Hi Sanjay
I got the solution.
The hidden fields need to initialize at client side also i.e., in javascript. So after this code
hdnPaxID.Value = string.Join(",", lstCabins.Select(n => n.Passenger));
I've called javascript function which will update hiddenfield value
function setHiddenFieldValue(hdnPaxID, hdnPaxValue)
{
document.getElementById(hdnPaxID).value = hdnPaxValue;
}
So in my main javascript function, I can get these updated value.
Conclusion: If hiddenfield value to be use at client side then it needs to initialize at client side only.
I don't know how it happens but it works for me.