C# WinApp ช่วยอธิบาย โค้ด นี้อย่างละเอียดหน่อยครับ

protected override CreateParams CreateParams {
            [SecurityPermission(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
            get {
                CreateParams cp = base.CreateParams;
                cp.ClassName = "COMBOBOX";
                cp.Style |= NativeMethods.WS_VSCROLL | NativeMethods.CBS_HASSTRINGS | NativeMethods.CBS_AUTOHSCROLL;
                cp.ExStyle |= NativeMethods.WS_EX_CLIENTEDGE;
                if (!integralHeight) cp.Style |= NativeMethods.CBS_NOINTEGRALHEIGHT;

                switch (DropDownStyle) {
                    case ComboBoxStyle.Simple:
                        cp.Style |= NativeMethods.CBS_SIMPLE;
                        break;
                    case ComboBoxStyle.DropDown:
                        cp.Style |= NativeMethods.CBS_DROPDOWN;
                        // Make sure we put the height back or we won't be able to size the dropdown!
                        cp.Height = PreferredHeight;
                        break;
                    case ComboBoxStyle.DropDownList:
                        cp.Style |= NativeMethods.CBS_DROPDOWNLIST;
                        // Comment above...
                        cp.Height = PreferredHeight;
                        break;
                }
                switch (DrawMode) {

                    case DrawMode.OwnerDrawFixed:
                        cp.Style |= NativeMethods.CBS_OWNERDRAWFIXED;
                        break;
                    case DrawMode.OwnerDrawVariable:
                        cp.Style |= NativeMethods.CBS_OWNERDRAWVARIABLE;
                        break;
                }

                return cp;
            }
        }

public const int SHGFI_ICON = 0x000000100  ,   // get icon
        SHGFI_DISPLAYNAME       = 0x000000200,     // get display name
        SHGFI_TYPENAME          = 0x000000400,     // get type name
        SHGFI_ATTRIBUTES        = 0x000000800,     // get attributes
        SHGFI_ICONLOCATION      = 0x000001000,     // get icon location
        SHGFI_EXETYPE           = 0x000002000,     // return exe type
        SHGFI_SYSICONINDEX      = 0x000004000,     // get system icon index
        SHGFI_LINKOVERLAY       = 0x000008000,     // put a link overlay on icon
        SHGFI_SELECTED          = 0x000010000,     // show icon in selected state
        SHGFI_ATTR_SPECIFIED    = 0x000020000,     // get only specified attributes
        SHGFI_LARGEICON         = 0x000000000,     // get large icon
        SHGFI_SMALLICON         = 0x000000001,     // get small icon
        SHGFI_OPENICON          = 0x000000002,     // get open icon
        SHGFI_SHELLICONSIZE     = 0x000000004,     // get shell size icon
        SHGFI_PIDL              = 0x000000008,     // pszPath is a pidl
        SHGFI_USEFILEATTRIBUTES = 0x000000010,     // use passed dwFileAttribute
        SHGFI_ADDOVERLAYS       = 0x000000020,     // apply the appropriate overlays
        SHGFI_OVERLAYINDEX      = 0x000000040;     // Get the index of the overlay