Refresh A Page Without Postback?

There is a asp:Label in the page for showing message from server.

The message can be sent by server at any time.

I added a handler to update the Label's Text, like following:

void MessageReceived(object senders, EventArgsMessageReceived e)
{
lblMessage.Text = e.Message;
lblMessage.DataBind(); //To show the message
}

I am sure the break point of 'lblMessage.Text = e.Message;'' is hitted.

But the DataBind() seems not work, and the label isn't updated.