XPathQueryGenerator Classe

Definizione

Quando si specifica una classe che rappresenta un contratto dati e dei metadati che rappresentano un membro del contratto, viene prodotta una query XPath per il membro.When given a class representing a data contract, and metadata representing a member of the contract, produces an XPath query for the member.

public ref class XPathQueryGenerator abstract sealed
public static class XPathQueryGenerator
type XPathQueryGenerator = class
Public Class XPathQueryGenerator
Ereditarietà
XPathQueryGenerator

Esempi

Nell'esempio seguente vengono create query XPath da due classi alle quali sono stati applicati gli attributi DataContractAttribute e DataMemberAttribute.The following example creates XPath queries from two classes to which the DataContractAttribute and DataMemberAttribute attributes have been applied.

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 ulteriori informazioni sui contratti dati, vedere utilizzo di contratti dati.For more information about data contracts, see Using Data Contracts.

L'utilizzo della classe prevede l'esecuzione di quattro passaggi:To use the class, there are four steps:

  1. Creare il tipo di contratto dati applicando DataContractAttribute e DataMemberAttribute al tipo e ai relativi campi o proprietà come appropriato.Create the data contract type by applying the DataContractAttribute and DataMemberAttribute as appropriate to the type and its fields or properties.

  2. Utilizzare il metodo GetMember della classe Type per generare la matrice MemberInfo.Use the GetMember method of the Type class to generate the MemberInfo array.

  3. Passare il tipo e la matrice al metodo.Pass the type and the array to the method.

  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.If needed, use the XmlNamespaceManager returned by the namespaces parameter to examine the XML namespaces referenced by the namespaces prefixes in the XPath query.

Nota

Prefisso dello spazio dei nomi "xg" (per "XPath Generator") viene utilizzato come impostazione predefinita nella query XPath.The namespace prefix "xg" (for "XPath Generator") is used as the default in the XPath. Questo valore non può essere modificato.This cannot be changed. Al contrario, fare riferimento alla raccolta NameTable per conoscere lo spazio dei nomi al quale è associato il prefisso.Instead, refer to the NameTable collection to see what namespace the prefix is associated with.

Metodi

CreateFromDataContractSerializer(Type, MemberInfo[], StringBuilder, XmlNamespaceManager)

Crea una query XPath da un contratto dati utilizzando il tipo di contratto dati, la matrice di elementi dei metadati, l'elemento di primo livello e gli spazi dei nomi specificati.Creates an XPath from a data contract using the specified contract data type, array of metadata elements, the top level element, and namespaces.

CreateFromDataContractSerializer(Type, MemberInfo[], XmlNamespaceManager)

Crea una query XPath da un contratto dati usando il tipo di contratto dati, la matrice di elementi dei metadati e gli spazi dei nomi specificati.Creates an XPath from a data contract using the specified data contract type, array of metadata elements, and namespaces.

Si applica a