like

Module Program
    Sub Main()
        Dim a As Object = "text"
        Dim b As Object = Nothing

        Console.WriteLine(b Is Nothing)
        Console.WriteLine(a IsNot Nothing)
        Console.WriteLine(TypeOf a Is String)
        Console.WriteLine("report2025.txt" Like "report####.txt")
        Console.WriteLine("Visual Basic" Like "V*c")
    End Sub
End Module

True
True
True
True
True

Is compares references (is it the same object, or Nothing?). Like does simple wildcard matching: * any text, ? one character, # one digit.

The If operator

If(condition, a, b) returns a or b — VB's conditional expression. If(value, fallback) returns fallback when value is Nothing:

Module Program
    Sub Main()
        Dim age = 20
        Console.WriteLine(If(age >= 18, "adult", "minor"))

        Dim nickname As String = Nothing
        Console.WriteLine(If(nickname, "(no nickname)"))
    End Sub
End Module

adult
(no nickname)

Operator precedence

From highest to lowest: ^, unary -, * /, \, Mod, + -, &, comparisons, Not, And/AndAlso, Or/OrElse, Xor. When in doubt, add parentheses.