HttpWebRequest.ClientCertificates Property

Gets or sets the collection of security certificates that are associated with this request.

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

public X509CertificateCollection ClientCertificates { get; set; }
/** @property */
public X509CertificateCollection get_ClientCertificates ()

/** @property */
public void set_ClientCertificates (X509CertificateCollection value)

public function get ClientCertificates () : X509CertificateCollection

public function set ClientCertificates (value : X509CertificateCollection)

Property Value

The X509CertificateCollection that contains the security certificates associated with this request.

Exception typeCondition


The value specified for a set operation is a null reference (Nothing in Visual Basic).

An application can add a certificate to a collection, but might not have access rights to it. To use a certificate contained in the collection, the application must have the same access rights as the entity that issued the certificate.


The Framework caches SSL sessions as they are created and attempts to reuse a cached session for a new request, if possible. When attempting to reuse an SSL session, the Framework uses the first element of ClientCertificates (if there is one), or tries to reuse an anonymous sessions if ClientCertificates is empty.


For performance reasons, you shouldn't add a client certificate to a HttpWebRequest unless you know the server will ask for it.

For a code example illustrating how to enumerate the certificates in the client certificate store, see the X509Certificate2Collection class.

Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition Platform Note: The Framework attempts to reuse an SSL session only if a client certificate is not required.

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

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