XmlDsigXPathTransform 类

定义

public ref class XmlDsigXPathTransform : System::Security::Cryptography::Xml::Transform

public class XmlDsigXPathTransform : System.Security.Cryptography.Xml.Transform

type XmlDsigXPathTransform = class
    inherit Transform

Public Class XmlDsigXPathTransform
Inherits Transform

继承

Object

Transform

XmlDsigXPathTransform

示例

本部分包含两个代码示例。 第一个代码示例演示如何使用 具有信封签名的 XmlDsigXPathTransform 类对 XML 文档进行签名和验证。 此示例对 XML 文档进行签名，并将签名保存在新的 XML 文档中。 第二个代码示例演示如何调用 类的成员 XmlDsigXPathTransform 。

示例 #1

//
// This example signs an XML file using an
// envelope signature. It then verifies the
// signed XML.
//
using System;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Security.Cryptography.Xml;
using System.Text;
using System.Xml;

public class SignVerifyEnvelope
{

    public static void Main(String[] args)
    {
        // Generate a signing key.
        RSA Key = RSA.Create();

        try
        {
            // Create an XML file to sign.
            CreateSomeXml("Example.xml");
            Console.WriteLine("New XML file created.");

            // Sign the XML that was just created and save it in a
            // new file.
            SignXmlFile("Example.xml", "SignedExample.xml", Key, "ancestor-or-self::TempElement");
            Console.WriteLine("XML file signed.");

            // Verify the signature of the signed XML.
            Console.WriteLine("Verifying signature...");
            bool result = VerifyXmlFile("SignedExample.xml");

            // Display the results of the signature verification to \
            // the console.
            if (result)
            {
                Console.WriteLine("The XML signature is valid.");
            }
            else
            {
                Console.WriteLine("The XML signature is not valid.");
            }
        }
        catch (CryptographicException e)
        {
            Console.WriteLine(e.Message);
        }
        finally
        {
            Key.Clear();
        }
    }

    // Sign an XML file and save the signature in a new file.
    public static void SignXmlFile(string FileName, string SignedFileName, RSA Key, string XPathString)
    {
        // Create a new XML document.
        XmlDocument doc = new XmlDocument();

        // Format the document to ignore white spaces.
        doc.PreserveWhitespace = false;

        // Load the passed XML file using it's name.
        doc.Load(new XmlTextReader(FileName));

        // Create a SignedXml object.
        SignedXml signedXml = new SignedXml(doc);

        // Add the key to the SignedXml document.
        signedXml.SigningKey = Key;

        // Create a reference to be signed.
        Reference reference = new Reference();
        reference.Uri = "";

        // Create an XmlDsigXPathTransform object using
        // the helper method 'CreateXPathTransform' defined
        // later in this sample.

        XmlDsigXPathTransform XPathTransform = CreateXPathTransform(XPathString);

        // Add the transform to the reference.
        reference.AddTransform(XPathTransform);

        // Add the reference to the SignedXml object.
        signedXml.AddReference(reference);

        // Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate).
        KeyInfo keyInfo = new KeyInfo();
        keyInfo.AddClause(new RSAKeyValue((RSA)Key));
        signedXml.KeyInfo = keyInfo;

        // Compute the signature.
        signedXml.ComputeSignature();

        // Get the XML representation of the signature and save
        // it to an XmlElement object.
        XmlElement xmlDigitalSignature = signedXml.GetXml();

        // Append the element to the XML document.
        doc.DocumentElement.AppendChild(doc.ImportNode(xmlDigitalSignature, true));

        // Save the signed XML document to a file specified
        // using the passed string.
        XmlTextWriter xmltw = new XmlTextWriter(SignedFileName, new UTF8Encoding(false));
        doc.WriteTo(xmltw);
        xmltw.Close();
    }
    // Verify the signature of an XML file and return the result.
    public static Boolean VerifyXmlFile(String Name)
    {
        // Create a new XML document.
        XmlDocument xmlDocument = new XmlDocument();

        // Format using white spaces.
        xmlDocument.PreserveWhitespace = true;

        // Load the passed XML file into the document.
        xmlDocument.Load(Name);

        // Create a new SignedXml object and pass it
        // the XML document class.
        SignedXml signedXml = new SignedXml(xmlDocument);

        // Find the "Signature" node and create a new
        // XmlNodeList object.
        XmlNodeList nodeList = xmlDocument.GetElementsByTagName("Signature");

        // Load the signature node.
        signedXml.LoadXml((XmlElement)nodeList[0]);

