c# - xml 错误 : Object reference not set to an instance of an object after SelectSingleNode

Question

这是我的代码:

XmlDocument doc = new XmlDocument();
foreach (string c in colorList)
{
     doc.Load(@"http://whoisxmlapi.com/whoisserver/WhoisService?domainName=" + c + @"&username=user&password=pass");
     textBox1.Text += doc.SelectSingleNode("WhoisRecord/registrant/email").InnerText + ",";
}

第二行代码 (textbox1...) 产生了这个错误 我做错了什么？

Answer 1

如何拆分行以查看异常发生的位置？

// if node is null the problem is with SelectSingleNode 
XmlNode node = doc.SelectSingleNode("WhoisRecord/registrant/email");

// if text is null the problem is with the node 
string text = node.InnerText;

// if textBox1 is null the problem is with textBox1
textBox1.Text += text + ",";