Q:

How to pass an array of structures through Postback? 

I have the following structure:
private struct S_indiv
{
    public int[] x;
    public int s;

    public S_indiv(int[] p1, int p2)
    {
        x = p1;
        s = p2;
    }
}

and array:
private static S_indiv[] ind;

How can I pass this array through Postback?

A:

Based on your comment response, it sounds like you just want to keep it around for that single page lifecycle. If so, all you need to do is make a member variable on your page class:
protected S_indiv _myData;

If you create or load it in your button event, simply assign to that member variable instead. Then, for the rest of that lifecycle (including OnPreRender, etc), you can access that member variable and get the data.
If that is not what you want, please clarify with a timeline how you want to use this data.