        // Check the signature and return the result.
        return signedXml.CheckSignature();
    }

    // Create the XML that represents the transform.
    private static XmlDsigXPathTransform CreateXPathTransform(string XPathString)
    {
        // Create a new XMLDocument object.
        XmlDocument doc = new XmlDocument();

        // Create a new XmlElement.
        XmlElement xPathElem = doc.CreateElement("XPath");

        // Set the element text to the value
        // of the XPath string.
        xPathElem.InnerText = XPathString;

        // Create a new XmlDsigXPathTransform object.
        XmlDsigXPathTransform xForm = new XmlDsigXPathTransform();

        // Load the XPath XML from the element.
        xForm.LoadInnerXml(xPathElem.SelectNodes("."));

        // Return the XML that represents the transform.
        return xForm;
    }

    // Create example data to sign.
    public static void CreateSomeXml(string FileName)
    {
        // Create a new XmlDocument object.
        XmlDocument document = new XmlDocument();

        // Create a new XmlNode object.
        XmlNode node = document.CreateNode(XmlNodeType.Element, "", "MyXML", "Don't_Sign");

        // Append the node to the document.
        document.AppendChild(node);

        // Create a new XmlNode object.
        XmlNode subnode = document.CreateNode(XmlNodeType.Element, "", "TempElement", "Sign");

        // Add some text to the node.
        subnode.InnerText = "Here is some data to sign.";

        // Append the node to the document.
        document.DocumentElement.AppendChild(subnode);

        // Save the XML document to the file name specified.
        XmlTextWriter xmltw = new XmlTextWriter(FileName, new UTF8Encoding(false));
        document.WriteTo(xmltw);
        xmltw.Close();
    }
}

'
' This example signs an XML file using an
' envelope signature. It then verifies the 
' signed XML.
'
Imports System.Security.Cryptography
Imports System.Security.Cryptography.X509Certificates
Imports System.Security.Cryptography.Xml
Imports System.Text
Imports System.Xml



Module SignVerifyEnvelope


    Sub Main(ByVal args() As String)
        ' Generate a signing key.
        Dim Key As RSA = RSA.Create()

        Try
            ' Create an XML file to sign.
            CreateSomeXml("Example.xml")
            Console.WriteLine("New XML file created.")

            ' Sign the XML that was just created and save it in a 
            ' new file.
            SignXmlFile("Example.xml", "SignedExample.xml", Key, "ancestor-or-self::TempElement")
            Console.WriteLine("XML file signed.")

            ' Verify the signature of the signed XML.
            Console.WriteLine("Verifying signature...")
            Dim result As Boolean = VerifyXmlFile("SignedExample.xml")

            ' Display the results of the signature verification to \
            ' the console.
            If result Then
                Console.WriteLine("The XML signature is valid.")
            Else
                Console.WriteLine("The XML signature is not valid.")
            End If
        Catch e As CryptographicException
            Console.WriteLine(e.Message)
        Finally
            Key.Clear()
        End Try

    End Sub


    ' Sign an XML file and save the signature in a new file.
    Sub SignXmlFile(ByVal FileName As String, ByVal SignedFileName As String, ByVal Key As RSA, ByVal XPathString As String)
        ' Create a new XML document.
        Dim doc As New XmlDocument()

        ' Format the document to ignore white spaces.
        doc.PreserveWhitespace = False

        ' Load the passed XML file using it's name.
        doc.Load(New XmlTextReader(FileName))

        ' Create a SignedXml object.
        Dim signedXml As New SignedXml(doc)

        ' Add the key to the SignedXml document. 
        signedXml.SigningKey = Key

        ' Create a reference to be signed.
        Dim reference As New Reference()
        reference.Uri = ""

        ' Create an XmlDsigXPathTransform object using 
        ' the helper method 'CreateXPathTransform' defined
        ' later in this sample.
        Dim XPathTransform As XmlDsigXPathTransform = CreateXPathTransform(XPathString)

        ' Add the transform to the reference.
        reference.AddTransform(XPathTransform)

        ' Add the reference to the SignedXml object.
        signedXml.AddReference(reference)

        ' Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate).
        Dim keyInfo As New KeyInfo()
        keyInfo.AddClause(New RSAKeyValue(CType(Key, RSA)))
        signedXml.KeyInfo = keyInfo

        ' Compute the signature.
        signedXml.ComputeSignature()

        ' Get the XML representation of the signature and save
        ' it to an XmlElement object.
        Dim xmlDigitalSignature As XmlElement = signedXml.GetXml()

