How to write 2 statements that differ just by Operator type in VB.NET

Question

Hi

I have the following code sample, where the only difference between the 2 parts of the If statement is the less than/greater than operators.

Is there a better way to write this? Could almost do with being able to define an Operator variable.

        If myVar = true Then

            Do While (X < Y)
                'call Method A
                'the values of X and Y will change within this loop
            Loop

        Else

            Do While (X > Y)
                'call Method A
                'the values of X and Y will change within this loop
            Loop

        End If

thanks

Answer 1

Do While ((myVar And X < Y) Or (Not myVar And X > Y))
    ' call Method A
Loop

Answer 2

You can use the ternary conditional operator, If, as of VB 2008:

Do While (If(myVar, X < Y, X > Y)))
    'call Method A
Loop

However, this will check myVar on every iteration instead of just once, which is bad for performance.

Answer 3

Dim from As Integer = CInt(iif(myVar, x, y))
Dim until As Integer = CInt(iif(myVar, y, x))

While from < until
    'call Method A
End While

Or if 2008 or newer, as Samir says, use the ternary conditional operator to avoid the CInt casts.

Answer 4

You can use a delegate:

Public Function LessThan(Of T As IComparable)(ByVal A As T, ByVal B As T) As Boolean
    Return A.CompareTo(B) < 0
End Function

Public Function GreaterThan(Of T AS IComparable)(ByVal A As T, ByVal B As T)  As Boolean
    Return A.CompareTo(B) > 0
End Function

---

Dim comparer As Func(Of Integer,Integer,Boolean) = AddressOf GreaterThan(Of Integer)
If myVar Then comparer = AddressOf LessThan(Of Integer)

Do While comparer(X,Y)
    ''#call Method A
    ''#the values of X and Y will change within this loop
Loop

---

Of course, that needs VS2008. For more fun:

Do While CBool(Y.CompareTo(Y) * -1) = myVar
    ''#...
End While