System.Windows.Forms.ToolStripMenuItem strange behaviour ?

Hi , I have 2 methods that one will invoke other. The one load data and created ToolStripMenuItem, then pass to second method. Inside 2nd method the menu will bind into treenode. The strange is all menus from outside context of 2nd method block will not displayed ?

void LoadData()
{
    // .....
    ToolStripMenuItem item = new ToolStripMenuItem("Menu 1");
    item.Click += .....;
    BindData(...., new ToolStripMenuItem[] { item }, .... ); 
}

void BindData(....., ToolStripMenuItem[] mis, .... )
{
    // ....
    TreeNode n = .....;
    ContextMenuStrip cms = new ContextMenuStrip();
    cms.Items.AddRange(mis); // menu item from parameter won't show up
    
    // but menu item created inside block show up
    ToolStripMenuItem mi = new ToolStripMenuItem("Inside");
    cms.Items.Add(mi);    // show up

    n.ContextMenuStrip = cms; // bind menu-strip
}

It's hard to be advanced programmer