        ' Append the element to the XML document.
        doc.DocumentElement.AppendChild(doc.ImportNode(xmlDigitalSignature, True))

        ' Save the signed XML document to a file specified
        ' using the passed string.
        Dim xmltw As New XmlTextWriter(SignedFileName, New UTF8Encoding(False))
        doc.WriteTo(xmltw)
        xmltw.Close()

    End Sub

    ' Verify the signature of an XML file and return the result.
    Function VerifyXmlFile(ByVal Name As String) As [Boolean]
        ' Create a new XML document.
        Dim xmlDocument As New XmlDocument()

        ' Format using white spaces.
        xmlDocument.PreserveWhitespace = True

        ' Load the passed XML file into the document. 
        xmlDocument.Load(Name)

        ' Create a new SignedXml object and pass it
        ' the XML document class.
        Dim signedXml As New SignedXml(xmlDocument)

        ' Find the "Signature" node and create a new
        ' XmlNodeList object.
        Dim nodeList As XmlNodeList = xmlDocument.GetElementsByTagName("Signature")

        ' Load the signature node.
        signedXml.LoadXml(CType(nodeList(0), XmlElement))

        ' Check the signature and return the result.
        Return signedXml.CheckSignature()

    End Function


    ' Create the XML that represents the transform.
    Function CreateXPathTransform(ByVal XPathString As String) As XmlDsigXPathTransform
        ' Create a new XMLDocument object.
        Dim doc As New XmlDocument()

        ' Create a new XmlElement.
        Dim xPathElem As XmlElement = doc.CreateElement("XPath")

        ' Set the element text to the value
        ' of the XPath string.
        xPathElem.InnerText = XPathString

        ' Create a new XmlDsigXPathTransform object.
        Dim xForm As New XmlDsigXPathTransform()

        ' Load the XPath XML from the element. 
        xForm.LoadInnerXml(xPathElem.SelectNodes("."))

        ' Return the XML that represents the transform.
        Return xForm

    End Function


    ' Create example data to sign.
    Sub CreateSomeXml(ByVal FileName As String)
        ' Create a new XmlDocument object.
        Dim document As New XmlDocument()

        ' Create a new XmlNode object.
        Dim node As XmlNode = document.CreateNode(XmlNodeType.Element, "", "MyXML", "Don't_Sign")

        ' Append the node to the document.
        document.AppendChild(node)

        ' Create a new XmlNode object.
        Dim subnode As XmlNode = document.CreateNode(XmlNodeType.Element, "", "TempElement", "Sign")

        ' Add some text to the node.
        subnode.InnerText = "Here is some data to sign."

        ' Append the node to the document.
        document.DocumentElement.AppendChild(subnode)

        ' Save the XML document to the file name specified.
        Dim xmltw As New XmlTextWriter(FileName, New UTF8Encoding(False))
        document.WriteTo(xmltw)
        xmltw.Close()

    End Sub
End Module

示例 #2

using System;
using System.IO;
using System.Xml;
using System.Security.Cryptography;
using System.Security.Cryptography.Xml;

class Class1
{
    [STAThread]
    static void Main(string[] args)
    {
        // Encrypt a sample XML string.
        XmlDocument productsXml = LoadProducts();
        ShowTransformProperties(productsXml);

        // Encrypt an XPath Xml string.
        XmlDocument transformXml = LoadTransformByXml();
        ShowTransformProperties(transformXml);

        // Use XmlDsigXPathTransform to resolve a Uri.
        Uri baseUri = new Uri("http://www.contoso.com");
        string relativeUri = "xml";
        Uri absoluteUri = ResolveUris(baseUri, relativeUri);

        Console.WriteLine("This sample completed successfully; " +
            "press Enter to exit.");
        Console.ReadLine();
    }

    // Encrypt the text in the specified XmlDocument.
    private static void ShowTransformProperties(XmlDocument xmlDoc)
    {

        // Create a new XMLDocument object.
        XmlDocument doc = new XmlDocument();

        // Create a new XmlElement.
        XmlElement xPathElem = doc.CreateElement("XPath");

        // Set the element text to the value
        // of the XPath string.
        xPathElem.InnerText = "ancestor-or-self::PRODUCTS";

        // Create a new XmlDsigXPathTransform object.
        XmlDsigXPathTransform xmlTransform = new XmlDsigXPathTransform();

        // Load the XPath XML from the element. 
        xmlTransform.LoadInnerXml(xPathElem.SelectNodes("."));

