xpath starts-with函数出错！大家帮忙
我的xpath是这样写的：

xpath := '/Documents/Document[starts-with(@Index, ' 'D ' ')] ';

然后调用：SelectSingleNode(xpath)

运行时出错：Unknow Method
请帮忙啊～～

给出代码片断供参考：
-----------------------------
// Delphi
var
xpath: string;
node: IXMLDOMNode;
begin
xpath := '/Documents/Document[starts-with(@Index, ' 'D ' ')] ';
node := doc.SelectSingleNode(xpath);
end;

----------------------------
// c#
string xpath = "/Documents/Document[starts-with(@Index, ' 'D ' ')] ";
XmlNode node = doc.SelectSingleNode(xpath);



[解决办法]
string xpath = "/Documents/Document[starts-with(@Index, 'D ')] ";
O.o