如何使用Linq中的XML屬性

Question

我想選擇XML元素如下。請知道數據和派對是班級。誰能幫如何實現以下內容：

選擇新的數據
{
Party.Name = xElem.Element（ 「名稱」）值，
Party.PostBox = xElem.Element（ 「郵筒」。 ）.Value，
}

使用當前代碼，我無法訪問Party的屬性。

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：以下是示例代碼。我只在運行時得到「對象引用未設置爲對象的實例」錯誤。

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; } 
    } 
} 

---

@喬恩飛碟雙向：下面是示例代碼。我只在運行時得到「對象引用未設置爲對象的實例」錯誤。

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 
    } 
} 

注意，這無關與XML並沒有什麼真正做LINQ - 它只是使用對象初始化功能。你可能想使用從XElement到string而不是使用Value的顯式轉換考慮

一兩件事 - 這樣，如果一個元素缺失，你會得到一個空引用，而不是例外。這取決於你想要什麼樣的行爲，但作爲一個選項值得了解。