C# 检查DropDownList中选择的值，并对照XML值进行检查

基本上，我要做的是检查dropDownList1中选择的值是否在XML文档中，如果是，则打印出它的fat内容。否则我将返回字符串“抱歉，我们找不到您的食物！”。就目前而言，我只得到了另一种情况。任何帮助都会很棒

我的代码如下：

 XmlDocument xDoc = new XmlDocument();
        xDoc.Load("the xml address");

        // go through each food name (this works)
        foreach (XmlNode name in xDoc.SelectNodes("Web_Service/Food/Name")) 

        {
           //grab the string
           string foodName = name.InnerText;

           // what I'm tring to here is loop through the items in the dropdown list
           // and check it against foodName
           foreach (ListItem li in DropDownList1.Items)
           {
               if (li.Value == foodName)
               {
                   // print the value fat value of that particular foodName
                  // address is ("Web_Service/Food/Fat")
               }
               else
               {
                   TextBox2.Text = "sorry we could not find your food!";
               }
           }

        }

---

希望我解释得足够好，谢谢各位。

知道dropdownlist的选定值的属性是

SelectedValue

类似：

DropDownList1.SelectedValue  == foodName

我不认为需要第二个循环，因为它甚至不验证是否选中了该项

或者，您可以使用LINQ在XML中获取食物项目列表，具体操作如下：

XDocument doc=XDocument.Load(Server.MapPath("the xml address"));    

var items = (from item in doc.Root.Elements("Web_Service/Food") 
select new {     
    name=c.Element("Name"),
};  

然后，您可以从不同的数组函数中获益，如：

Array.Exists(items, DropDownList1.SelectedValue)

或者在LINQ查询中使用

where

和

let

关键字尽可能地使用它进行筛选：

var items = (from item in doc.Root.Elements("Web_Service/Food") 
let name = c.Element("Name")
where DropDownList1.SelectedValue == name
select new {     
    name=name,
};  

---

将foreach循环替换为以下内容：

string nodeSelect = String.Format("Web_Service/Food/Name[@Value='{0}']",foodName);

XmlNodeList nodes = xDoc.SelectNodes(nodeSelect);

if (nodes.Count == 0)
{

TextBox2.Text = "sorry we could not find your food!";

}

else

{

//print the value fat value of that particular foodName
// address is ("Web_Service/Food/Fat

}

---

您可以使用XPath表达式获取子节点等于所选食物的

节点，然后获取子节点。多功能XPath表达式，因此无需手动循环每个

节点即可完成此操作。例如：

string foodName = DropDownList1.SelectedValue;
string xpath = String.Format("Web_Service/Food[Name='{0}']/Fat", foodName);
XmlNode fatNode = xDoc.SelectSingleNode(xpath);
if(fatNode != null)
{
    TextBox2.Text = fatNode.InnerText;
}
else
{
    TextBox2.Text = "sorry we could not find your food!";
}