HttpWebRequest.ClientCertificates Property


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

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

member ClientCertificates : X509CertificateCollection with get, set

Property Value

Type: System.Security.Cryptography.X509Certificates.X509CertificateCollection

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

Exception Condition

The value specified for a set operation is null.

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.


The Framework attempts to reuse an SSL session only if a client certificate is not required.

.NET Framework
Available since 1.1
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