Question

我正在努力使用LINQ来 ~~SQL~~ XML。我正在关注示例并取得一些好成绩。但是我遇到了一个问题，希望有人可以帮助我。

<root>
<MyItem  Host="00155DFF045C" LastName="HOUSTON" FirstName="WHITNEY" >
    <TimeStamp ComputerTime="02/07/2011 - 21:41:53.715">
        <Group Name="Group1">
            <Variable ID="1001" Value="Happy" >
            </Variable>
        </Group>
        <Group Name="Group2">
            <Variable ID="2000" Value="Monday" >
            </Variable>
            <Variable ID="2001" Value="Tuesday" >
            </Variable>
        </Group>
        <Group Name="Group3">
            <Variable ID="3000" Value="January" >
            </Variable>
            <Variable ID="3001" Value="February" >
            </Variable>
        </Group>
        <Group Name="Groupe4">
            <Variable ID="4001" Value="108.000000" >
            </Variable>
            <Variable ID="4002" Value="800" >
            </Variable>
        </Group>
        <Group Name="CustomGroup">
            <Variable ID="1001000" Value="1.000000" >
            </Variable>
        </Group>
    </TimeStamp>
</MyItem>
<MyItem>
...
...
</MyItem>
</root>

由于教程，我正确地获得了{Host="00155DFF045C" LastName="HOUSTON" FirstName="WHITNEY}之类的信息。

但我需要获得更多信息。如何使用属于Value的{{1}}检索ID="4001"变量元素？

我目前的代码是：

Groupe4

使用此代码，我可以正确获取XElement xmlTweets = XElement.Parse(e.Result); var toto = from tweet in xmlTweets.Descendants("MyItem").Take(10) orderby tweet.Element("TimeStamp").Attribute("ComputerTime").Value descending select new History { DisplayName = tweet.Attribute("PatientFirstName").Value + " " + tweet.Attribute("PatientLastName").Value };的值。我想得到变量DisplayName的值，即值4001。

Answer 1

如果您对特定元素有引用，则可以使用Element()或Attribute()方法从其任何嵌套元素中获取值。您可以使用Elements()或Attributes()获取这些列表，以对它们执行LINQ查询。假设我们有对root元素的引用，您可以获得以下信息：

XElement root = ...;
XElement myItem = root.Element("MyItem");               // get the first "MyItem" element
string Host = myItem.Attribute("Host").Value;           // get value of "Host" attribute
string LastName = myItem.Attribute("LastName").Value;   // get value of "LastName" attribute
string FirstName = myItem.Attribute("FirstName").Value; // get value of "FirstName" attribute

// find "Groupe4"
XElement Groupe4 = (from g in myItem.Element("TimeStamp")
                                    .Elements("Group")
                    where g.Attribute("Name").Value == "Groupe4"
                    select g)   // only one element should be found
                   .Single();   // assign that element to variable Groupe4

// Get Value of Variable with ID = 4001
double Value4001 = (from v in Groupe4.Elements("Variable") // of all Variable elements
                    where (int)v.Attribute("ID") == 4001   // choose elements where ID = 4001
                    select (double)v.Attribute("Value"))   // select the Value
                   .Single();                              // assign that value to variable Value 4001

因此，要将其应用于您的查询，您可以执行以下操作：

XElement xmlTweets = XElement.Parse(e.Result);
var id = 4001;   // the ID to find
var toto = from tweet in xmlTweets.Descendants("MyItem")
                                  .Take(10)
           orderby (DateTime)tweet.Element("TimeStamp")
                                  .Attribute("ComputerTime") descending
           select new History {
               DisplayName = String.Format("{0} {1}",
                   tweet.Attribute("PatientFirstName").Value,
                   tweet.Attribute("PatientLastName").Value),

               // find the Variable with matching ID and get its Value as a double
               Value = (from v in tweet.Descendants("Variable")
                        where (int)v.Attribute("ID") == id
                        select (double)v.Attribute("Value"))
                       .Single()
           };

Answer 2

一旦有XElement变量名为myItemElement，

     myItemElement
            .Element("TimeStamp")
            .Elements("Group")
            .FirstOrDefault(x => x.Attribute("Name") != null && x.Attribute("Name").Value == "Groupe4")
            .Elements("Variable")
            .FirstOrDefault(x => x.Attribute("ID") != null && x.Attribute("ID").Value == "4001")
            .Attribute("Value").Value;

如何从其他嵌套元素中获取信息？

2 个答案: