XML 序列化的範例
XML 序列化的形式不只一種，從簡單到複雜都有。 例如，您可序列化僅包含公用欄位及屬性的類別，如 XML 序列化簡介中所示。 下列程式碼範例說明各種不同的進階案例，包括如何使用 XML 序列化以產生符合特定 XML 結構描述 (XSD) 文件的 XML 資料流。
序列化資料集
除了序列化公用類別的執行個體之外，您也可以序列化 DataSet 的執行個體，如下列程式碼範例所示：
Private Sub SerializeDataSet(filename As String)
Dim ser As XmlSerializer = new XmlSerializer(GetType(DataSet))
' Creates a DataSet; adds a table, column, and ten rows.
Dim ds As DataSet = new DataSet("myDataSet")
Dim t As DataTable = new DataTable("table1")
Dim c As DataColumn = new DataColumn("thing")
t.Columns.Add(c)
ds.Tables.Add(t)
Dim r As DataRow
Dim i As Integer
for i = 0 to 10
r = t.NewRow()
r(0) = "Thing " & i
t.Rows.Add(r)
Next
Dim writer As TextWriter = new StreamWriter(filename)
ser.Serialize(writer, ds)
writer.Close()
End Sub
private void SerializeDataSet(string filename)
{
XmlSerializer ser = new XmlSerializer(typeof(DataSet));
// Creates a DataSet; adds a table, column, and ten rows.
DataSet ds = new DataSet("myDataSet");
DataTable t = new DataTable("table1");
DataColumn c = new DataColumn("thing");
t.Columns.Add(c);
ds.Tables.Add(t);
DataRow r;
for (int i = 0; i < 10; i++) {
r = t.NewRow();
r[0] = "Thing " + i;
t.Rows.Add(r);
}
TextWriter writer = new StreamWriter(filename);
ser.Serialize(writer, ds);
writer.Close();
}
序列化 XmlElement 與 XmlNode
您也可序列化 XmlElement 或 XmlNode 類別的執行個體，如下列程式碼範例所示：
private Sub SerializeElement(filename As String)
Dim ser As XmlSerializer = new XmlSerializer(GetType(XmlElement))
Dim myElement As XmlElement = _
new XmlDocument().CreateElement("MyElement", "ns")
myElement.InnerText = "Hello World"
Dim writer As TextWriter = new StreamWriter(filename)
ser.Serialize(writer, myElement)
writer.Close()
End Sub
Private Sub SerializeNode(filename As String)
Dim ser As XmlSerializer = _
new XmlSerializer(GetType(XmlNode))
Dim myNode As XmlNode = new XmlDocument(). _
CreateNode(XmlNodeType.Element, "MyNode", "ns")
myNode.InnerText = "Hello Node"
Dim writer As TextWriter = new StreamWriter(filename)
ser.Serialize(writer, myNode)
writer.Close()
End Sub
private void SerializeElement(string filename)
{
XmlSerializer ser = new XmlSerializer(typeof(XmlElement));
XmlElement myElement = new XmlDocument().CreateElement("MyElement", "ns");
myElement.InnerText = "Hello World";
TextWriter writer = new StreamWriter(filename);
ser.Serialize(writer, myElement);
writer.Close();
}
private void SerializeNode(string filename)
{
XmlSerializer ser = new XmlSerializer(typeof(XmlNode));
XmlNode myNode = new XmlDocument().
