This documentation is archived and is not being maintained.

NegotiateStream.BeginAuthenticateAsClient Method (NetworkCredential, ChannelBinding, String, AsyncCallback, Object)

Called by clients to begin an asynchronous operation to authenticate the client, and optionally the server, in a client-server connection. The authentication process uses the specified credentials and channel binding. This method does not block.

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

[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public virtual IAsyncResult BeginAuthenticateAsClient(
	NetworkCredential credential,
	ChannelBinding binding,
	string targetName,
	AsyncCallback asyncCallback,
	Object asyncState


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.
Type: System.AsyncCallback
An AsyncCallback delegate that references the method to invoke when the authentication is complete.
Type: System.Object
A user-defined object containing information about the write operation. This object is passed to the asyncCallback delegate when the operation completes.

Return Value

Type: System.IAsyncResult
An IAsyncResult object indicating the status of the asynchronous operation.


credential is null.

- or -

targetName 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.

This method is asynchronous and does not block while the operation completes. To block until the operation completes, use one of the AuthenticateAsClient method overloads.

The asynchronous authentication operation must be completed by calling the EndAuthenticateAsClient method. Typically, the method is invoked by the asyncCallback delegate. For detailed information about using the asynchronous programming model, see Calling Synchronous Methods Asynchronously

If the authentication fails, you receive an AuthenticationException or an InvalidCredentialException. In this case, you can retry the authentication with a different credential.


The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: ExternalThreading. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

.NET Framework

Supported in: 4

.NET Framework Client Profile

Supported in: 4

Windows 7, Windows Vista SP1 or later, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later)

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