How to convert entity classes and XML in C#

using System;
using ;
using ;
/// <summary>
/// XML serialization public processing class/// </summary>
public static class XmlSerializeHelper
{
    /// <summary>
    /// Convert entity objects to XML    /// </summary>
    /// <typeparam name="T">Entity type</typeparam>    /// <param name="obj">Entity Object</param>    public static string XmlSerialize&lt;T&gt;(T obj)
    {
        try
        {
            using (StringWriter sw = new StringWriter())
            {
                Type t = ();
                XmlSerializer serializer = new XmlSerializer(());
                (sw, obj);
                ();
                return ();
            }
        }
        catch (Exception ex)
        {
            throw new Exception("Convert entity objects to XML exception", ex);
        }
    }
    /// &lt;summary&gt;
    /// Convert XML to entity object    /// &lt;/summary&gt;
    /// <typeparam name="T">Entity type</typeparam>    /// &lt;param name="strXML"&gt;XML&lt;/param&gt;
    public static T DESerializer&lt;T&gt;(string strXML) where T : class
    {
        try
        {
            using (StringReader sr = new StringReader(strXML))
            {
                XmlSerializer serializer = new XmlSerializer(typeof(T));
                return (sr) as T;
            }
        }
        catch (Exception ex)
        {
            throw new Exception("Convert XML to entity object exception", ex);
        }
    }
}

/// <summary>
/// User information category/// </summary>
public class UserInfo
{
    /// <summary>
    /// serial number    /// </summary>
    public int ID { get; set; }
    /// <summary>
    /// Name    /// </summary>
    public string Name { get; set; }
    /// <summary>
    /// Creation time    /// </summary>
    public DateTime? CreateTime { get; set; }
}

/// <summary>
/// Convert List and XML to each other/// </summary>
public static void ListToXmlTest()
{
    //Get user list    List<UserInfo> userList = GetUserList();
    //Convert entity objects to XML    string xmlResult = (userList);
    //Convert XML to entity object    List<UserInfo> deResult = <List<UserInfo>>(xmlResult);
}
/// <summary>
/// Get a list of user information/// </summary>
public static List<UserInfo> GetUserList()
{
    List<UserInfo> userList = new List<UserInfo>();
    (new UserInfo() { ID = 1, Name = "Zhang San", CreateTime =  });
    (new UserInfo() { ID = 2, Name = "Li Si", CreateTime =  });
    (new UserInfo() { ID = 2, Name = "Wang Wu" });
    return userList;
}

<?xml version="1.0" encoding="utf-16"?>
<ArrayOfUserInfo xmlns:xsi="http:///2001/XMLSchema-instance" xmlns:xsd="http:///2001/XMLSchema">
  <UserInfo>
    <ID>1</ID>
    <Name>Zhang San</Name>
    <CreateTime>2018-10-04T15:59:53.7761027+08:00</CreateTime>
  </UserInfo>
  <UserInfo>
    <ID>2</ID>
    <Name>Li Si</Name>
    <CreateTime>2018-10-04T15:59:54.9571044+08:00</CreateTime>
  </UserInfo>
  <UserInfo>
    <ID>2</ID>
    <Name>Wang Wu</Name>
    <CreateTime xsi:nil="true" />
  </UserInfo>
</ArrayOfUserInfo>

/// <summary>
/// Convert DataTable and XML to each other/// </summary>
public static void DataTableToXmlTest()
{
    //Create DataTable object    DataTable dt = CreateDataTable();
    //Convert DataTable to XML    string xmlResult = (dt);
    //Convert XML to DataTable    DataTable deResult = <DataTable>(xmlResult);
}
/// <summary>
/// Create DataTable object/// </summary>
public static DataTable CreateDataTable()
{
    //Create DataTable    DataTable dt = new DataTable("NewDt");
    //Create a self-growing ID column    DataColumn dc = ("ID", ("System.Int32"));
    (new DataColumn("Name", ("")));
    (new DataColumn("CreateTime", ("")));
    //Create data    DataRow dr = ();
    dr["ID"] = 1;
    dr["Name"] = "Zhang San";
    dr["CreateTime"] = ;
    (dr);
    dr = ();
    dr["ID"] = 2;
    dr["Name"] = "Li Si";
    dr["CreateTime"] = ;
    (dr);
    dr = ();
    dr["ID"] = 3;
    dr["Name"] = "Wang Wu";
    dr["CreateTime"] = ;
    (dr);
    return dt;
}

