$('#textBoxId').keydown(function(e) {
  if(e.keyCode === 13) {
    e.preventDefault(); 
    $('#buttonId').trigger('click');
  }
});

or - not tested:

$('#textBoxId').keydown(function(event) {
    var e = event || window.event;
    var keyCode = document.all ? e.keyCode : e.which;

    if (keyCode == 13) {
        e.preventDefault();
        $('#buttonId')[0].click();
    }
});

http://stackoverflow.com/questions/494076/jquery-and-asp-net-forcing-button-click

ASP.Net Trigger button with Enter

JavaScript