C#

+"\\"

foreach (ToolStripMenuItem item in ((ToolStripDropDownItem)sender).Owner.Items)
{
       if (item == sender)
           item.Checked = true;
       else
           item.Checked = false;
}   

Unable to cast object of type 'System.Windows.Forms.ToolStripSeparator' to type 'System.Windows.Forms.ToolStripMenuItem'.

foreach (ToolStripMenuItem item in ((ToolStripSeparator)sender).Owner.Items)
   {
   }

foreach (ToolStripItem item in ((ToolStripDropDownItem)sender).Owner.Items)
{
    if (item.GetType() == typeof(ToolStripMenuItem))
    {
        if (item == sender)
            ((ToolStripMenuItem)item).Checked = true;
        else
            ((ToolStripMenuItem)item).Checked = false;
    }
}

An unhandled exception of type 'System.StackOverflowException' occurred in System.Windows.Forms.dll

// accessing the menu items directly


myToolstripMenuItem1.Checked = true;
myToolstripMenuItem2.Checked = false;
myToolstripMenuItem3.Checked = false;

// accessing the ContextMenuStrip directly

foreach (ToolStripMenuItem item in myContextMenuStrip.Items)
{

.......

}

// set all checked states to false
strip1.Checked = false;
strip2.Checked = false;
strip3.Checked = false;
strip4.Checked = false;
strip5.Checked = false;

// set the senders checked state
((ToolStripMenuItem)sender).Checked = true;

is

if(item is ToolStripMenuItem)