Problem Passing Byte-Array to a Class's Property

[Ben321]

The property is defined in the class with this code:

Public Property Let PrivateKey(ByRef Prk() As Byte)

The code in a command button defines an array to pass with this code:

Dim PrKey(39) As Byte

and then passes it to the class's property with this code:

RSA.PrivateKey = PrKey()

What am I doing wrong? Or is this a bug in VB6 itself?

[dilettante]

This is not a "bug in VB6" but an attempt to violate a COM rule.

You cannot really have an array Property. If there is a fault in the VB6 compiler it is that this doesn't get flagged on the Property definition in the Class but on attempts to use it.

You have to either use a method call or else you'll need to pass some sort of object type that wraps the array. The easiest way to do this and get auto-coercion is to make these Variant type properties and add type checking logic if required. For example:

RSA.cls

Option Explicit

Private mPrk() As Byte

Public Property Get PrivateKey() As Variant
    PrivateKey = mPrk
End Property

Public Property Let PrivateKey(ByVal Prk As Variant)
    If VarType(Prk) <> (vbArray Or vbByte) Then Err.Raise 5
    mPrk = Prk
End Property

Form1.frm

Option Explicit

Private Sub Command1_Click()
    Dim PrKey(39) As Byte
    
    PrKey(1) = 255
    With New RSA
        .PrivateKey = PrKey
        MsgBox .PrivateKey(1)
    End With
End Sub