Write session in VB/C#, read session in Javascript - What is Proper Way?

I've got an app that gets some information and stores it into 2 variables, then writes this information to a session variable, all via VB.

I then try to retrieve the session variable via Javascript and C#.

It works, but it's flakey. 1.) am I doing this correctly? 2.) is there a better way?

Here's the code that writes the session variable out:

Session.Add("Session1", it1
Session.Add("Session2", it2)

I also used

Session("SessionKey") = 123

Then I read back via JavaScript using...

user_id = '<%=Session("SessionKey")%>';

The problem is although SessionKey comes back ok, reading the others does not when I read back in the same fashion...

the_item1 = '<%=Session("Session1")%>';

the_item2 = '<%=Session("Session1")%>';

When these lines are added, it messes up the Javascript and makes the lines after it not work properly (some lines execute, some don't).

So 2 questions:

1.) What is the proper way to handle session variables across VB/C# to Javascript?

2.) Someone mentioned that you shouldn't use the OnLoad= in the <body> tag, because it sometimes fires sometimes doesn't or is unreliable in some way. Is that true? If so, what is the proper way to handle onload to exectute a Javascript function on page load. This may account for some of the issues I am seeing.

Thank you