DOCUMENT:Q175979 11-JAN-2001 [vbwin] TITLE :PRB: All Parameters of Choose Function Are Evaluated PRODUCT :Microsoft Visual Basic for Windows PROD/VER:WINDOWS:4.0,5.0,6.0 OPER/SYS: KEYWORDS:kbGrpDSVB ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Visual Basic Learning Edition for Windows, version 6.0 - Microsoft Visual Basic Professional Edition for Windows, version 6.0 - Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 - Microsoft Visual Basic Control Creation Edition for Windows, version 5.0 - Microsoft Visual Basic Learning Edition for Windows, version 5.0 - Microsoft Visual Basic Professional Edition for Windows, version 5.0 - Microsoft Visual Basic Enterprise Edition for Windows, version 5.0 - Microsoft Visual Basic Standard Edition for Windows, version 4.0 - Microsoft Visual Basic Professional Edition for Windows, version 4.0 - Microsoft Visual Basic Enterprise Edition for Windows, version 4.0 ------------------------------------------------------------------------------- SYMPTOMS ======== When you specify functions as the Choice arguments in a Choose function, all functions are executed. CAUSE ===== The Choose function allows you to select a value from a list of choices based on the value passed as the index. For example, the following statement would result in x being assigned the value "b": x = Choose(2, "a", "b", "c") The parameters passed to the Choose function do not need to be static values as in the above example. You can use function names instead: x = Choose(2, MyFunction1(), MyFunction2(), MyFunction3()) In this situation, all of the functions referenced are executed regardless of the index specified. In this example, the functions MyFunction1, MyFunction2, and MyFunction3 are all executed even though the result of MyFunction2 is the value returned by Choose. Choose is implemented as a function with a parameter array and every parameter must be evaluated before it can be passed to the Choose function. Visual Basic's implementation of the Choose function can be duplicated with the following function: Public Function MyChoose(Index As Single, ParamArray Choice()) On Error GoTo BadChoice If IsObject(Choice(Index - 1)) Then Set MyChoose = Choice(Index - 1) Else MyChoose = Choice(Index - 1) End If Exit Function BadChoice: MyChoose = Null End Function RESOLUTION ========== Because this behavior is by design, another approach must be taken to avoid all parameters being evaluated. The logic of the Choose function can easily be broken down into an equivalent "If...Then...ElseIf" statement or a "Select Case" statement. Sample Choose Statement ----------------------- result = Choose(MyIndex, MyFunction1(), MyFunction2(), MyFunction3()) Equivalent 'If...Then...ElseIf' Statement ----------------------------------------- If MyIndex = 1 Then result = MyFunction1() ElseIf MyIndex = 2 Then result = MyFunction2() ElseIf MyIndex = 3 Then result = MyFunction3() Else result = Null End If Equivalent 'Select Case' Statement ---------------------------------- Select Case MyIndex Case 1 result = MyFunction1() Case 2 result = MyFunction2() Case 3 result = MyFunction3() Case Else result = Null End Select STATUS ====== This behavior is by design. MORE INFORMATION ================ Steps to Reproduce Behavior --------------------------- 1. Create a new Visual Basic project. Form1 is created by default. 2. Add a Command button to Form1. 3. Add the following code to Form1: Option Explicit Private Function MyFunction1() As Long Debug.Print "MyFunction1" MyFunction1 = 1 End Function Private Function MyFunction2() As Long Debug.Print "MyFunction2" MyFunction2 = 2 End Function Private Function MyFunction3() As Long Debug.Print "MyFunction3" MyFunction3 = 3 End Function Private Sub Command1_Click() Dim result result = Choose(2, MyFunction1(), MyFunction2(), MyFunction3()) End Sub 4. Save and run the project. 5. Click the CommandButton. Note that the "Debug.Print" statements from the three user-defined functions are executed even though the result of MyFunction2 is the returned value. REFERENCES ========== Visual Basic's Online Help for the Choose function. Additional query words: kbVBp500 kbVBp600 kbVBp kbdsd kbDSupport kbVBp400 kbVBA ====================================================================== Keywords : kbGrpDSVB Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500Search kbVBA500 kbVBA600 kbVB500 kbVB600 kbVB400Search kbVB400 kbZNotKeyword3 Version : WINDOWS:4.0,5.0,6.0 Issue type : kbprb ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 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