CreateNode(XmlNodeType.Element, "MyNode", "ns");
myNode.InnerText = "Hello Node";
TextWriter writer = new StreamWriter(filename);
ser.Serialize(writer, myNode);
writer.Close();
}
序列化包含傳回複雜物件欄位的類別
如果屬性或欄位傳回複雜物件 (例如陣列或類別執行個體)，XmlSerializer 會將它轉換為主要 XML 文件中的巢狀項目。 例如，下列程式碼範例中的第一個類別，會傳回第二個類別的執行個體：
Public Class PurchaseOrder
Public MyAddress As Address
End Class
Public Class Address
Public FirstName As String
End Class
public class PurchaseOrder
{
public Address MyAddress;
}
public record Address
{
public string FirstName;
}
序列化的 XML 輸出可能如下所示：
<PurchaseOrder>
<MyAddress>
<FirstName>George</FirstName>
</MyAddress>
</PurchaseOrder>
序列化物件陣列
您也可序列化傳回物件陣列的欄位，如下列程式碼範例所示：
Public Class PurchaseOrder
public ItemsOrders () As Item
End Class
Public Class Item
Public ItemID As String
Public ItemPrice As decimal
End Class
public class PurchaseOrder
{
public Item [] ItemsOrders;
}
public class Item
{
public string ItemID;
public decimal ItemPrice;
}
如果兩個項目已設定順序，則已序列化的類別執行個體可能如下列程式碼所示：
<PurchaseOrder xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<ItemsOrders>
<Item>
<ItemID>aaa111</ItemID>
<ItemPrice>34.22</ItemPrice>
</Item>
<Item>
<ItemID>bbb222</ItemID>
<ItemPrice>2.89</ItemPrice>
</Item>
</ItemsOrders>
</PurchaseOrder>
序列化實作 ICollection 介面的類別
您可以實作 ICollection 介面來建立自己的集合類別，並且使用 XmlSerializer 對這些類別的執行個體序列化。
注意
當類別實作 ICollection 介面時，只會序列化該類別包含的集合。 加入至該類別的任何公用屬性或欄位都不會序列化。 該類別必須包含 Add 方法及 Item 屬性 (C# 索引子) 才能序列化。
Imports System.Collections
Imports System.IO
Imports System.Xml.Serialization
Public Class Test
Shared Sub Main()
Dim t As Test= new Test()
t.SerializeCollection("coll.xml")
End Sub
Private Sub SerializeCollection(filename As String)
Dim Emps As Employees = new Employees()
' Note that only the collection is serialized -- not the
' CollectionName or any other public property of the class.
Emps.CollectionName = "Employees"
Dim John100 As Employee = new Employee("John", "100xxx")
Emps.Add(John100)
Dim x As XmlSerializer = new XmlSerializer(GetType(Employees))
Dim writer As TextWriter = new StreamWriter(filename)
x.Serialize(writer, Emps)
writer.Close()
End Sub
End Class
Public Class Employees
Implements ICollection
Public CollectionName As String
Private empArray As ArrayList = new ArrayList()
Public ReadOnly Default Overloads _
Property Item(index As Integer) As Employee
get
return CType (empArray(index), Employee)
End Get
End Property
Public Sub CopyTo(a As Array, index As Integer) _
Implements ICollection.CopyTo
empArray.CopyTo(a, index)
End Sub
Public ReadOnly Property Count () As integer Implements _
ICollection.Count
get
Count = empArray.Count
End Get
End Property
Public ReadOnly Property SyncRoot ()As Object _
Implements ICollection.SyncRoot
get
return me
End Get
End Property
Public ReadOnly Property IsSynchronized () As Boolean _
Implements ICollection.IsSynchronized
get
return false
End Get
End Property
Public Function GetEnumerator() As IEnumerator _
Implements IEnumerable.GetEnumerator
return empArray.GetEnumerator()
End Function
Public Function Add(newEmployee As Employee) As Integer
empArray.Add(newEmployee)
return empArray.Count
End Function
End Class
Public Class Employee
Public EmpName As String
Public EmpID As String
Public Sub New ()
End Sub
Public Sub New (newName As String , newID As String )
EmpName = newName
EmpID = newID
End Sub
End Class
using System;
using System.Collections;
using System.IO;
using System.Xml.Serialization;
public class Test
{
static void Main()
{
Test t = new Test();
t.SerializeCollection("coll.xml");
}
private void SerializeCollection(string filename)
{
Employees Emps = new Employees();
// Note that only the collection is serialized -- not the
// CollectionName or any other public property of the class.
