BUG: Choose Function Incorrectly Uses Option Base Setting

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0

SYMPTOMS

A Visual Basic program using the Choose function incorrectly returns the wrong value if the program sets the Option Base to a 1.

WORKAROUND

The following are the ways to work around this issue:

1. Add 1 to the index argument.

2. Create the following function in a module. Copy the following code to the code window of the module:

         Option Explicit
   

         'This function will be used in place of the built in Choose function
         'and this takes the setting of Option Base into account.
   

         Public Function Choose(i As Integer, ParamArray a())
            Choose = a(i + LBound(a) - 1)
         End Function
   
   

STATUS

Microsoft has confirmed this to be an issue in the Microsoft products listed at the beginning of this article. Microsoft is researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

The following creates a program to reproduce this behavior. A command button displays the results of the Choose function in the Debug window. When you set the Option Base to 1, the Choose function incorrectly returns a Null value.

Steps to Reproduce Behavior

1. Start Visual Basic 4.0, or if it is already running, click New Project on the File menu.

2. Add a Command button to the Form1 form.

3. Copy the following code to the Code window of the Form1 form:

         Option Explicit
   

         'Comment the next line to work around this behavior
         Option Base 1
   

         Private Sub Command1_Click()
            Debug.Print Choose(1, "Index 1a", "Index 1b", "Index 1c")
            Debug.Print Choose(2, "Index 2a", "Index 2b", "Index 2c")
            Debug.Print Choose(3, "Index 3a", "Index 3b", "Index 3c")
         End Sub
   
   

4. On the Run menu, click Start or press the F5 key to start the program. Click the Command button. The Debug window displays, "Null" and "b." The correct values should be "a" and "b."