        // Ensure the transform is using the proper algorithm.
        xmlTransform.Algorithm =
            SignedXml.XmlDsigXPathTransformUrl;

        // Retrieve the XML representation of the current transform.
        XmlElement xmlInTransform = xmlTransform.GetXml();

        Console.WriteLine("\nXml representation of the current transform: ");
        Console.WriteLine(xmlInTransform.OuterXml);

        // Retrieve the valid input types for the current transform.
        Type[] validInTypes = xmlTransform.InputTypes;

        // Verify the xmlTransform can accept the XMLDocument as an
        // input type.
        for (int i = 0; i < validInTypes.Length; i++)
        {
            if (validInTypes[i] == xmlDoc.GetType())
            {
                // Load the document into the transfrom.
                xmlTransform.LoadInput(xmlDoc);

                try
                {
                    // This transform is created for demonstration purposes.
                    XmlDsigXPathTransform secondTransform =
                        new XmlDsigXPathTransform();

                    string classDescription = secondTransform.ToString();

                    xmlTransform.LoadInnerXml(xPathElem.SelectNodes(".")); ;
                }
                catch (CryptographicException)
                {
                    Console.WriteLine("Caught exception while trying to " +
                        "load the specified Xml document. The document " +
                        "requires an XPath element to be valid.");
                }
                break;
            }
        }

        Type[] validOutTypes = xmlTransform.OutputTypes;

        for (int i = validOutTypes.Length - 1; i >= 0; i--)
        {
            if (validOutTypes[i] == typeof(System.Xml.XmlDocument))
            {
                try
                {
                    Type xmlDocumentType = typeof(System.Xml.XmlDocument);
                    XmlDocument xmlDocumentOutput = (XmlDocument)
                        xmlTransform.GetOutput(xmlDocumentType);

                    // Display to the console the Xml before and after
                    // encryption.
                    Console.WriteLine("Result of the GetOutput method call" +
                        " from the current transform: " +
                        xmlDocumentOutput.OuterXml);
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Unexpected exception caught: " +
                        ex.ToString());
                }

                break;
            }
            else if (validOutTypes[i] == typeof(System.Xml.XmlNodeList))
            {
                try
                {
                    Type xmlNodeListType = typeof(System.Xml.XmlNodeList);
                    XmlNodeList xmlNodes = (XmlNodeList)
                        xmlTransform.GetOutput(xmlNodeListType);

                    // Display to the console the Xml before and after
                    // encryption.
                    Console.WriteLine("Encoding the following message: " +
                        xmlDoc.InnerText);

                    Console.WriteLine("Nodes of the XmlNodeList retrieved " +
                        "from GetOutput:");
                    for (int j = 0; j < xmlNodes.Count; j++)
                    {
                        Console.WriteLine("Node " + j +
                            " has the following name: " +
                            xmlNodes.Item(j).Name +
                            " and the following InnerXml: " +
                            xmlNodes.Item(j).InnerXml);
                    }
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Unexpected exception caught: " +
                        ex.ToString());
                }

                break;
            }
            else
            {
                object outputObject = xmlTransform.GetOutput();
            }
        }
    }

    // Create an XML document for the dsig namespace.
    private static XmlDocument LoadTransformByXml()
    {
        XmlDocument xmlDoc = new XmlDocument();

        string transformXml = "<Signature><Reference URI=''><Transforms>";
        transformXml += "<Transform><XPath ";
        transformXml += "xmlns:dsig='http://www.w3.org/2000/09/xmldsig#'>";
        transformXml += "not(ancestor-or-self::dsig:Signature)";
        transformXml += "</XPath></Transform>";
        transformXml += "</Transforms></Reference></Signature>";

        xmlDoc.LoadXml(transformXml);
        return xmlDoc;
    }

    // Create an XML document describing various products.
    private static XmlDocument LoadProducts()
    {
        XmlDocument xmlDoc = new XmlDocument();

        string contosoProducts = "<PRODUCTS>";
        contosoProducts += "<PRODUCT><ID>123</ID>";
        contosoProducts += "<DESCRIPTION>Router</DESCRIPTION></PRODUCT>";
        contosoProducts += "<PRODUCT><ID>456</ID>";
        contosoProducts += "<DESCRIPTION>Keyboard</DESCRIPTION></PRODUCT>";
        contosoProducts += "<PRODUCT><ID>789</ID>";
        contosoProducts += "<DESCRIPTION>Monitor</DESCRIPTION></PRODUCT>";
        contosoProducts += "</PRODUCTS>";

        xmlDoc.LoadXml(contosoProducts);
        return xmlDoc;
    }

    // Resolve the specified base and relative Uri's .
    private static Uri ResolveUris(Uri baseUri, string relativeUri)
    {
        XmlUrlResolver xmlResolver = new XmlUrlResolver();
        xmlResolver.Credentials =
            System.Net.CredentialCache.DefaultCredentials;

