如何編寫2個語句，這些語句在VB.NET中僅由操作符類型區分

Question

我有以下代碼示例，其中If語句的2個部分之間的唯一區別是小於/大於運算符。

有沒有更好的方法來寫這個？幾乎可以做到定義一個Operator變量。

 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 

感謝

Answer 1

可以使用三元條件操作，If，截至2008年VB的：

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

然而，這將在每次迭代檢查myVar，而不是隻有一次，這對性能不利。

Answer 2

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

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 

或者如果2008年或更新，如Samir所說，使用三元條件運算符來避免CInt投。

Answer 4

您可以使用委託：

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 

---

當然，需要VS2008。更多的樂趣：

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