Emps.CollectionName = "Employees";
Employee John100 = new Employee("John", "100xxx");
Emps.Add(John100);
XmlSerializer x = new XmlSerializer(typeof(Employees));
TextWriter writer = new StreamWriter(filename);
x.Serialize(writer, Emps);
}
}
public class Employees : ICollection
{
public string CollectionName;
private ArrayList empArray = new ArrayList();
public Employee this[int index] => (Employee) empArray[index];
public void CopyTo(Array a, int index)
{
empArray.CopyTo(a, index);
}
public int Count => empArray.Count;
public object SyncRoot => this;
public bool IsSynchronized => false;
public IEnumerator GetEnumerator() => empArray.GetEnumerator();
public void Add(Employee newEmployee)
{
empArray.Add(newEmployee);
}
}
public class Employee
{
public string EmpName;
public string EmpID;
public Employee() {}
public Employee(string empName, string empID)
{
EmpName = empName;
EmpID = empID;
}
}
採購單範例
您可以將下列範例程式碼剪下並貼至文字檔，然後將文字檔重新命名為 .cs 或 .vb 副檔名。 使用 C# 或 Visual Basic 編譯器編譯檔案。 然後使用可執行檔的名稱執行它。
此範例使用簡單的案例，顯示如何使用 Serialize 方法將物件的執行個體建立及序列化為檔案資料流。 XML 資料流會儲存至檔案。 然後使用 Deserialize 方法讀取相同檔案並重新建構為原始物件的複本。
在此範例中，會序列化名為 PurchaseOrder 的類別，然後再將其還原序列化。 也包含名為 Address 的第二類別，因為名為 ShipTo 的公用欄位必須設定為 Address。 同樣地，會包含 OrderedItem 類別，因為 OrderedItem 物件的陣列必須設定為 OrderedItems 欄位。 最後，名為 Test 的類別包含序列化與還原序列化類別的程式碼。
CreatePO 方法會建立 PurchaseOrder、Address 和 OrderedItem 類別物件，並且設定公用欄位的值。 該方法也建構用來序列化及還原序列化 PurchaseOrder 之 XmlSerializer 類別的執行個體。
注意
程式碼把要序列化之類別的型別傳遞給建構函式。 程式碼也建立用來將 XML 資料流寫入 XML 文件的 FileStream。
ReadPo 方法比較簡單。 它只會建立要還原序列化的物件，並讀出它們的值。 如同 CreatePo 方法，您必須先建構 XmlSerializer，將要還原序列化之類別的型別傳遞給建構函式。 同時，需要有 FileStream 讀取 XML 文件。 若要還原序列化物件，以 Deserialize 做為引數呼叫 FileStream 方法。 還原序列化物件必須轉型為型別 PurchaseOrder的物件變數。 然後程式碼會讀取已還原序列化的 PurchaseOrder值。
注意
您可以讀取已建立的 PO.xml 檔案，檢視實際的 XML 輸出。
Imports System.IO
Imports System.Xml
Imports System.Xml.Serialization
Imports Microsoft.VisualBasic
' The XmlRoot attribute allows you to set an alternate name
' (PurchaseOrder) for the XML element and its namespace. By
' default, the XmlSerializer uses the class name. The attribute
' also allows you to set the XML namespace for the element. Lastly,
' the attribute sets the IsNullable property, which specifies whether
' the xsi:null attribute appears if the class instance is set to
' a null reference.
<XmlRoot("PurchaseOrder", _
Namespace := "http://www.cpandl.com", IsNullable := False)> _
Public Class PurchaseOrder
Public ShipTo As Address
Public OrderDate As String
' The XmlArrayAttribute changes the XML element name
' from the default of "OrderedItems" to "Items".
<XmlArray("Items")> _
Public OrderedItems() As OrderedItem
Public SubTotal As Decimal
Public ShipCost As Decimal
Public TotalCost As Decimal
End Class
Public Class Address
' The XmlAttribute attribute instructs the XmlSerializer to serialize the
' Name field as an XML attribute instead of an XML element (XML element is
' the default behavior).