        XmlDsigXPathTransform xmlTransform =
            new XmlDsigXPathTransform();
        xmlTransform.Resolver = xmlResolver;

        Uri absoluteUri = xmlResolver.ResolveUri(baseUri, relativeUri);

        if (absoluteUri != null)
        {
            Console.WriteLine(
                "\nResolved the base Uri and relative Uri to the following:");
            Console.WriteLine(absoluteUri.ToString());
        }
        else
        {
            Console.WriteLine(
                "Unable to resolve the base Uri and relative Uri");
        }
        return absoluteUri;
    }
}

Imports System.IO
Imports System.Xml
Imports System.Security.Cryptography
Imports System.Security.Cryptography.Xml



Class Class1

    <STAThread()> _
    Shared Sub Main(ByVal args() As String)
        ' Encrypt a sample XML string.
        Dim productsXml As XmlDocument = LoadProducts()
        ShowTransformProperties(productsXml)

        ' Encrypt an XPath Xml string.
        Dim transformXml As XmlDocument = LoadTransformByXml()
        ShowTransformProperties(transformXml)

        ' Use XmlDsigXPathTransform to resolve a Uri.
        Dim baseUri As New Uri("http://www.contoso.com")
        Dim relativeUri As String = "xml"
        Dim absoluteUri As Uri = ResolveUris(baseUri, relativeUri)

        Console.WriteLine("This sample completed successfully; " + "press Enter to exit.")
        Console.ReadLine()

    End Sub


    ' Encrypt the text in the specified XmlDocument.
    Private Shared Sub ShowTransformProperties(ByVal xmlDoc As XmlDocument)
        ' Create a new XMLDocument object.
        Dim doc As New XmlDocument()

        ' Create a new XmlElement.
        Dim xPathElem As XmlElement = doc.CreateElement("XPath")

        ' Set the element text to the value
        ' of the XPath string.
        xPathElem.InnerText = "ancestor-or-self::PRODUCTS"

        ' Create a new XmlDsigXPathTransform object.
        Dim xmlTransform As New XmlDsigXPathTransform()

        ' Load the XPath XML from the element. 
        xmlTransform.LoadInnerXml(xPathElem.SelectNodes("."))
        ' Ensure the transform is using the proper algorithm.
        xmlTransform.Algorithm = SignedXml.XmlDsigXPathTransformUrl
        ' Retrieve the XML representation of the current transform.
        Dim xmlInTransform As XmlElement = xmlTransform.GetXml()
        Console.WriteLine(vbLf + "Xml representation of the current transform: ")
        Console.WriteLine(xmlInTransform.OuterXml)

        ' Retrieve the valid input types for the current transform.
        Dim validInTypes As Type() = xmlTransform.InputTypes
        ' Verify the xmlTransform can accept the XMLDocument as an
        ' input type.
        Dim i As Integer
        For i = 0 To validInTypes.Length
            If validInTypes(i).Equals(xmlDoc.GetType()) Then
                ' Load the document into the transfrom.
                xmlTransform.LoadInput(xmlDoc)
                Try
                    ' This transform is created for demonstration purposes.
                    Dim secondTransform As New XmlDsigXPathTransform()

                    Dim classDescription As String = secondTransform.ToString()
                    xmlTransform.LoadInnerXml(xPathElem.SelectNodes("."))
                Catch
                    Console.WriteLine("Caught exception while trying to " + "load the specified Xml document. The document " + "requires an XPath element to be valid.")
                End Try
                Exit For
            End If
        Next i

        Dim validOutTypes As Type() = xmlTransform.OutputTypes
        For i = validOutTypes.Length - 1 To 0 Step -1
            If validOutTypes(i).Equals(GetType(System.Xml.XmlDocument)) Then
                Try
                    Dim xmlDocumentType As Type = GetType(System.Xml.XmlDocument)
                    Dim xmlDocumentOutput As XmlDocument = CType(xmlTransform.GetOutput(xmlDocumentType), XmlDocument)
                    ' Display to the console the Xml before and after
                    ' encryption.
                    Console.WriteLine("Result of the GetOutput method call" + " from the current transform: " + xmlDocumentOutput.OuterXml)
                Catch ex As Exception
                    Console.WriteLine("Unexpected exception caught: " + ex.ToString())
                End Try

