private void ExpandOrCollapse(bool collapse)
{
CheckControlEnabled();
// Check if item can be expanded or collapsed.
bool isCollapsed = IsCollapsed();
if ((!collapse && !isCollapsed) || (collapse && isCollapsed))
{
throw new InvalidOperationException(SR.Get(SRID.OperationCannotBePerformed));
}
NativeMethods.LVGROUP group = new NativeMethods.LVGROUP();
group.Init(Marshal.SizeOf(typeof(NativeMethods.LVGROUP)));
// Note: If we set group.mask to LVGF_GROUPID | LVGF_STATE,
// SetGroupInfo() will fail. Setting LVGF_STATE alone works, however.
group.mask = NativeMethods.LVGF_STATE;
group.iGroupID = _groupID;
group.stateMask = NativeMethods.LVGS_COLLAPSED;
group.state = collapse ? NativeMethods.LVGS_COLLAPSED : 0;
if (!XSendMessage.SetGroupInfo(_hwnd, group))
{
throw new InvalidOperationException(SR.Get(SRID.OperationCannotBePerformed));
}
}
internal static bool IsCollapsed(IntPtr hwnd, int groupID)
{
bool isCollapsed = false;
NativeMethods.LVGROUP group = new NativeMethods.LVGROUP();
group.Init(Marshal.SizeOf(typeof(NativeMethods.LVGROUP)));
group.iGroupID = groupID;
group.mask = NativeMethods.LVGF_STATE;
group.stateMask = NativeMethods.LVGS_COLLAPSED;
// Note: return code of GetGroupInfo() is not reliable.
XSendMessage.GetGroupInfo(hwnd, ref group); // ignore return code.
isCollapsed = (group.state & NativeMethods.LVGS_COLLAPSED) != 0;
return isCollapsed;
}