批注使您能够在不修改基础架构的情况下修改类型化 DataSet 中元素的名称。如果修改基础架构中元素的名称，则会使类型化 DataSet 引用不存在于数据源中的对象，并且会丢失对存在于数据源中的对象的引用。

　　利用批注，您可以使用更有意义的名称来自定义类型化 DataSet 中对象的名称，从而使代码更易于阅读，类型化 DataSet 更易于为客户端使用，同时保持基础架构不变。例如，Northwind 数据库中 Customers 表的以下架构元素会生成 CustomersRow 这一 DataRow 对象名称和一个名为 Customers 的 DataRowCollection。

<xs:element name="Customers"><xs:complexType><xs:sequence><xs:element name="CustomerID" type="xs:string" minOccurs="0" /></xs:sequence></xs:complexType>
</xs:element>

DataRowCollection 名称 Customers 在客户端代码中是有意义的，但 DataRow 名称 CustomersRow 则会导致误解，因为它是单个对象。此外，在通常情况下，将不使用 Row 标识符来引用该对象，而仅将该对象当作 Customer 对象来引用。解决方案是批注架构并标识 DataRow 和 DataRowCollection 对象的新名称。下面是上一架构的批注版本。

<xs:element name="Customers" codegen:typedName="Customer" codegen:typedPlural="Customers"><xs:complexType><xs:sequence><xs:element name="CustomerID" type="xs:string" minOccurs="0" /></xs:sequence></xs:complexType>
</xs:element>

将 Customer 的值指定为 typedName 将生成 DataRow 对象名称 Customer。将 Customers 的值指定为 typedPlural 则会保留 DataRowCollection 名称 Customers。

下表显示可用的批注。

下表显示可为 nullValue 批注指定的值。

下表显示类型化 DataSet 中对象的默认值以及可用的批注。

若要使用类型化 DataSet 批注，则必须在 XML 架构定义语言 (XSD) 架构中包含以下 xmlns 引用。

xmlns:codegen="urn:schemas-microsoft-com:xml-msprop"

下面是一个批注架构示例，它公开 Northwind 数据库的 Customers 表并包含与 Orders 表的关系。

<?xml version="1.0" encoding="utf-8"?>
<xs:schema id="CustomerDataSet" xmlns:codegen="urn:schemas-microsoft-com:xml-msprop"xmlns="" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata"><xs:element name="CustomerDataSet" msdata:IsDataSet="true"><xs:complexType><xs:choice maxOccurs="unbounded"><xs:element name="Customers" codegen:typedName="Customer" codegen:typedPlural="Customers"><xs:complexType><xs:sequence><xs:element name="CustomerID" codegen:typedName="CustomerID" type="xs:string" minOccurs="0" /><xs:element name="CompanyName" codegen:typedName="CompanyName" type="xs:string" minOccurs="0" /><xs:element name="Phone" codegen:typedName="Phone" codegen:nullValue="" type="xs:string" minOccurs="0" /></xs:sequence></xs:complexType></xs:element><xs:element name="Orders" codegen:typedName="Order" codegen:typedPlural="Orders"><xs:complexType><xs:sequence><xs:element name="OrderID" codegen:typedName="OrderID" type="xs:int" minOccurs="0" /><xs:element name="CustomerID" codegen:typedName="CustomerID" codegen:nullValue="" type="xs:string" minOccurs="0" /><xs:element name="EmployeeID" codegen:typedName="EmployeeID" codegen:nullValue="0" type="xs:int" minOccurs="0" /><xs:element name="OrderDate" codegen:typedName="OrderDate" codegen:nullValue="1980-01-01T00:00:00" type="xs:dateTime" minOccurs="0" /></xs:sequence></xs:complexType></xs:element></xs:choice></xs:complexType><xs:unique name="Constraint1"><xs:selector xpath=".//Customers" /><xs:field xpath="CustomerID" /></xs:unique><xs:keyref name="CustOrders" refer="Constraint1" codegen:typedParent="Customer" codegen:typedChildren="GetOrders"><xs:selector xpath=".//Orders" /><xs:field xpath="CustomerID" /></xs:keyref></xs:element>
</xs:schema>

以下代码示例使用从示例架构创建的强类型 DataSet。它使用一个 DataAdapter 填充 Customers 表，并使用另一个 DataAdapter 填充 Orders 表。强类型 DataSet 定义 DataRelations。

[Visual Basic]
Dim nwindConn As SqlConnection = New SqlConnection("Data Source=localhost;Integrated Security=SSPI;" & _"Initial Catalog=northwind")
Dim custDA As SqlDataAdapter = New SqlDataAdapter("SELECT CustomerID, CompanyName, Phone FROM Customers", &nwindConn)
Dim orderDA As SqlDataAdapter = New SqlDataAdapter("SELECT OrderID, CustomerID, EmployeeID, OrderDate FROM Orders", &nwindConn)
' Populate a strongly typed DataSet.
nwindConn.Open()
Dim custDS As CustomerDataSet = New CustomerDataSet()
custDA.Fill(custDS, "Customers")
orderDA.Fill(custDS, "Orders")
nwindConn.Close()
' Add a strongly typed event.
AddHandler custDS.Customers.CustomerChanged, &New CustomerDataSet.CustomerChangeEventHandler(AddressOf OnCustomerChanged)
' Add a strongly typed DataRow.
Dim newCust As CustomerDataSet.Customer = custDS.Customers.NewCustomer()
newCust.CustomerID = "NEW01"
newCust.CompanyName = "My New Company"
custDS.Customers.AddCustomer(newCust)
' Navigate the child relation.
Dim customer As CustomerDataSet.Customer
Dim order As CustomerDataSet.Order
For Each customer In custDS.CustomersConsole.WriteLine(customer.CustomerID)For Each order In customer.GetOrders()Console.WriteLine(vbTab & order.OrderID)Next
Next
Private Shared Sub OnCustomerChanged(sender As Object, e As CustomerDataSet.CustomerChangeEvent)
End Sub

[C#]
SqlConnection nwindConn = new SqlConnection("Data Source=localhost;Integrated Security=SSPI;Initial Catalog=northwind");
SqlDataAdapter custDA = new SqlDataAdapter("SELECT CustomerID, CompanyName, Phone FROM Customers", nwindConn);
SqlDataAdapter orderDA = new SqlDataAdapter("SELECT OrderID, CustomerID, EmployeeID, OrderDate FROM Orders", nwindConn);
// Populate a strongly typed DataSet.
nwindConn.Open();
CustomerDataSet custDS = new CustomerDataSet();
custDA.Fill(custDS, "Customers");
orderDA.Fill(custDS, "Orders");
nwindConn.Close();
// Add a strongly typed event.
custDS.Customers.CustomerChanged += new CustomerDataSet.CustomerChangeEventHandler(OnCustomerChanged);
// Add a strongly typed DataRow.
CustomerDataSet.Customer newCust = custDS.Customers.NewCustomer();
newCust.CustomerID = "NEW01";
newCust.CompanyName = "My New Company";
custDS.Customers.AddCustomer(newCust);
// Navigate the child relation.
foreach(CustomerDataSet.Customer customer in custDS.Customers)
{Console.WriteLine(customer.CustomerID);foreach(CustomerDataSet.Order order in customer.GetOrders())Console.WriteLine("\t" + order.OrderID);
}
protected static void OnCustomerChanged(object sender, CustomerDataSet.CustomerChangeEvent e)
{
}