Visual Basic Helper Routines
Pure VB: Determine if a Control is a Member of a Control Array
     
Posted:   Wednesday January 15, 2003
Updated:   Monday December 26, 2011
     
Applies to:   VB4-32, VB5, VB6
Developed with:   VB6, Windows XP
OS restrictions:   None
Author:   VBnet - Randy Birch, Rick Rothstein
     

Related:  

CopyMemory: Determining Array Initialization State and Dimensions
     
 Prerequisites
None.

Another Simple is Good example, this time a one-line function that returns True if the passed control is a member of a control array, or False if it is not, and without requiring error trapping.

VB's TypeName property returns a string representing the type of control specified, i.e. pass it a single (non-array) control Text1 and you get "TextBox". But when TypeName is passed the name of any control that is a member of a control array VB does not return its specific control type but instead returns the TypeName "Object". Simple assignment in a wrapper function creates a Boolean value to differentiate between control arrays and non-arrayed controls.

Note: the method expects the 'raw' control named passed. For example, if you have a command button array named Command1(), you would pass the object Command1 as the parameter to the function to receive the correct True response. Were you to pass an actual reference to a particular member of that control array (i.e. Command(3) ), the function correctly returns False as to that function Command(3) is a specific, identifiable control (just as non-arrayed controls are).

Place the IsControlInArray() function into a form (or module), declare Public or Private as appropriate, and pass as shown below.

 BAS Module Code
None.

 Form Code
To the form, add a command button (Command1), an option button (Option1) and a second option button as Option2 with its Index property set to 0 to create a control array. Add the following code:

Option Explicit
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Copyright 1996-2011 VBnet/Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Distribution: You can freely use this code in your own
'               applications, but you may not reproduce 
'               or publish this code on any web site,
'               online service, or distribute as source 
'               on any media without express permission.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Public Function IsControlInArray(ctl As Object) As Boolean

   IsControlInArray = TypeName(ctl) = "Object"

End Function


Private Sub Command1_Click()

   Print IsControlInArray(Option1)    'non-array
   Print IsControlInArray(Option2)    'array
   Print IsControlInArray(Option2(0)) 'array member   
   Print IsControlInArray(Command1)   'non-array   

End Sub
 Comments
If you created the form with the controls indicated in the Form Code instructions above, executing the command click code will return :

   False   'control passed is not an array
   True    'control passed is an array
   False   'control passed is not an array; although each control is an array member Option2(0) is not an array.
   False   'control passed is not an array


 
 

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