Web Forms :: String Builder - Syntax Error

i am using stringbuilder but i have hit a problem. the line below

sb.AppendLine("ctl00_ContentPlaceHolder1_rptNav_ctl00_AssetsTreeControl_1_pnlAssetsContext");

i need this to be passed as a string value ie

ctl00_ContentPlaceHolder1_rptNav_ctl00_AssetsTreeControl_1_pnlAssetsContext
'ctl00_ContentPlaceHolder1_rptNav_ctl00_AssetsTreeControl_1_pnlAssetsContext'

the problem is if i do this i get a js error of
Error: syntax error
Source Code:
return ShowContextMenu(event,
StringBuilder sb = new StringBuilder();
sb.AppendLine("<b Id='");
sb.AppendLine(assets_item.Id.ToString());
sb.AppendLine("' oncontextmenu='return ShowContextMenu(event, ");
sb.AppendLine("ctl00_ContentPlaceHolder1_rptNav_ctl00_AssetsTreeControl_1_pnlAssetsContext");
sb.AppendLine(")'>");
sb.AppendLine(assets_item.Title);
sb.AppendLine("</b>");