<XmlAttribute()> _
Public Name As String
Public Line1 As String
' Setting the IsNullable property to false instructs the
' XmlSerializer that the XML attribute will not appear if
' the City field is set to a null reference.
<XmlElement(IsNullable := False)> _
Public City As String
Public State As String
Public Zip As String
End Class
Public Class OrderedItem
Public ItemName As String
Public Description As String
Public UnitPrice As Decimal
Public Quantity As Integer
Public LineTotal As Decimal
' Calculate is a custom method that calculates the price per item
' and stores the value in a field.
Public Sub Calculate()
LineTotal = UnitPrice * Quantity
End Sub
End Class
Public Class Test
Public Shared Sub Main()
' Read and write purchase orders.
Dim t As New Test()
t.CreatePO("po.xml")
t.ReadPO("po.xml")
End Sub
Private Sub CreatePO(filename As String)
' Creates an instance of the XmlSerializer class;
' specifies the type of object to serialize.
Dim serializer As New XmlSerializer(GetType(PurchaseOrder))
Dim writer As New StreamWriter(filename)
Dim po As New PurchaseOrder()
' Creates an address to ship and bill to.
Dim billAddress As New Address()
billAddress.Name = "Teresa Atkinson"
billAddress.Line1 = "1 Main St."
billAddress.City = "AnyTown"
billAddress.State = "WA"
billAddress.Zip = "00000"
' Set ShipTo and BillTo to the same addressee.
po.ShipTo = billAddress
po.OrderDate = System.DateTime.Now.ToLongDateString()
' Creates an OrderedItem.
Dim i1 As New OrderedItem()
i1.ItemName = "Widget S"
i1.Description = "Small widget"
i1.UnitPrice = CDec(5.23)
i1.Quantity = 3
i1.Calculate()
' Inserts the item into the array.
Dim items(0) As OrderedItem
items(0) = i1
po.OrderedItems = items
' Calculates the total cost.
Dim subTotal As New Decimal()
Dim oi As OrderedItem
For Each oi In items
subTotal += oi.LineTotal
Next oi
po.SubTotal = subTotal
po.ShipCost = CDec(12.51)
po.TotalCost = po.SubTotal + po.ShipCost
' Serializes the purchase order, and close the TextWriter.
serializer.Serialize(writer, po)
writer.Close()
End Sub
Protected Sub ReadPO(filename As String)
' Creates an instance of the XmlSerializer class;
' specifies the type of object to be deserialized.
Dim serializer As New XmlSerializer(GetType(PurchaseOrder))
' If the XML document has been altered with unknown
' nodes or attributes, handles them with the
' UnknownNode and UnknownAttribute events.
AddHandler serializer.UnknownNode, AddressOf serializer_UnknownNode
AddHandler serializer.UnknownAttribute, AddressOf _
serializer_UnknownAttribute
' A FileStream is needed to read the XML document.
Dim fs As New FileStream(filename, FileMode.Open)
' Declare an object variable of the type to be deserialized.
Dim po As PurchaseOrder
' Uses the Deserialize method to restore the object's state
' with data from the XML document.
po = CType(serializer.Deserialize(fs), PurchaseOrder)
' Reads the order date.
Console.WriteLine(("OrderDate: " & po.OrderDate))
' Reads the shipping address.
Dim shipTo As Address = po.ShipTo
ReadAddress(shipTo, "Ship To:")
' Reads the list of ordered items.
Dim items As OrderedItem() = po.OrderedItems
Console.WriteLine("Items to be shipped:")
Dim oi As OrderedItem
For Each oi In items
Console.WriteLine((ControlChars.Tab & oi.ItemName & _
ControlChars.Tab & _
oi.Description & ControlChars.Tab & oi.UnitPrice & _
ControlChars.Tab & _
oi.Quantity & ControlChars.Tab & oi.LineTotal))
Next oi
' Reads the subtotal, shipping cost, and total cost.
