C＃写入xml文件元素访问问题

Question

我试图从1个numericUpDown和3个文本框中写入数据到一个xml文件。但是，我无法跨方法访问XDocument文件的元素。

下面是我的代码和我所有的评论。你能帮助一个完整的noob到XML和网站？所有改进建议欢迎！

using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 
using System.Windows.Forms; 
using System.Xml; 
using System.IO; 
using System.Xml.Linq; 
namespace AA 
{ 
public partial class Form1 : Form 
{ 
    //Will be used to check if the file exists in the save directory 
    byte ifexists = 0; 

    //method for file creation 
    public void fileCreate() 
    { 
     XDocument XDoc = new XDocument(
      new XDeclaration("1.0", "UTF-16", null), 
       new XElement("Group", 
        new XElement("A"), 
        new XElement("B"), 
        new XElement("C"), 
        new XElement("D") 
       )); 
    } 
//method for file save (want to save 4 values from 1 numericUpDown and 3 textboxes, when I solve file creation problems I want to use numericUpDown value as an ID and load relevant info from the xml file 
    public void fileSave() 
    { 
    //i tried to use serverpath which seems to be better but i couldn't get it to work so I used Application.StartupPath.... 
    XDocument XDoc = XDocument.Load(Application.StartupPath + "\\..\\File.xml"); 
    Group.Add(new XElement("A", nUDforA.Value)); 
    Group.Add(new XElement("B", tBforB.Text)); 
    Group.Add(new XElement("C", tBforC.Text)); 
    Group.Add(new XElement("D", tBforD.Text)); 
    XDoc.Add(Group); 
    XDoc.Save(Application.StartupPath + "\\..\\File.xml");} 

    public Form1() 
    { 
     InitializeComponent(); 
    } 
    //this label is used to write "Saved!"after clicking the "Write" button and become invisible again after 1 second timertick 
    private void Form1_Load(object sender, EventArgs e) 
    { 
     //this label is used to write "Saved!"after clicking the "Write" button and become invisible again after 1 second timertick 
     lblSituation.Visible = false; 
    } 

    private void btnWrite_Click(object sender, EventArgs e) 
    { 
    //first check if the file exists 
     if (File.Exists(Application.StartupPath +"\\..\\File.xml")) 

{ 
    ifexists = 1; 
    fileSave(); 
} 
     if (ifexists==0) 
     { 
      fileCreate(); 
      fileSave(); 
     } 
     //saying the user that the file is saved 
     lblSituation.Visible = true; 
     lblSituation.Text = "Saved!"; 
     timer1.Enabled = true; 
     } 

    private void timer1_Tick(object sender, EventArgs e) 
    { 
     lblSituation.Visible = false; 
     timer1.Enabled = false; 

    } 
} 
} 

Answer 1

你应该使用XDoc.Root.Add当你添加新的elements.What是Group？这是你的第一要素，但是，你不能用它的名字一样，访问它：

Group.Add(new XElement("A", nUDforA.Value)); 

首先用A，B，C，d元素的新组元素：

var groupElement = new XElement("Group", 
         new XElement("A", nUDforA.Value), 
         new XElement("B", tBforB.Text), 
         new XElement("C", tBforC.Text), 
         new XElement("D", tBforD.Text)); 

然后加入它给你的XDocument：

XDoc.Root.Add(groupElement); 

如果要更新第一组元素的这些值，那么你可以做到以下几点：

var groupElement = XDoc.Descendants("Group").FirstOrDefault(); 
if(groupElement != null) 
{ 
    var newElement = new XElement("Group", 
         new XElement("A", nUDforA.Value), 
         new XElement("B", tBforB.Text), 
         new XElement("C", tBforC.Text), 
         new XElement("D", tBforD.Text)); 
    groupElement.ReplaceAll(newElement); 
    // save the document 
} 

注意：您还应该保存您的XML Document在您的fileCreate方法，如评论中所述。