LocalCertificateSelectionCallback Delegate


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Selects the local Secure Sockets Layer (SSL) certificate used for authentication.

Namespace:   System.Net.Security
Assembly:  System (in System.dll)

public delegate X509Certificate LocalCertificateSelectionCallback(
	object sender,
	string targetHost,
	X509CertificateCollection localCertificates,
	X509Certificate remoteCertificate,
	string[] acceptableIssuers


Type: System.Object

An object that contains state information for this validation.

Type: System.String

The host server specified by the client.

Type: System.Security.Cryptography.X509Certificates.X509CertificateCollection

An X509CertificateCollection containing local certificates.

Type: System.Security.Cryptography.X509Certificates.X509Certificate

The certificate used to authenticate the remote party.

Type: System.String[]

A String array of certificate issuers acceptable to the remote party.

Return Value

Type: System.Security.Cryptography.X509Certificates.X509Certificate

An X509Certificate used for establishing an SSL connection.

This delegate is used to construct instances of the SslStream class. The SslStream class is used to help secure information exchanged between a client and server. The client and server use this delegate to select a certificate to be used for authentication.

The following code example demonstrates a method implementation for this delegate.

public static X509Certificate SelectLocalCertificate(
    object sender,
    string targetHost, 
    X509CertificateCollection localCertificates, 
    X509Certificate remoteCertificate, 
    string[] acceptableIssuers)
    Console.WriteLine("Client is selecting a local certificate.");
    if (acceptableIssuers != null && 
        acceptableIssuers.Length > 0 &&
        localCertificates != null &&
        localCertificates.Count > 0)
        // Use the first certificate that is from an acceptable issuer.
        foreach (X509Certificate certificate in localCertificates)
            string issuer = certificate.Issuer;
            if (Array.IndexOf(acceptableIssuers, issuer) != -1)
                return certificate;
    if (localCertificates != null &&
        localCertificates.Count > 0)
        return localCertificates[0];

    return null;

The following code example demonstrates creating an instance of this delegate.

// Server name must match the host name and the name on the host's certificate. 
serverName = args[0];
// Create a TCP/IP client socket.
TcpClient client = new TcpClient(serverName,80);
Console.WriteLine("Client connected.");
// Create an SSL stream that will close the client's stream.
SslStream sslStream = new SslStream(
    new RemoteCertificateValidationCallback (ValidateServerCertificate), 
    new LocalCertificateSelectionCallback(SelectLocalCertificate)

.NET Framework
Available since 2.0
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