使用 linq 使用多个条件搜索和更新 XML

Posted 2023-04-12

【中文标题】使用 linq 使用多个条件搜索和更新 XML

【英文标题】：Search and Update XML using multiple condition using linq

【发布时间】：2020-12-06 02:58:51

【问题描述】：

<Students>
  <Student Name="John">
    <Subject SubId="123" Content="History minor subject" Enrolled="true" Percentage="0"/>
    <Subject SubId="146" Content="Math major Subject"  Enrolled="true" Percentage="0"/>
  </Student>
  <Student Name="Jim">
    <Subject SubId="564" Content="physics medium subject" Enrolled="true" Percentage="0"/>
    <Subject SubId="324" Content="Chem small subject" Enrolled="true" Percentage="0"/>
  </Student>
<Students>

问题 1 - 我想搜索人名内容 John 和内容是否具有“专业”-> 返回 Xelememt ，我正在尝试使用以下查询，但它对我不起作用。

字符串 studentToSearch = "John" 和字符串 contentToSearch = "major"

    IEnumerable<XElement> student = from st in rootElement.Descendants("Students").Elements("Student")
                                             where st.Attribute("Name").Value.ToString() == studentToSearch && st.Element("Subject").Attribute("Content").Value.ToString().Contains(contentToSearch)
                                             select st;
                                                 
                                                 

问题 2 - 我想搜索人名内容 John 和内容是否具有“主要”，如果找到它的百分比为“0”--> 然后将其更新为“80”百分比。尝试以下查询

  rootElement.Elements("Students")
                            .Where(x=> x.Element("Student").Value == studentToSearch)
                            .Where(a => a.Element("Subject").Attributes("Content").ToString().Contains(contentToSearch) && a.Element("Subject").Attribute("Percentage").Value == "0").FirstOrDefault()
                            .SetAttributeValue("Percentage", 80);  

任何建议都会有所帮助？

【参考方案1】：

为什么不直接反序列化 xml？您需要使用 SelectMany。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Serialization;

namespace ConsoleApplication1

    class Program
    
        const string FILENAME = @"c:\temp\test.xml";
        static void Main(string[] args)
        
            XmlReader reader = XmlReader.Create(FILENAME);
            XmlSerializer serializer = new XmlSerializer(typeof(Students));
            Students students = (Students)serializer.Deserialize(reader);

            var johnMajor = students.Student.SelectMany(x => x.Subject.Where(y => y.Content.Contains("major")).Select(z => new  name = x.Name, Subject = z )).FirstOrDefault();
            if (johnMajor.Subject.Percentage == 0) johnMajor.Subject.Percentage = 80;
        
    
    public class Students
    
        [XmlElement()]
        public List<Student> Student  get; set; 
    
    public class Student
    
        [XmlAttribute()]
        public string Name  get; set; 
        [XmlElement]
        public List<Subject> Subject  get; set; 
    
    public class Subject
    
        [XmlAttribute()]
        public int SubId  get; set; 
        [XmlAttribute()]
        public string Content  get; set; 
        [XmlAttribute()]
        public Boolean Enrolled  get; set; 
        [XmlAttribute()]
        public int Percentage  get; set;