Add External-Marshalling Attributes for Structs

The Visual Basic Upgrade Companion is able to add marshalling information to the structures used in WIN-API calls. These extra attributes allows the resulting .NET code to keep coherency with most of the legacy behavior found on the unmanaged code of the WIN API dlls.

Original VB6 Code

Type
Private Type ACTYLG_TYPE
    lFirstField              As Long         ' <Force proper alignment>
    lIDN                     As Long         ' INTEGER NOT NULL
    sCNCRCY_USER_IDN         As String * 8   ' CHAR (8) NOT NULL
    sTABLE_ALIAS_NAME        As String * 6   ' CHAR (6) NOT NULL
    iTABLE_UNQ_IDN_NI        As Integer      ' <Null Indicator>
    lTABLE_UNQ_IDN           As Long         ' INTEGER
    iTABLE_UNQ_SEQ_NUM_NI    As Integer      ' <Null Indicator>
    iTABLE_UNQ_SEQ_NUM       As Integer      ' SMALLINT
End Type

Resulting .NET Code:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
private struct ACTYLG_TYPE
{
    public int lFirstField; // <Force proper alignment>
    public int lIDN; // INTEGER NOT NULL
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 8)] 
private char[] _sCNCRCY_USER_IDN; // CHAR (8) NOT NULL
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 6)] 
private char[] _sTABLE_ALIAS_NAME; // CHAR (6) NOT NULL
    public short iTABLE_UNQ_IDN_NI; // <Null Indicator>
    public int lTABLE_UNQ_IDN; // INTEGER
    public short iTABLE_UNQ_SEQ_NUM_NI; // <Null Indicator>
    public short iTABLE_UNQ_SEQ_NUM; // SMALLINT

    public string sCNCRCY_USER_IDN
    {
        set { Utils.CopyValToArray(value, _sCNCRCY_USER_IDN, 8); }
        get { return new String(_sCNCRCY_USER_IDN); }
    }
    public string sTABLE_ALIAS_NAME
    {
        set { Utils.CopyValToArray(value, _sTABLE_ALIAS_NAME, 6); }
        get { return new String(_sTABLE_ALIAS_NAME); }
    }

    public static ACTYLG_TYPE CreateInstance()
    {
        ACTYLG_TYPE result = new ACTYLG_TYPE();
        result._sCNCRCY_USER_IDN = new char[8];
        result._sTABLE_ALIAS_NAME = new char[6];
        return result;
    }
}