Console.WriteLine((ControlChars.Cr & New String _
(ControlChars.Tab, 5) & _
" Subtotal" & ControlChars.Tab & po.SubTotal & ControlChars.Cr & _
New String(ControlChars.Tab, 5) & " Shipping" & ControlChars.Tab & _
po.ShipCost & ControlChars.Cr & New String(ControlChars.Tab, 5) & _
" Total" & New String(ControlChars.Tab, 2) & po.TotalCost))
End Sub
Protected Sub ReadAddress(a As Address, label As String)
' Reads the fields of the Address.
Console.WriteLine(label)
Console.Write((ControlChars.Tab & a.Name & ControlChars.Cr & _
ControlChars.Tab & a.Line1 & ControlChars.Cr & ControlChars.Tab & _
a.City & ControlChars.Tab & a.State & ControlChars.Cr & _
ControlChars.Tab & a.Zip & ControlChars.Cr))
End Sub
Protected Sub serializer_UnknownNode(sender As Object, e As _
XmlNodeEventArgs)
Console.WriteLine(("Unknown Node:" & e.Name & _
ControlChars.Tab & e.Text))
End Sub
Protected Sub serializer_UnknownAttribute(sender As Object, _
e As XmlAttributeEventArgs)
Dim attr As System.Xml.XmlAttribute = e.Attr
Console.WriteLine(("Unknown attribute " & attr.Name & "='" & _
attr.Value & "'"))
End Sub 'serializer_UnknownAttribute
End Class 'Test
using System;
using System.IO;
using System.Xml;
using System.Xml.Serialization;
// The XmlRoot attribute allows you to set an alternate name
// (PurchaseOrder) for the XML element and its namespace. By
// default, the XmlSerializer uses the class name. The attribute
// also allows you to set the XML namespace for the element. Lastly,
// the attribute sets the IsNullable property, which specifies whether
// the xsi:null attribute appears if the class instance is set to
// a null reference.
[XmlRoot("PurchaseOrder", Namespace="http://www.cpandl.com",
IsNullable = false)]
public class PurchaseOrder
{
public Address ShipTo;
public string OrderDate;
// The XmlArray attribute changes the XML element name
// from the default of "OrderedItems" to "Items".
[XmlArray("Items")]
public OrderedItem[] OrderedItems;
public decimal SubTotal;
public decimal ShipCost;
public decimal TotalCost;
}
public class Address
{
// The XmlAttribute attribute instructs the XmlSerializer to serialize the
// Name field as an XML attribute instead of an XML element (XML element is
// the default behavior).
[XmlAttribute]
public string Name;
public string Line1;
// Setting the IsNullable property to false instructs the
// XmlSerializer that the XML attribute will not appear if
// the City field is set to a null reference.
[XmlElement(IsNullable = false)]
public string City;
public string State;
public string Zip;
}
public class OrderedItem
{
public string ItemName;
public string Description;
public decimal UnitPrice;
public int Quantity;
public decimal LineTotal;
// Calculate is a custom method that calculates the price per item
// and stores the value in a field.
public void Calculate()
{
LineTotal = UnitPrice * Quantity;
}
}
public class Test
{
public static void Main()
{
// Read and write purchase orders.
Test t = new Test();
t.CreatePO("po.xml");
t.ReadPO("po.xml");
}
private void CreatePO(string filename)
{
// Creates an instance of the XmlSerializer class;
// specifies the type of object to serialize.
XmlSerializer serializer = new XmlSerializer(typeof(PurchaseOrder));
TextWriter writer = new StreamWriter(filename);
PurchaseOrder po =new PurchaseOrder();
// Creates an address to ship and bill to.
Address billAddress = new Address();
billAddress.Name = "Teresa Atkinson";
billAddress.Line1 = "1 Main St.";
billAddress.City = "AnyTown";
billAddress.State = "WA";
billAddress.Zip = "00000";
// Sets ShipTo and BillTo to the same addressee.
po.ShipTo = billAddress;
po.OrderDate = System.DateTime.Now.ToLongDateString();
// Creates an OrderedItem.
