Web Forms :: Variable Initializing Again And Again On Form Submit?

Initially before page load I declared list string variable

List<string> Emails = new List<string>();

Then I am adding value in for each as

Emails.Add(Convert.ToString(item["E-mail Address"]));

I checked value are ading properly. Then on btn_click event I am retrieving value as

foreach (string emailid in Emails
{
Response.Write(emailid .ToString());
}

Nothing is displaying, it seems on form submit list string is initializing.