<?xml version="1.0" encoding="utf-16"?>
<DataTable>
  <xs:schema  xmlns="" xmlns:xs="http:///2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
    <xs:element name="NewDataSet" msdata:IsDataSet="true" msdata:MainDataTable="NewDt" msdata:UseCurrentLocale="true">
      <xs:complexType>
        <xs:choice minOccurs="0" maxOccurs="unbounded">
          <xs:element name="NewDt">
            <xs:complexType>
              <xs:sequence>
                <xs:element name="ID" type="xs:int" minOccurs="0" />
                <xs:element name="Name" type="xs:string" minOccurs="0" />
                <xs:element name="CreateTime" type="xs:dateTime" minOccurs="0" />
              </xs:sequence>
            </xs:complexType>
          </xs:element>
        </xs:choice>
      </xs:complexType>
    </xs:element>
  </xs:schema>
  <diffgr:diffgram xmlns:msdata="urn:schemas-microsoft-com:xml-msdata" xmlns:diffgr="urn:schemas-microsoft-com:xml-diffgram-v1">
    <DocumentElement>
      <NewDt diffgr: msdata:rowOrder="0" diffgr:hasChanges="inserted">
        <ID>1</ID>
        <Name>Zhang San</Name>
        <CreateTime>2018-10-04T16:06:10.8004082+08:00</CreateTime>
      </NewDt>
      <NewDt diffgr: msdata:rowOrder="1" diffgr:hasChanges="inserted">
        <ID>2</ID>
        <Name>Li Si</Name>
        <CreateTime>2018-10-04T16:06:10.8004082+08:00</CreateTime>
      </NewDt>
      <NewDt diffgr: msdata:rowOrder="2" diffgr:hasChanges="inserted">
        <ID>3</ID>
        <Name>Wang Wu</Name>
        <CreateTime>2018-10-04T16:06:10.8004082+08:00</CreateTime>
      </NewDt>
    </DocumentElement>
  </diffgr:diffgram>
</DataTable>

[XmlRootAttribute("MyCity", Namespace="", IsNullable=false)]     // When this class is an Xml root node, use this as the root node name.  public class City[XmlAttribute("AreaName")]    // It is represented as an Xml node attribute.  <... AreaName="..."/>public string Name[XmlElementAttribute("AreaId", IsNullable = false)]    // It is represented as an Xml node.  <AreaId>...</AreaId>public string Id[XmlArrayAttribute("Areas")]    // It is represented as an Xml hierarchy, with the root of Areas, and each node element of the collection it belongs to is the class name.  <Areas><Area ... /><Area ... /></Areas>public Area[] Areas[XmlElementAttribute("Area", IsNullable = false)]    // represents an Xml node with a horizontal structure.  <Area ... /><Area ... />...public Area[] Areas[XmlIgnoreAttribute]    // Ignore the serialization of this element。

using ;
using ;
/// <summary>
/// Class information category/// </summary>
[XmlRootAttribute("MyClassInfo", Namespace = "ABC_123", IsNullable = false)] 
public class ClassInfo
{
    /// <summary>
    /// Class ID    /// </summary>
    [XmlAttribute("MyClassID")]
    public int ClassID { get; set; }
    /// <summary>
    /// Class name    /// </summary>
    [XmlElementAttribute("MyClassName", IsNullable = false)] 
    public string ClassName { get; set; }
    /// <summary>
    /// The squad leader    /// </summary>
    [XmlElementAttribute("MyTeacher", IsNullable = false)] 
    public string Teacher { get; set; }
    /// <summary>
    /// Student List    /// </summary>
    [XmlArrayAttribute("MyStudents")]  
    public List<Student> StudentList { get; set; }
}

using ;
/// <summary>
/// Student Information/// </summary>
[XmlRootAttribute("MyStudent", IsNullable = false)] 
public class Student
{
    /// <summary>
    /// Student ID    /// </summary>
    [XmlAttribute("MyStuID")]
    public int StuID { get; set; }
    /// <summary>
    /// Student name    /// </summary>
    [XmlElementAttribute("MyStuName", IsNullable = false)] 
    public string StuName { get; set; }
    /// <summary>
    /// gender    /// </summary>
    [XmlElementAttribute("MySex", IsNullable = false)] 
    public string Sex { get; set; }
    /// <summary>
    /// Mail    /// </summary>
    [XmlIgnoreAttribute] 
    public string Email { get; set; }
}

/// <summary>
/// Convert class information to XML/// </summary>
public static void ClassInfoToXml()
{
    //Get class information    ClassInfo classInfo = GetClassInfo();
    //Convert class information to XML    string classXml = (classInfo);
}
/// <summary>
/// Get class information/// </summary>
public static ClassInfo GetClassInfo()
{
    //Create class information    ClassInfo classInfo = new ClassInfo();
     = 1;
     = "Class 1st Grade (5)";
     = "Teacher Li";
    //Create a student list    List<Student> studentList = new List<Student>();
    (new Student() { StuID = 1, StuName = "Zhang San", Sex = "male", Email = "zhangsan@" });
    (new Student() { StuID = 2, StuName = "Li Si", Sex = "female", Email = "lisi@" });
    (new Student() { StuID = 3, StuName = "Wang Wu", Sex = "male", Email = "wangwu@" });
     = studentList;
    return classInfo;
}

<?xml version="1.0" encoding="utf-16"?>
<MyClassInfo xmlns:xsi="http:///2001/XMLSchema-instance" xmlns:xsd="http:///2001/XMLSchema" MyClassID="1" xmlns="ABC_123">
  <MyClassName>First year of high school（5）class</MyClassName>
  <MyTeacher>Teacher Li</MyTeacher>
  <MyStudents>
    <Student MyStuID="1">
      <MyStuName>Zhang San</MyStuName>
      <MySex>male</MySex>
    </Student>
    <Student MyStuID="2">
      <MyStuName>Li Si</MyStuName>
      <MySex>female</MySex>
    </Student>
    <Student MyStuID="3">
      <MyStuName>Wang Wu</MyStuName>
      <MySex>male</MySex>
    </Student>
  </MyStudents>
</MyClassInfo>