OrderedItem i1 = new OrderedItem();
i1.ItemName = "Widget S";
i1.Description = "Small widget";
i1.UnitPrice = (decimal) 5.23;
i1.Quantity = 3;
i1.Calculate();
// Inserts the item into the array.
OrderedItem [] items = {i1};
po.OrderedItems = items;
// Calculate the total cost.
decimal subTotal = new decimal();
foreach(OrderedItem oi in items)
{
subTotal += oi.LineTotal;
}
po.SubTotal = subTotal;
po.ShipCost = (decimal) 12.51;
po.TotalCost = po.SubTotal + po.ShipCost;
// Serializes the purchase order, and closes the TextWriter.
serializer.Serialize(writer, po);
writer.Close();
}
protected void ReadPO(string filename)
{
// Creates an instance of the XmlSerializer class;
// specifies the type of object to be deserialized.
XmlSerializer serializer = new XmlSerializer(typeof(PurchaseOrder));
// If the XML document has been altered with unknown
// nodes or attributes, handles them with the
// UnknownNode and UnknownAttribute events.
serializer.UnknownNode+= new
XmlNodeEventHandler(serializer_UnknownNode);
serializer.UnknownAttribute+= new
XmlAttributeEventHandler(serializer_UnknownAttribute);
// A FileStream is needed to read the XML document.
FileStream fs = new FileStream(filename, FileMode.Open);
// Declares an object variable of the type to be deserialized.
PurchaseOrder po;
// Uses the Deserialize method to restore the object's state
// with data from the XML document. */
po = (PurchaseOrder) serializer.Deserialize(fs);
// Reads the order date.
Console.WriteLine ("OrderDate: " + po.OrderDate);
// Reads the shipping address.
Address shipTo = po.ShipTo;
ReadAddress(shipTo, "Ship To:");
// Reads the list of ordered items.
OrderedItem [] items = po.OrderedItems;
Console.WriteLine("Items to be shipped:");
foreach(OrderedItem oi in items)
{
Console.WriteLine("\t"+
oi.ItemName + "\t" +
oi.Description + "\t" +
oi.UnitPrice + "\t" +
oi.Quantity + "\t" +
oi.LineTotal);
}
// Reads the subtotal, shipping cost, and total cost.
Console.WriteLine(
"\n\t\t\t\t\t Subtotal\t" + po.SubTotal +
"\n\t\t\t\t\t Shipping\t" + po.ShipCost +
"\n\t\t\t\t\t Total\t\t" + po.TotalCost
);
}
protected void ReadAddress(Address a, string label)
{
// Reads the fields of the Address.
Console.WriteLine(label);
Console.Write("\t"+
a.Name +"\n\t" +
a.Line1 +"\n\t" +
a.City +"\t" +
a.State +"\n\t" +
a.Zip +"\n");
}
protected void serializer_UnknownNode
(object sender, XmlNodeEventArgs e)
{
Console.WriteLine("Unknown Node:" + e.Name + "\t" + e.Text);
}
protected void serializer_UnknownAttribute
(object sender, XmlAttributeEventArgs e)
{
System.Xml.XmlAttribute attr = e.Attr;
Console.WriteLine("Unknown attribute " +
attr.Name + "='" + attr.Value + "'");
}
}
XML 輸出可能如下所示：
<?xml version="1.0" encoding="utf-8"?>
<PurchaseOrder xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://www.cpandl.com">
<ShipTo Name="Teresa Atkinson">
<Line1>1 Main St.</Line1>
<City>AnyTown</City>
<State>WA</State>
<Zip>00000</Zip>
</ShipTo>
<OrderDate>Wednesday, June 27, 2001</OrderDate>
<Items>
<OrderedItem>
<ItemName>Widget S</ItemName>
<Description>Small widget</Description>
<UnitPrice>5.23</UnitPrice>
<Quantity>3</Quantity>
<LineTotal>15.69</LineTotal>
</OrderedItem>
</Items>
<SubTotal>15.69</SubTotal>
<ShipCost>12.51</ShipCost>
<TotalCost>28.2</TotalCost>
</PurchaseOrder>