                Exit For
            ElseIf validOutTypes(i).Equals(GetType(System.Xml.XmlNodeList)) Then
                Try
                    Dim xmlNodeListType As Type = GetType(System.Xml.XmlNodeList)
                    Dim xmlNodes As XmlNodeList = CType(xmlTransform.GetOutput(xmlNodeListType), XmlNodeList)

                    ' Display to the console the Xml before and after
                    ' encryption.
                    Console.WriteLine("Encoding the following message: " + xmlDoc.InnerText)

                    Console.WriteLine("Nodes of the XmlNodeList retrieved " + "from GetOutput:")
                    For j As Integer = 0 To xmlNodes.Count - 1
                        Console.WriteLine("Node " + j + " has the following name: " + xmlNodes.Item(j).Name + " and the following InnerXml: " + xmlNodes.Item(j).InnerXml)
                    Next
                Catch ex As Exception
                    Console.WriteLine("Unexpected exception caught: " + ex.ToString())
                End Try

                Exit For
            Else
                Dim outputObject As Object = xmlTransform.GetOutput()
            End If 
        Next i

    End Sub


    ' Create an XML document for the dsig namespace.
    Private Shared Function LoadTransformByXml() As XmlDocument
        Dim xmlDoc As New XmlDocument()

        Dim transformXml As String = "<Signature><Reference URI=''><Transforms>"
        transformXml += "<Transform><XPath "
        transformXml += "xmlns:dsig='http://www.w3.org/2000/09/xmldsig#'>"
        transformXml += "not(ancestor-or-self::dsig:Signature)"
        transformXml += "</XPath></Transform>"
        transformXml += "</Transforms></Reference></Signature>"

        xmlDoc.LoadXml(transformXml)
        Return xmlDoc

    End Function 'LoadTransformByXml


    ' Create an XML document describing various products.
    Private Shared Function LoadProducts() As XmlDocument
        Dim xmlDoc As New XmlDocument()

        Dim contosoProducts As String = "<PRODUCTS>"
        contosoProducts += "<PRODUCT><ID>123</ID>"
        contosoProducts += "<DESCRIPTION>Router</DESCRIPTION></PRODUCT>"
        contosoProducts += "<PRODUCT><ID>456</ID>"
        contosoProducts += "<DESCRIPTION>Keyboard</DESCRIPTION></PRODUCT>"
        contosoProducts += "<PRODUCT><ID>789</ID>"
        contosoProducts += "<DESCRIPTION>Monitor</DESCRIPTION></PRODUCT>"
        contosoProducts += "</PRODUCTS>"

        xmlDoc.LoadXml(contosoProducts)
        Return xmlDoc

    End Function 'LoadProducts


    ' Resolve the specified base and relative Uri's .
    Private Shared Function ResolveUris(ByVal baseUri As Uri, ByVal relativeUri As String) As Uri
        Dim xmlResolver As New XmlUrlResolver()
        xmlResolver.Credentials = System.Net.CredentialCache.DefaultCredentials

        Dim xmlTransform As New XmlDsigXPathTransform()
        xmlTransform.Resolver = xmlResolver
        Dim absoluteUri As Uri = xmlResolver.ResolveUri(baseUri, relativeUri)

        If Not (absoluteUri Is Nothing) Then
            Console.WriteLine(vbLf + "Resolved the base Uri and relative Uri to the following:")
            Console.WriteLine(absoluteUri.ToString())
        Else
            Console.WriteLine("Unable to resolve the base Uri and relative Uri")
        End If
        Return absoluteUri

    End Function
End Class

注解

类 XmlDsigXPathTransform 允许使用 XPath 语言对 XML 文档进行寻址。 此类使用 XPath 表达式选择要签名或加密的 XML 节点，同时从任一加密操作中删除所有其他节点。

XmlDsigXPathTransform使用 类使用 XPath 表达式对 XML 文档的特定部分进行签名或加密。 有关将 XmlDsigXPathTransform 类初始化为 XPath 转换字符串值的信息，请参阅 LoadInnerXml 方法。

描述 XmlDsigXPathTransform 类的统一资源标识符 (URI) 由 XmlDsigXPathTransformUrl 字段定义。

有关 XPath 转换的详细信息，请参阅 W3C XMLDSIG 规范的第 6.6.3 节。