Question

我想选择如下的XML元素。请知道数据和派对是课程。有人可以帮助如何实现以下目标：

选择新数据
        {
            Party.Name = xElem.Element（“Name”）。值，
            Party.PostBox = xElem.Element（“PostBox”）。值，
        }

使用当前代码，我无法访问Party的属性。

static void Main(string[] args)
{
     XDocument doc = XDocument.Load(@"c:\test.xml");
     var q = from xElem in doc.Descendants("Party")
         where (int)xElem.Attribute("ID") == 1
         select new Data
         {

         };
}

public class Data
{
    public Party Party { get; set; }
    public Data()
    {
        this.Party = new Party();
    }
}

public class Party
{
    string name;
    string postbox;

    public string Name
    {
        get { return name; }
        set { this.name = value; }
    }

    public string PostBox
    {
        get { return postbox; }
        set { this.postbox = value; }
    }
}

@Jon Skeet：以下是示例代码。我只在运行时获得“对象引用未设置为对象的实例”错误。

static void Main(string[] args)
{
    XDocument doc = XDocument.Load(@"c:\test\data.xml");
    var props = from xElem in doc.Descendants("Party")
        where (int)xElem.Attribute("ID") == 1
        select new Data
        {
              Party =
              {
                  Name = xElem.Element("Name").Value.ToString(),
                  PostBox = xElem.Element("PostBox").Value.ToString(),
                  Tax =
                  {
                     CompanyID = xElem.Element("Tax").Element("CompanyID").Value.ToString()
                  }
              }
        }
}


public class Data
{
    public Party Party { get; set; }
    public Data()
    {
        this.Party= new Party();
    }
}

public class Party
{
    string name;
    string postbox;

    public Tax Tax { get; set; }

    public string Name
    {
        get { return name; }
        set { this.name = value; }
    }

    public string PostBox
    {
        get { return postbox; }
        set { this.postbox = value; }
    }
}

public class Tax
{
    string companyid;

    public string CompanyID
    {
        get { return companyid; }
        set { this.companyid = value; }
    }
}

@Jon Skeet：以下是示例代码。我只在运行时获得“对象引用未设置为对象的实例”错误。

static void Main(string[] args)
{
    XDocument doc = XDocument.Load(@"c:\test\data.xml");
    var props = from xElem in doc.Descendants("Party")
        where (int)xElem.Attribute("ID") == 1
        select new Data
        {
              Party =
              {
                  Name = xElem.Element("Name").Value.ToString(),
                  PostBox = xElem.Element("PostBox").Value.ToString(),
                  Tax =
                  {
                     CompanyID = xElem.Element("Tax").Element("CompanyID").Value.ToString()
                  }
              }
        }
}


public class Data
{
    public Party Party { get; set; }
    public Data()
    {
        this.Party= new Party();
    }
}

public class Party
{
    string name;
    string postbox;

    public Tax Tax { get; set; }

    public string Name
    {
        get { return name; }
        set { this.name = value; }
    }

    public string PostBox
    {
        get { return postbox; }
        set { this.postbox = value; }
    }
}

public class Tax
{
    string companyid;

    public string CompanyID
    {
        get { return companyid; }
        set { this.companyid = value; }
    }
}

Answer 1

你想：

// Modifies the existing Party created in the Data constructor
select new Data 
{ 
    Party =
    {
        Name = xElem.Element("Name").Value, 
        PostBox = xElem.Element("PostBox").Value
    }
}

或：

// Creates a new Party and then calls the Data.Party setter
select new Data 
{ 
    Party = new Party
    {
        Name = xElem.Element("Name").Value, 
        PostBox = xElem.Element("PostBox").Value
    }
}

请注意，这与XML无关，与LINQ没有任何关系 - 它只是使用对象初始化器功能。

您可能想要考虑的一件事是使用从XElement到string的显式转换，而不是使用Value - 这样如果缺少某个元素，则会获得空引用一个例外。这取决于你想要的行为，但值得了解作为一种选择。

如何在Linq to XML中使用属性

1 个答案: