NegotiateStream.AuthenticateAsClientAsync Method (NetworkCredential, ChannelBinding, String)

.NET Framework (current version)

Called by clients to authenticate the client, and optionally the server, in a client-server connection as an asynchronous operation. The authentication process uses the specified client credential and the channel binding.

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

[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public virtual Task AuthenticateAsClientAsync(
	NetworkCredential credential,
	ChannelBinding binding,
	string targetName


Type: System.Net.NetworkCredential

The NetworkCredential that is used to establish the identity of the client.

Type: System.Security.Authentication.ExtendedProtection.ChannelBinding

The ChannelBinding that is used for extended protection.

Type: System.String

The Service Principal Name (SPN) that uniquely identifies the server to authenticate.

Return Value

Type: System.Threading.Tasks.Task

Returns Task

The task object representing the asynchronous operation.

Exception Condition

targetName is null.

- or -

credential is null.


The authentication failed. You can use this object to retry the authentication.


The authentication failed. You can use this object to retry the authentication.


Authentication has already occurred.

- or -

This stream was used previously to attempt authentication as the server. You cannot use the stream to retry authentication as the client.


This object has been closed.

The impersonation level is Identification, the security level is EncryptAndSign, and mutual authentication is requested. The NegotiateStream class will construct the SPN used for mutual authentication.

The ChannelBinding used for extended protection that is passed to this method in the binding parameter would be retrieved by an application from TransportContext property on the associated SslStream.

When authentication succeeds, you must check the IsEncrypted and IsSigned properties to determine what security services are used by the NegotiateStream. Check the IsMutuallyAuthenticated property to determine whether mutual authentication occurred.

.NET Framework
Available since 4.5
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