XPathQueryGenerator Classe

Definizione

public ref class XPathQueryGenerator abstract sealed

public static class XPathQueryGenerator

type XPathQueryGenerator = class

Public Class XPathQueryGenerator

Ereditarietà

Object

XPathQueryGenerator

Esempio

Nell'esempio seguente vengono create query XPath da due classi alle quali sono stati applicati gli attributi DataContractAttribute e DataMemberAttribute.

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

namespace GeneratPathExample
{
    class Program
    {
        static void Main(string[] args)
        {
            // Get the type of the class that defines the data contract.
            Type t = typeof(Order);

            // Get the meta data for the specific members to be used in the query.
            MemberInfo[] mi = t.GetMember("Product");
            MemberInfo[] mi2 = t.GetMember("Value");
            MemberInfo[] mi3 = t.GetMember("Quantity");

            // Call the function below to generate and display the query.
            GenerateXPath(t, mi);
            GenerateXPath(t, mi2);
            GenerateXPath(t, mi3);

            // Get the type of the second class that defines a data contract.
            Type t2 = typeof(Line);

            // Get the meta data for the member to be used in the query.
            MemberInfo[] mi4 = t2.GetMember("Items");

            GenerateXPath(t2, mi4);

            Console.ReadLine();
        }

        static void GenerateXPath(Type t, MemberInfo[] mi)
        {

            // Create a new name table and name space manager.
            NameTable nt = new NameTable();
            XmlNamespaceManager xname = new XmlNamespaceManager(nt);

            // Generate the query and print it.
            string query = XPathQueryGenerator.CreateFromDataContractSerializer(
                t, mi, out xname);
            Console.WriteLine(query);
            Console.WriteLine();

            // Display the namespaces and prefixes used in the data contract.
            foreach (string s in xname)
                Console.WriteLine("{0}  = {1}", s, xname.LookupNamespace(s));

            Console.WriteLine();
        }
    }

    [DataContract(Namespace = "http://www.cohowinery.com/")]
    public class Line
    {
        private Order[] itemsValue;

        [DataMember]
        public Order[] Items
        {
            get { return itemsValue; }
            set { itemsValue = value; }
        }
    }

    [DataContract(Namespace = "http://contoso.com")]
    public class Order
    {
        private string productValue;
        private int quantityValue;
        private decimal valueValue;

        [DataMember(Name = "cost")]
        public decimal Value
        {
            get { return valueValue; }
            set { valueValue = value; }
        }

        [DataMember(Name = "quantity")]
        public int Quantity
        {
            get { return quantityValue; }
            set { quantityValue = value; }
        }

        [DataMember(Name = "productName")]
        public string Product
        {
            get { return productValue; }
            set { productValue = value; }
        }
    }
}

Imports System.Collections.Generic
Imports System.Linq
Imports System.Text
Imports System.Reflection
Imports System.Runtime.Serialization
Imports System.Xml

Namespace GeneratPathExample

    Class Program

        Shared Sub Main(ByVal args As String())

            ' Get the type of the class that defines the data contract.
            Dim t As Type = GetType(Order)

            ' Get the meta data for the specific members to be used in the query.
            Dim mi As MemberInfo() = t.GetMember("Product")
            Dim mi2 As MemberInfo() = t.GetMember("Value")
            Dim mi3 As MemberInfo() = t.GetMember("Quantity")

            ' Call the function below to generate and display the query.
            GenerateXPath(t, mi)
            GenerateXPath(t, mi2)
            GenerateXPath(t, mi3)


            ' Get the type of the second class that defines a data contract.
            Dim t2 As Type = GetType(Line)

            ' Get the meta data for the member to be used in the query.
            Dim mi4 As MemberInfo() = t2.GetMember("Items")

            GenerateXPath(t2, mi4)

            Console.ReadLine()
        End Sub

        Shared Sub GenerateXPath(ByVal t As Type, ByVal mi As MemberInfo())


            ' Create a new name table and name space manager.
            Dim nt As New NameTable()
            Dim xname As New XmlNamespaceManager(nt)


            ' Generate the query and print it.
            Dim query As String = XPathQueryGenerator.CreateFromDataContractSerializer( _
                t, mi, xname)
            Console.WriteLine(query)
            Console.WriteLine()


            ' Display the namespaces and prefixes used in the data contract.
            Dim s As String
            For Each s In xname
                Console.WriteLine("{0}  = {1}", s, xname.LookupNamespace(s))
            Next

            Console.WriteLine()

        End Sub
    End Class


    <DataContract(Namespace:="http://www.cohowinery.com/")> _
        Public Class Line

        Private itemsValue As Order()

        <DataMember()>
        Public Property Item() As Order()

            Get
                Return itemsValue
            End Get
            Set(ByVal value As Order())
                itemsValue = value
            End Set
        End Property

    End Class

    <DataContract(Namespace:="http://contoso.com")> _
    Public Class Order

        Private productValue As String
        Private quantityValue As Integer
        Private valueValue As Decimal

        <DataMember(Name:="cost")>
        Public Property Value() As String

            Get
                Return valueValue
            End Get
            Set(ByVal value As String)
                valueValue = value
            End Set
        End Property

        <DataMember(Name:="quantity")> _
        Public Property Quantity() As Integer

            Get
                Return quantityValue
            End Get
            set(ByVal value As Integer)
                quantityValue = value
            End Set
        End Property


        <DataMember(Name:="productName")> _
        Public Property Product() As String

            Get
                Return productValue
            End Get
            Set(ByVal value As String)
                productValue = value
            End Set
        End Property
    End Class
End Namespace

Commenti

Per altre informazioni sui contratti dati, vedere Uso di contratti dati.

L'utilizzo della classe prevede l'esecuzione di quattro passaggi:

1. Creare il tipo di contratto dati applicando DataContractAttribute e DataMemberAttribute al tipo e ai relativi campi o proprietà come appropriato.

2. Utilizzare il metodo GetMember della classe Type per generare la matrice MemberInfo.

3. Passare il tipo e la matrice al metodo.

4. Se necessario, utilizzare l'oggetto XmlNamespaceManager restituito dal parametro namespaces per esaminare gli spazi dei nomi XML ai quali viene fatto riferimento dai prefissi degli spazi dei nomi nella query XPath.

Metodi

Si applica a