for (int i = 0; i < Application.Count; i++)
{
//if (userlist[i] == null)
// userlist.RemoveAt(i);
if (Application[i].ToString()==null)
Application.RemoveAt(i);
}
// int index = Application.IndexOf(LoginName.Text.Trim());
for (int i = 0; i < Application.Count; i++)
{
if (Application[i].ToString()==LoginName.Text.Trim())
{
Response.Write("该用户已经登录,不可以重复登录 !");
return;
}