Public Overloads Sub AuthenticateAs( _
   ByVal credentials As NetworkCredential _
) 

public void AuthenticateAs( 
   NetworkCredential credentials
)

Guid iid = Guid.NewGuid();
using (RpcServerApi server = new RpcServerApi(iid))
{
    server.AddProtocol(RpcProtseq.ncacn_np, @"\pipe\testpipename", 5);
    server.AddAuthentication(RpcAuthentication.RPC_C_AUTHN_WINNT);
    server.StartListening();
    server.OnExecute +=
        delegate(IRpcClientInfo client, byte[] arg)
        {
            Assert.AreEqual(false, client.IsImpersonating);
            using (client.Impersonate())
            {
                Assert.AreEqual(true, client.IsImpersonating);
                using (client.Impersonate())
                    Assert.AreEqual(true, client.IsImpersonating); 
                //does not dispose, we are still impersonating
                Assert.AreEqual(true, client.IsImpersonating);
            }
            Assert.AreEqual(false, client.IsImpersonating);
            return arg;
        };

    using (RpcClientApi client = new RpcClientApi(iid, RpcProtseq.ncacn_np, null, @"\pipe\testpipename"))
    {
        client.AuthenticateAs(RpcClientApi.Self);
        client.Execute(new byte[0]);
    }
}

Dim iid As Guid = Guid.NewGuid()
Using server As New RpcServerApi(iid)
    server.AddProtocol(RpcProtseq.ncacn_np, "\pipe\testpipename", 5)
    server.AddAuthentication(RpcAuthentication.RPC_C_AUTHN_WINNT)
    server.StartListening()
    server.OnExecute += Function(client As IRpcClientInfo, arg As Byte()) Do
        Assert.AreEqual(False, client.IsImpersonating)
        Using client.Impersonate()
            Assert.AreEqual(True, client.IsImpersonating)
            Using client.Impersonate()
                Assert.AreEqual(True, client.IsImpersonating)
            End Using
            'does not dispose, we are still impersonating
            Assert.AreEqual(True, client.IsImpersonating)
        End Using
        Assert.AreEqual(False, client.IsImpersonating)
        Return arg
    End Function

    Using client As New RpcClientApi(iid, RpcProtseq.ncacn_np, Nothing, "\pipe\testpipename")
        client.AuthenticateAs(RpcClientApi.Self)
        client.Execute(New Byte(0) {})
    End Using
End Using